July 09, 2007
Apnea in Plush Jacket
Apnea of Apneatic.com wears fake fur under an incandescent spot light.
Posted by digital artform at 04:34 PM | Comments (0)
July 02, 2007
Liz Ashley Unrestrained
Posted by digital artform at 10:10 AM | Comments (0)
June 29, 2007
Kumi with Shamisen
Kumi poses with a Japanese Shamisen
Posted by digital artform at 11:15 AM | Comments (0)
June 26, 2007
Liz Ashley II
Posted by digital artform at 09:25 PM | Comments (0)
June 25, 2007
Liz Ashley in Vinyl
An experiment in overexposure. The incomparable Liz Ashley in yellow vinyl back lit by a large frosted glass door.
Posted by digital artform at 09:44 PM | Comments (0)
June 22, 2007
Apnea
The beautiful Apnea of Apneatic.com
Posted by digital artform at 09:19 PM | Comments (0)
June 18, 2007
Complementary Gels forming Neutral Light
10 degree grid and warm light on face. 20 degree grid and cold light on face and torso. Where they combine the light is relatively neutral. The falloff is cold.
Posted by digital artform at 08:26 PM | Comments (0)
Feathered Light from Honeycomb Grid Strobe
On the left I placed a stobe at a high angle, fitted it with a 20 degree honeycomb grid from White Lightning, and aimed it at the face of my mannequin. As one would expect, a pool of light surrounds the face.
Next I tried feathering the light. I aimed the high angle 20 degree gridded strobe at the mannequin's chest. The result? Even illumination down the body.
Why?
The face receives dim edge light but is also closer to the source.
Posted by digital artform at 08:01 PM | Comments (0)
June 03, 2007
Courtney with Red Lace Parasol
Courtney Cruz in the Mojave Desert under the shade of a red lace parasol.
Posted by digital artform at 01:54 PM | Comments (0)
June 02, 2007
Kumi in the Desert
Internationally famous latex fetish model Kumi Monster on a dry lake bed in the Mojave Desert.
Posted by digital artform at 02:24 PM | Comments (0)
April 19, 2007
Portrait of Marissa
I bounced light off a cinder block wall to make this portrait of Marissa Spokes. A white bounce card behind her provided some fill.
Posted by digital artform at 09:44 AM | Comments (0)
March 31, 2007
Portrait of Scar 13
A portrait of Scar 13 [18+ NSFW]. Makeup by Chelsea Wildeye.
Posted by digital artform at 01:24 PM | Comments (0)
March 29, 2007
Kumi Unmasked
Internationally famous fetish model Kumi Monster unmasked. Fresnel hot lights. Nikon D200.
Posted by digital artform at 11:57 PM | Comments (0)
Jasmine Seduces Natalie
Jasmine Worth whispers to Natalie Addams by window light. Nikon D200.
Posted by digital artform at 10:21 AM | Comments (0)
March 27, 2007
Vagabond Lighting Experiments
I was playing with my Vagabond portable power supply in an alley.
A cinder block wall makes a nice large softbox.
Posted by digital artform at 11:02 PM | Comments (0)
March 15, 2007
Scar Arises
Scar arises. Latex by Syren.
Posted by digital artform at 10:04 PM | Comments (0)
March 14, 2007
Kumi Faceless
Kumi Monster at repose in the darkness. Latex by Syren.
Posted by digital artform at 10:05 PM | Comments (0)
March 13, 2007
Courtney Captures Jasmine
Courtney Cruz captures Jasmine Worth
Posted by digital artform at 11:45 PM | Comments (0)
February 25, 2007
Island Girl
Scar of [NSFW 18+] Scar13.com under fresnel hotlights.
Posted by digital artform at 10:58 PM | Comments (0)
February 11, 2007
Crash! on Planet Tiki!
A photo I took of [18+ NSFW]Scar. Rocket Pack constructed for me by Mark Poutenis. Door panels by BJ Winslow of Dapper Cadaver. Photo by Joseph Francis.
Posted by digital artform at 07:30 PM | Comments (0)
January 23, 2007
Young Femme Fatale
Portrait of Jacqueline Porcile in evening gown. DeSisti lamps. Nikon D200. Hair and Makeup by Rocio Gonzalez and Ping Tan "Icey"
My first stab at using Fresnel hot lights.
Posted by digital artform at 11:41 AM | Comments (0)
December 08, 2006
Amber with Cake Frosting
I had this idea that cake frosting might make a novel model makeup effect. Model Amber Kendrella. Makeup by Geeta Dastyar. Frosting by Jennifer Orr. Mola beauty dish. Nikon D-200
Here are some more photos from the Cake Frosting Model Makeup shoot
http://img.photobucket.com/albums/v228/jfrancis/Amber/Amber_3177_c_600.jpg
http://img.photobucket.com/albums/v228/jfrancis/Betcee/Betcee_3124_600.jpg
http://img.photobucket.com/albums/v228/jfrancis/Betcee/Betcee_3127_600.jpg
http://img.photobucket.com/albums/v228/jfrancis/frosting/frosting_3242_600.jpg
http://img.photobucket.com/albums/v228/jfrancis/frosting/frosting_3288_600.jpg
Posted by digital artform at 09:32 AM | Comments (0)
November 05, 2006
Portrait of Anja
Posted by digital artform at 09:14 PM | Comments (0)
October 15, 2006
Sekonic L-558R / Nikon D200 Exposure Test 2
As indicated by the meter. Lumisphere ball out on an overcast late afternoon.
1/3 stop brighter.
2/3 stop brighter.
1 full stop brighter.
It looks like a half stop at most is the adjustment in this test.
Posted by digital artform at 06:23 PM | Comments (0)
Sekonic L-558R / Nikon D200 Exposure Test 1
I've been using my Sekonic L-558R to set the exposure for my Nikon D200. So far I seem to be habitually underexposing the images more than I'd like. Above is a Gretagmacbeth grayscale card exposed as indicated by my meter in incident mode. I have included histograms in the images.
The same scene with the camera opened up 1/3 of an f-stop.
2/3 of an f-stop brighter.
At a full f-stop brighter the white on the card, which is supposed to be at something under 94% reflective, is off the histogram.
Posted by digital artform at 02:11 PM | Comments (0)
October 12, 2006
Layla Jade
A portrait of Lyla Jade with my new White Lightning beauty dish.
Posted by digital artform at 08:43 PM | Comments (0)
October 11, 2006
Anyssa Sings v 2.0
Another take from the set.
Posted by digital artform at 09:41 PM | Comments (0)
August 30, 2006
Model Photography
In preparation for some upcoming projects of mine involving photography and the Maxwell Renderer, I thought I'd try a visit to a photo shoot.
This was a group shoot, and I wasn't in control of either the lighting or the model direction, but I did gain some experience in exposing using photographers strobes.
The shoot itself presented certain challenges. The models were good at posing and mainly self directed, which placed the photographers more in the position of paparazzi, all competing to get a shot. It seemed to me that every time a model would strike a good pose, another photographer would either rise into my frame or beat me in sending his wireless radio signal from his camera to the strobe, causing me (since the light takes a moment to refresh) to miss the flash.
Not having ever worked with one before, I was concerned at first about how to best meter and expose for the strobe, but I soon figured out that the light wasn't going anywhere, and neither, for the most part, was the model, so the lighting conditions were fairly constant. Since we were shooting digital, I could just manually set the camera shutter speed to no higher than 1/250 - the synch speed of the Nikon D200, and just take a guess at the aperture. After a test shot or two, the lcd screen and histogram told me enough to make the necessary aperture adjustments.
Is that really all there is to it? Sure seemed that way.
I have a Model Mayhem portfolio now.
Here's a conversation I had at Nikonians about this.
Posted by digital artform at 11:06 PM | Comments (0)
June 16, 2006
Boujou Test of Nikkor 50mm f/1.8 for Maya
After testing my Nikkor 85mm f/1.4 through Boujou 3 and getting a lens solve of around 50mm, I decided to test an actual 50mm lens.
I mounted a Nikkor 50mm f/1.8 lens on my Nikon D200 and moved it forward step by step toward a white board on which I had marked a few tracking crosshairs in erasable ink.
]
Boujou 3 appeared to perform well, reporting a point cloud revealing a push-in across a flat, vertical wall-like surface.
Maya 7 reported a camera focal length of a bit under the 50mm lens I had in fact used. Normally I'd be pleased at such a seemingly accurate answer, but I'm not quite sure how to interpret this data.
The problem is my Nikkor 85mm f/1.4 also solved out at around 50mm.
Further testing with other lenses is warranted.
Posted by digital artform at 08:07 PM | Comments (0)
Boujou Test of Nikkor 85mm f/1.4 for Maya
I shot a few frames with my Nikon D200 using my new Nikkor 85mm f/1.4 AF-D lens and ran the images through Boujou 3 to see how it and Maya would see the lens.
I told Boujou that the lens focal length was 85mm, and that the film back was 23.6mm x 15.8mm which is, as far as I could research, the active area of the Nikon D200 APS-C chip.
The free move yielded a nice, well-defined point cloud -- you can easily see the curved chair back and flat wall beyond -- so I expected a lens solve close to 85mm.
Instead of an result close to 85mm, what I got from Boujou was a virtual lens with a focal length just under 50mm.
Maybe long lenses don't produce enough parallax for a closer solve.
Maybe more extensive testing on a longer sequence is required.
Since I intend to combine my Nikon D200 photography with rendered backgrounds from Maya and Maxwell, I'd like to get a good handle on how to best match lenses.
Posted by digital artform at 05:25 PM | Comments (0)
April 24, 2006
Bright-for-Dark Photography
I plan to make some dramatically-lit photos (combined with Maxwell renders). As a prelude to this work, I an experimenting with some issues related to photographic exposure. My goal in this experiment is to create the illusion of a spotlight illuminating a figure on an otherwise dark stage without actually having a particularly dark stage. It's nothing new, but I want to try it myself.
The photograph above represents a human figure on a stage under subdued window lighting.
Here's the same set, but now I'm "whacking" the figure with an overpowered key light. This adds even more light to the set.
When I expose for the new bright key light, it's as if I've effectively "darkened the room."
By going from a one second exposure to a 1/250th second exposure (for a given aperture) I have darkened the scene by 8 f-stops. I even seem to have reversed the lighting; the window light is no longer apparent at all. What's more, I can have the depth of field and short shutter speeds not normally associated with low light photography - if I choose.
Photograph doesn't always have to "mimic" how you perceive the scene to be. I remember one day I visited a taping of The David Letterman Show. I was struck by how pale, washed out and desaturated the set and everyone on it looked in person, and how richly contrasty and lustrously saturated it looked on the monitors.
Posted by digital artform at 01:46 PM | Comments (0)
March 27, 2006
Nikon D200 Black and White Photography
An experiment to see what differences exist between originating digital black and white photography using Nikon D200 in-camera settings vs shooting in color and converting to black and white as a post process.
From what I can see, if you have a program like Photoshop, there is little difference, and little point in limiting yourself by using the in-camera black and white setting.
Original color image.
Original black and white image.
Black and White image derived from color in Photoshop using Image > Mode > Grayscale.
For sophisticated control in Photoshop over black and white images you are best served by shooting in color and using the new channel mixer.
Posted by digital artform at 07:18 PM | Comments (1)
March 19, 2006
High ISO Noise Reduction by Image Averaging
If you are photographing a stationary subject with a stationary camera you can reduce grain or high ISO noise by averaging together multiple seemingly identical images.
I set up a still life under relatively low light conditions and photographed it eight times in a row at 1600 ISO with a Nikon D200 mounted on a tripod.
Here is a 100% crop of the 1600 ISO image. It's noisier than I'd like it to be.
I have now taken all 8 images and stacked them up in Photoshop CS2 in layers 0 through 7. Let's see what happens when we average them together.
First I set the opacity of layers 7, 5, 3, and 1 to 50% Next I merge them down in pairs -- 7 to 6, 5 to 4, 3 to 2, and 1 to 0. I now have 4 layers in a stack labelled 6, 4, 2, and 0
Here's what a pair of layers looks like when averaged together. You can already see a noise reduction.
Let's continue, repeating the process.
I'm now setting layers 6 and 2 to 50% and merging down in pairs -- 6 to 4, and 2 to 0. I now have 2 layers in a stack labelled 4 and 0.
Let's repeat the process one final time.
I set layer 4 to 50% and merge it down onto 0.
Look above. Look below. You can really see a difference.
Here's the original noise again -- just for comparison.
You can do grain reduction through image averaging on moving footage as well, just as long as the subject and camera are still. That may not sound useful, but the technique does have its place:
I had occasion to use this technique in the feature film Independence Day. There's a shot of The Empire State Building down at the end of an avenue waiting to explode. The model miniature footage was excessively grainy. I had the compositor replace every frame of the footage with a running average of the previous 20 frames. It made for a great grain removal technique. Once the model exploded, we returned to the grainy element, but it was so mixed with fire and flying debris that the grain wasn't objectionable.
Fun Idea
If you can steady the frames properly, you can use image averaging to get a better look at that flying saucer footage, or you can demosaic the identity- or nudity-obscuring blocky pixel mosaics sometimes placed on running video. The trick is to be able to get the frames to stack up in perfect register, which may not always be possible.
Additional Links
Reindeer graphics Image Averaging
Posted by digital artform at 07:23 PM | Comments (6)
March 15, 2006
Nikon D200 Zone System Dynamic Range
I'm curious to see what kind of dynamic range my new Nikon D200 has. As an experiment, I'm taking a series of exposures of a stucco wall as described in Ansel Adams's book, The Negative
The purpose of the exposure series is to place the stucco wall on various zones from Zone 0 to Zone X in order to see how the camera responds. Each "zone" represents one f-stop more or less exposure. Zone V is, by convention, the middle of the scale. It represents an 18% reflective gray card.
The basic idea of the Zone System can be stated as follows:
See something you wish to photograph. Pick a region in that scene. Meter it. the meter (by design) will tell you how to make that region fall in Zone V (middle gray). Decide for yourself onto which zone you would like that region to fall. Adjust your camera accordingly (ISO, shutter speed, aperture, or a combination of the three) so as to place the metered region onto the desired exposure zone. The other regions in the image will fall onto higher or lower zones accordingly, preserving their relative relationship to the metered area (unless you alter contrast in the developing process, in the case of film, or in the computer, in the case of digital photography).
My Results
I photographed a pinkish stucco wall in the shade of a building, taking care to place it on various zones. All photos were taken with a Nikkor 50mm 1.8 lens and a Nikon D200 in aperture priority mode. I set the aperture to f/11 and used exposure compensation to ramp the shutter speed up and down on one stop intervals.
The text that follows is what Ansel Adams expects in each zone. The photos are what I actually got. The images were shot in raw format and converted to jpeg using Photoshop CS2 set to a high (60%) -- but not very high -- quality setting.
Zone 0 - total black in print. My own Zone 0 test resulted in virtually total black. I'm not bothering to post it.
Zone I - effective threshold. Slight tonality. No visible texture - although in my test I do see texture, which tells me that on my Nikon D200, Zone I could be used as a dark Zone II -- a place to put subtle, dark, yet still somewhat discernable shadow detail.
Zone II - first suggestion of texture.
Zone III - average dark materials showing adequate texture.
Zone IV - average dark foliage or stone. Normal shadow value for caucasian skin in sunlight.
Zone V - middle 18% gray. Clear northern sky, dark skin, gray stone, weathered wood.
Zone VI - average caucasian skin in sunlight. Shadows on snow in sunny landscapes. Light stone.
Zone VII - very light skin. Light gray objects. Snow in acute sidelighting.
Zone VIII - whites with texture and delicate values. textured snow. Highlights on caucasian skin. If I wish to expose for highlights and still preserve some detail in them, then it would appear I can place them as high as Zone VIII, possibly as high as EV +3.0, but not much higher -- depending on the local range within the highlights.
Zone IX - white without texture approaching pure white.
Zone X - pure white -- as was my image. I didn't bother to upload it.
Conclusion
My results agree closely with Ansel Adam's expectations, with the exception that i got a little more texture than I expected in Zone I.
I'm pleased with the performance of the camera.
Some Nikonian Forum Interaction
D200 Dynamic Range Test per Ansel Adams
Exposing To The Left and Ansel Adams's Zones
The Zone System as it relates not to Photography, but to Painting
I see a natural crossover between the ideas of the Zone System and the approach master painter Craig Mullins uses in his approach to painting. He reveals his thought process on this forum (under the name spooge demon)
I excerpt his comments below:
"Decide what is in light and what is in shadow and don’t mix them up. Think like a comic artist. Two values, but if they are well thought out and designed and drawn they can look totally real. Think like that, but instead of making the light white and the shadow black, make the light a 7 and the shadow a 3. Then go ahead and use 5-10 in the light and 1-3 in the shadow to pull out sub forms. DO NOT use 1-5 in any part of the light, or use 5-10 in any areas of the dark. Keep you edges a little softer in the shadows, a little sharper in the light, you are done. (0 is black, 10 is white) Deciding what is in shadow and light for a particular object is pretty hard in words. I will leave that up to you and that is 99 percent of the struggle."
Posted by digital artform at 07:23 PM | Comments (0)
January 01, 2006
Nikon D200 Banding
I'm concerned about this Nikon D200 banding artifact many (including me) are seeing. Some attribute this problem to blooming. It's not, as far as I can see, typical blooming. Many have taken to calling it banding, even though banding normally refers to posterization due to insufficient color bit depth. Silkypix calls it geometric noise, and provides a geometric noise NR utility.
There are discussions about the issue in several prominent places:
Nikonians.org - D200 and banding
Nikonians.org - D200 Banding II
Nikonians.org - D200 Banding III
Fredmiranda.com - D200 banding is real
DPReview.com - D200 banding noise issues
"I've done testing to confirm whether the reported "vertical banding" issue is for real, and can confirm it exists under given circumstances, the description of which is in the forthcoming review. (Expected around January 10, 2006)" - Bjørn Rørslett
KenRockwell.com Nikon D200 Striping, Vertical Stripe, Banding and Corduroy Effect
(If my camera's banding were as rare as Ken Rockwell's I wouldn't have sent it in.)
On an encouraging note:
This person Chris Maytag had a camera which exhibited the vertical noise "banding" problem, and I don't think you can attribute this particular example of it to blooming or poor exposure on his part, as is often the case with other photos.
http://flickr.com/photos/spincycle/74270369/
In this thread he claims that replacing the camera seems to have alleviated the problem:
http://www.flickr.com/groups/d200/discuss/141067/
If my own operator error is causing my problems, I hope I soon learn to avoid them. If this is a hardware or firmware problem, I may need to get my camera repaired or replaced.
UPDATE 1/5/2006
I contacted Nikon and uploaded the full resolution original .nef of this image:
http://img.photobucket.com/albums/v228/jfrancis/D200Banding/D200Banding_X1.jpg
After examining the image they requested I send my camera in for servicing.
I had a Return Authorization Number and a shipping label from B&H camera, and I could have sent it back to them for a refund and walked away, but I chose to send it to Nikon instead.
Why?
1) I believe in the camera and in Nikon.
2) I want a D200 sooner than later, and they are hard to come by.
3) Any new camera I might find in the near future could have the same issue.
4) This camera will get Nikon personal attention.
Call me crazy for opting for servicing over a refund from the retailer, but that's what I'm doing.
I'm confident that this problem will be ironed out soon.
UPDATE 1/7/2006
An opinion is emerging on the internet that D200 banding artifacts generally only occur in badly exposed pictures, and are therefore of no concern to "good" photographers. Anyone who has ever made a Paul Debevec HDR radiance map for computer graphics purposes will, however, recognize that some intentionally "bad" photography is a necessary part of the process of creating High Dynamic Range images, and will want their D200 to be corduroy-free.
UPDATE 1/10/2006
My camera arrived at Nikon in El Segundo today for evaluation and possible service. I expect it back in around 7 - 10 days. If it is serviced, I'll shoot a setup like the one above again and see to what extent the problem is solved.
UPDATE 1/13/2006
Here are some additional threads of interest:
A Discussion of Possible Hardware Fixes
A Preview of Bjorn Rorslett's Evaluation
UPDATE 1/15/2006
Nikon D200 Digital Camera Reviewed by Bjørn Rørslett
A Photoshop CS2 Action Script designed by M. C. Schuster to fix banding
UPDATE 1/18/2006
Thu Jan 5: FedEx D200 to Nikon El Segundo
Fri Jan 6: D200 arrives per FedEx
Tue Jan 10: D200 logged in "officially" arrived per Nikon
Wed Jan 18: (ongoing) waiting for parts.
Service Repair Rank B2 - "If Parts are Available"
Repair Category B2 - "Moderate Repair. Major Parts Replaced"
Thu Jan 19: Status now described as "In Shop"
Fri Jan 20: Status updated to "Bill" - Order Confirmed
Mon Jan 23: Camera has arrived back home - will begin testing tomorrow.
Tue Jan 24: I reproduced the setup that caused banding so easily for me before - a chair in front of an open window - and I would have to say I now consider the banding fixed. I'll repeat this at the bottom of this posting, and I'll elaborate in another posting.
*This work is covered under warranty, however. The bill amount is $0.00
According to the notes I got back from Nikon, nothing seems to have been replaced. The service was described as "ADJ IMAGE CONTROL"
UPDATE 1/20/2006
One individual reports Banding NOT fixed by Nikon El Segundo ... this is troubling news to me.
Imaging Resource - Nikon D200 User Report - scroll down to the section marked Footnote: What Causes This? for some speculation.
UPDATE 1/22/2006
Someone has a Nikon D200 Banding Fixed experience.
A responding commentor has no such luck himself.
UPDATE Tue Jan 24
I reproduced the setup that caused banding so easily for me before - a chair in front of an open window - and I would have to say based on my initial tests I now consider the banding fixed.
I couldn't resist trying some additional tests. The camera now passes just about every test it would have failed before, with this one exception . . .
It is possible under extreme circumstances to induce what Bjørn Rørslett calls Type I Banding.
UPDATE 2/5/2006
Nick Karpowicz provides a Fourier Analysis Image Processing solution to Nikon D200 Banding implemented in MATLAB. I havn't look at this in any detail yet, and I don't have MATLAB software either, but it looks interesting.
UPDATE 2/10/2006
Nikon USA acknowledges and discusses banding according to this forum post.
I had a discussion with someone unrelated to Nikon who shared with me his personal beliefs on the matter:
1) Readout on the D200 chip are in pairs of lines. The chip is made by Sony with an RGBE (Red-Green-Blue-Emerald) Bayer pattern and thus does a 2-line at a time serpentine readout.
Thus lines 0 & 1 read out together, lines 2 & 3 read out together, etc.
2) Readout alternates between the top and the bottom of the chip: 0&1 go UP, 2&3 go DOWN, 4&5 go UP, 6&7 go DOWN, etc. This means that blooming will have a tearing (or as you've guys called it a "Corduroy") pattern on horizontal or near horizontal edges, both on the tops and on the bottoms of those edges.
3) Noise in CCD cameras is always higher on the side of the chip that has the longest readout. Since half of the lines are reading out in the upwards direction and half are reading out in the downwards direction, unless you're looking at the middle of the image, the background noise between pairs of lines will not match. This is even more evident at high ISO values where there is higher amplification on the background noise.
4) CCD logic does NOT have an A/D on chip. Instead the CCD is connected (via solders & wires or traces) to a more standard Flash A/D. If there is a bad connection (or even a marginal one) you can get induced noise. If that is worse in the UP direction than the DOWN direction, you could see this as a preferential noise problem. If one of those traces was acting like an unshielded antenna (which can also happen sometimes) you might see a frequency pattern that could be removed by an FFT.
UPDATE 2/14/2006
DigitalReview.ca Nikon D200 Digital SLR Banding Issue FAQ
According to the info at the link above, Nikon says current production models don't exhibit (type II & type III) "long banding." The article (and the FAQ from Nikon) doesn't mention (type I) "short banding."
UPDATE 2/16/2006
According to this post on dpreview, in Croatia (at least) the fix involves a hardware replacement as well as a recalibration.
UPDATE 2/19/2006: The Other Side of Banding
I thought I'd dig up one of the many test pictures I took with my faulty camera - prior to its repair - that were intended to provoke Nikon D200 banding but failed to do so.
I put these images here to show "the other side of banding," and to try and lend some perspective to the issue.
Yes, you could say that the camera's performance was uneven, in that it often did not band, and that it was hard to predict when it would and when it would not, but I wanted to show that even a faulty, "banding" camera performed extremely well most of the time.
3/21/2006
A pretty good final word on the banding matter in this Nikon D200 Review by Thom Hogan
Posted by digital artform at 07:13 PM | Comments (21)
December 04, 2005
Lens Correction in Photoshop CS2
Photoshop CS2 contains a versatile tool for correction certain problems caused by camera lenses. You can find it under Filters > Distort > Lens Correction.
One option for this tool brightens and darkens the corners of images in order to compensate for lens vignetting.
The nice thing about this tool is that it acts as if all images are actually square. The lens vignette tool is not fooled by widescreen aspect ratios. Lenses are round, and so is the vignette correction.
You'd think Photoshop would adopt this outlook for the other related tools as well. Oddly enough, it does not.
Here's a widescreen image being subjected to Photoshop CS2's barrel distortion / pincushion distortion correction tool.
Notice how the effect is nailed to the corners of the image. That's an odd thing to do. Lenses are round. Barrel distortion and pincushioning should be nailed to the corners of a virtual square image, not the true corners of the actual widescreen image.
It seems a more sensible approach would be to use the Image > Canvas Size options to extend the widescreen image onto a square canvas before applying lens distortion effects.
Posted by digital artform at 10:28 PM | Comments (0)
November 19, 2005
Canon 5D vs Nikon D200
The Canon 5D versus the Nikon D200. I know, I know. These cameras aren't intended to compete head-to-head in the marketplace. And yet this is how it seems to break down for me.
I'm looking for a good DSLR. I probably can't go wrong with either one.
I want sharp photography at a high resolution. I also think I'm going to be combining my photography with photorealistic 3D CG (probably from the Maxwell Renderer), so I think that as much as I like the look of shallow depth-of-field, I will, in practice, need deeper DOF. The smaller sensor of the Nikon lends itself to deeper DOF.
But I want to take some moody photographs in baroque, theatrical lighting conditions and combine them with 3D. For that reason, I like the low noise at high ISO characteristics of the Canon 5D.
But the Nikon D200 is half the price.
But the Canon shoots at over 12 megapixels, which is over the magic number (for me) of 4096 pixels wide. Why do I care about 4096 pixels? It's probably just a fetish, but when I used to create 8x10 transparencies of computer graphics for print, 4096 pixels was always the recommended resolution for the 10" dimension. 4096 pixels is also a minimum width for some large movie formats. As a visual effects practitioner I'm sometimes called upon to produce large format work, so for texture maps or backgrounds I like the megapixels.
But at 10.2 MP the Nikon d200 is pretty high resolution, too, and it's half the price. Plus it's got a sturdy build and better weather sealing from what I understand.
But the Canon 5D shoots full frame. Canon has great lenses, and Canon is a monster company on the rise. If they are pushing FF, it probably has a future. Plus the weather sealing is plenty good enough.
But the Nikon D200 has lighter lenses, and the smaller sensor uses the sweet spot of the lens, cropping off the dark, blurry corners.
But the Canon L glass is good, and Photoshop can correct the darkish corners of some pictures that will arise with some lenses at some apertures.
But the Nikon d200 has great lenses too, and more in development. And did I mention the D200 body is half the price?
But the Canon 5D is on shelves now.
But the Nikon D200 soon will be.
ADDITIONAL LINKS
Nikon D200 Review Roundup from Digital Camera Tracker
Canon EOS 5D Review Roundup from Digital Camera Tracker
Nikonians.org thread comparing the two (Nikon-oriented, of course)
Japanese site with similar (virtually side-by-side) photos taken first from the Nikon D200 and then the Canon 5D. It looks like the Canon performs with lower noise at high ISO's. Commentary on this comparison from a Nikon perspective here.
UPDATE 12/25/05
. . . and we have a winner.
UPDATE 1/15/2006
Nikon D200 Digital Camera Reviewed by Bjørn Rørslett
UPDATE 2/11/2006
Rumors are starting to emerge that the next Canon camera is the Canon EOS 35D
UPDATE 10/9/2006
The original math I did was this: Canon 5D at $3300? Or Nikon D200 at $1700? - 85% of the camera for half the price. The real question to ask - once you've spent a bunch on lenses and lights - is, "Do I want to spend $10000 on photography or $11700 on photography?"
Posted by digital artform at 03:50 PM | Comments (6)
December 26, 2004
Telephoto and Wide-angle Lenses
Telephoto lenses don't "flatten" a scene, they merely crop it tighter. Wide angle lenses don't "distort" a scene, they merely crop it looser.
Here is a collection of photographs (copyright Ian Britton, FreeFoto.com) taken from the same camera position but with lens focal lengths of 300mm, 200mm, 100mm, 50mm, 35mm and 24mm.
Let's see what happens when we carefully compare one to the next.
The image taken with the 200mm can be found sitting within the image taken with the 300mm lens.
The image taken with the 100mm lens sits neatly within the image taken by the 200mm lens.
The same relationship holds true for the 50mm lens photograph and the 100mm lens photograph.
The 50mm lens captures the same scene as does the 35mm lens, only the longer lens crops the scene more tightly.
Even the widest lens of all in our test, the 24mm lens captures an image which at its center is distorted no differently than the image captured by any other lens.
Within the limits of image resolution, you can simply crop a more telephoto image out of any other image.
Philip Greenspun puts it well when he says, "If film and lenses were perfect... you would need only one lens!"
Not convinced? The illusion that wide angle lenses cause distortion is a strong one. For an explanation of why people cling so tenaciously to this belief, read more here:
http://www.digitalartform.com/lenses.htm
Posted by digital artform at 11:31 AM | Comments (18)
October 20, 2004
Smear Now - Or Smear Later
If you work with pixel addresses instead of the pixels themselves, you can smear (or ray trace) now, and decide which image it was you were smearing (or refracting) later.
Take a linear horizontal red grad and add it to a linear vertical green grad. This will give you an image of absolute pixel addresses - or what some might call an image of UV values.
In such an image, you can calculate any pixel's position if you know its color, and you can determine its color if you know its position. That's what makes it an image of absolute pixel addresses.
Grab a hunk of these absolute pixel address from anywhere you like and move them to any other place on the image that you like.
Next subtract the modified image of absolute pixel addresses from the original image of absolute pixel addresses. This will give you an image of relative pixel displacement offsets.
Here are the relative pixel offsets. Notice that any chunk of addresses that was moved horizontally became a shade of red with an intensity proportional to the distance it was moved. Any chunk of addresses that was moved vertically is green. Those that were move diagonally are yellow.
You can move the pixel addresses using any technique you like. Put a refractive object in front of the original UV image and raytrace into it. Or smear it using a Photoshop tool, if you like, which is what I did in the example above.
After you subtract the smeared UV image from the original UV image, you'll end up with a displacement map of pure relative smears.
Here's another example.
After the subtraction, it looks as above.
Using this technique, you can smear in "address space" and then later apply the smears (or refractions or what have you) to an image after the fact.
What's more, you can change your mind later, and swap one image for another.
One last thing: there are some issues with using the difference blend mode in Photoshop. That blend mode returns absolute values, even in cases when a true subtraction would return negative numbers. There are some issues with Photoshop displacement as well. Instead of using negative numbers, zero, and positive numbers to control displacement, Photoshop uses dark colors, middle gray, and bright colors to control it.
If you want to explore this yourself, you might be better off using Shake, which can handle the negative numbers during internal calculations in a way that Photoshop can't. To see the Shake version in action, check out UV Map Now or UV Map Later.
If you want a better idea of the "gotchas" in Photoshop displacement, the gory details are here
Posted by digital artform at 08:27 AM | Comments (0)
October 18, 2004
Digital Heat Ripple
The 2D digital displacement map techniques in programs like Photoshop and Shake confuse many users. You need to supply these programs with separate red and green displacements, not just a gray displacement.
Here's a square rotated 45 degrees.
Here's some turbulence. This type of image makes a useful displacement map for achieving digital "heat shimmer" or "heat ripple" effects in post production.
Here's the result - a displacement only in the diagonal direction.
Notice how two of the diagonal edges have remained straight. Why? Because they have been displaced in the same direction in which they are already pointing.
The red values of a displacement map control horizontal displacemement. The green values control vertical displacement. The exact method varies from program to program, but in Photoshop, middle red is the "zero displacement" for horizontal motion. Middle green is the "zero displacement" for vertical motion. Darker values go up, or left, as the case may be. Lighter values go down, or right, as the case may be.
Let's work with a new source image. In this case, it's a simple, unrotated square.
Here's red turbulence. It displaces the source image horizontally.
Here's the results of the red turbulence displacement. The overall vertical drop comes from the fact that the green channel is all black. Black is not the null displacement. Middle green (0 127 0) is.
Here's green turbulence. It displaces images vertically.
Here's the results of the green turbulence displacement. Note the overall horizontal shift. This is caused by the fact that the red channel is not set to 127, the null displacement, but to zero, a strong lateral displacement. Overlooking this detail is easy to do!
Here's turbulence in the red channel combined with the zero offset value (127) in the green channel. Remember I'm using Photoshop for this.
Here's the "zero offset" in action.
Finally, here's turbulence in the red channel, and completely unrelated turbulence in the green channel.
This is a good basis on which to build a heat ripple effect.
Posted by digital artform at 01:36 PM | Comments (0)
October 15, 2004
Alpha Channel as a Holdback Matte
When you need to composite soft-edged or motion-blurred 3D CG (which has been rendered over black) over a background, and you don't want matte lines, you will get great results if you use the 3D element's alpha channel as a holdback matte
Most 3D CG is rendered over black. Most 3D CG comes with an alpha channel that precisely fits the 3D foreground element. Here's how to composite that 3D CG over live action using the same image arithmetic that Shake's over node uses.
First negate the 3D element's alpha channel.
Next, multiply the inverted alpha channel times the background image. This causes the alpha channel to hold back portions of the background image, creating a soft hole into which the foreground element can be dropped.
Notice that the foreground is a soft element on a black background that already precisely fits the soft hole in the background.
Finally, simply add the foreground to the hole in the background. In Photoshop, you can find addition well hidden under Apply Image - or renamed as the blend mode Linear Dodge.
Hooray! No matte lines!
Here's a related page on matte lines and transparency mapping:
Transparency Mapping and MATTE LINES:
http://www.digitalartform.com/archives/2004/12/transparency_ma.html
Posted by digital artform at 10:40 PM | Comments (0)
Alpha Channel as a Clipping Channel
Many compositors think of an alpha channel as a "clipping channels" that trims a foreground element from its original context and places it over a background. When they get soft-edged 3D CG rendered over black, their composites always exhibit matte lines. Here's one way to avoid those matte lines.
A key mix can be a useful technique for many compositing tasks, particularly composites known as wipes.
The key mix technique is poorly suited for compositing 3D CG elements that have been rendered over black backgrounds. When used for this purpose, it produces matte lines, those areas of gray haze that surround the foreground element.
Matte lines are caused by an unneccesary multiply that occurs in the key mix compositing process. The multiply occurs between the foreground element and its own alpha channel. One way to improve the results produced by a key mix used in this manner is to introduce a preemptive divide into the process - dividing the foreground by its own alpha channel in anticipation for the multiply which occurs in the key mix.
Many programs (such as Photoshop) do not offer the ability to perform image division. Many other programs, such as Maya, offer division, but perform poorly when called upon to execute the mathematically undefined operation of "division by zero" (which occurs when the image in the dividend contains black pixels). The program Shake is smart enough to skip black pixels. Shake produced the image you see above. Notice how dividing a beauty pass by its own matte (to use "optical printer" terminology) causes the beauty pass to overshoot its matte.
By inserting this preemptive "divide by alpha" into the key mix process, you can force key mixing to be an acceptable procedure for compositing 3D CG. If you must.
Look ma! No matte lines!
I'm not a big fan of this technique. I prefer to treat the alpha channel as a
holdback matte for the background - in Shake this is achieved by using the over node for compositing.
More on that other technique here:
http://www.digitalartform.com/archives/2004/10/alpha_channel_a_1.html
And here's a related page on matte lines and transparency mapping:
Transparency Mapping and MATTE LINES:
http://www.digitalartform.com/archives/2004/12/transparency_ma.html
Posted by digital artform at 07:32 PM | Comments (0)
Creating an Outline
Sometimes it's handy to turn black and white images into smooth outlines. Here's a little recipe for doing just that.
Introduce some grey into the black and white image. One easy way to do this is to blur the image a bit. The bigger the blur, the broader the outline will be.
Make a copy of the original image and invert it.
When the two images are multiplied, wherever either image is black the resulting product is black. Wherever either image is grey, the other image is by necessity also grey, and the product of the multiplication is a dark grey.
If black is represented by an intensity of zero, and white is represented by an intensity of one, then the middle of a blur in a black and white image is a .5 grey.
The product of a .5 grey with itself is a .25 grey. To make a .25 grey look white, you need to brighten it by 400%
Here's the "outline" recipe in action. Black and white 3D turbulence wipes this movie set from "normal" to "icy." All of the gray areas in the wipe have been extracted using the recipe described above and turned electric blue.
Posted by digital artform at 04:34 PM | Comments (0)
Colorize Black & White Art by Keymixing
A compositing technique called a key mix borrowed from the visual effects industry can turn a black and white alpha channel into 2-color artwork. What's more, it captures the subtleties of antialiasing and grays more easily than does Photoshop's magic wand tool.
The idea is to treat the black and white artwork as a key intended to mix two images of flat colors.
Let's say we wish to turn the black and white artwork into red and yellow artwork.
We take the artwork and multiply it by the color red using the multiply blend mode.
Next we take the negative of the artwork (the photographic inverse) and multiply it by the color yellow.
Finally we take the two intermediate stages and add them using apply image > add (It's not a blend mode. You have to hunt around for it) *** UPDATE: Add is a blend mode. It's been renamed Linear Dodge. See comments below.
I think this technique captures the complexities of rough, antialiased, or gray edges better than does the magic wand tool (or other selection methods.)
Posted by digital artform at 12:05 AM | Comments (5)