Mark Antony Smith has nice reviews, with sample images, of Adox CHS 50 ART and Adox CHS 100 ART black and white films.
Category: Extra Geeky
MTF charts demystified
MTF charts are graphs of lens resolution that are meant to give you an idea of how a given lens performs at different points across the frame. (Most lenses are sharpest in the centre and get a bit softer as you go out, and these charts illustrate that characteristic.) They’re easy to read once you understand them, but unfortunately they’re usually explained very badly.
Mike Johnston has put together the first sane and easy-to-understand breakdown I’ve ever seen. Check it out at The Online Photographer.
Kodak Monographs now available for free download
These three Kodak publications are available as PDF downloads from archive.org. As you can see, they’re quite old, and the copyright has expired.
Kodak Monograph 1: The silver bromide grain of photographic emulsions, Adrian Peter Herman Trivelli (1921)
Kodak Monograph 2: The theory of development, Adolph H. Nietz (1922)
The Photographic Negative, William Henry Burbank (1888)
Written as a practical guide to the preparation of sensitive surfaces by the calotype, albumen, collodion, and gelatin processes, on glass and paper, with supplementary chapters on development, etc.
Photographic printing methods: a practical guide to the professional and amateur worker, William Henry Burbank (1891) (thanks, Glenn!)
Via APUG member Emulsion
Security holes in Photoshop CS2 & CS3, fixes available
Adobe says:
Critical vulnerabilities have been identified in Photoshop CS2 and CS3 that could allow an attacker who successfully exploits these potential vulnerabilities to take control of the affected system. A malicious BMP, DIB, RLE, or PNG must be opened in Photoshop by the user for an attacker to exploit these potential vulnerabilities. Users are recommended to update their installations with the patches provided below, and Adobe encourages all customers to be cautious before opening any unknown file, regardless of which application they may be using.
Software fixes for both Mac and Windows available from Adobe’s security bulletin, Photoshop CS2 and CS3 updates to address security vulnerabilities.
Lens manufacturing videos
Also check out Canon’s lens manufacturing video. It’s worth watching both as they use different processes.
Holga focus test
Squarefrog, who has put together what I believe to now be the definitive Holga resource site, has done a focus test to see if the generally cites distances for each focussing icon are correct.
He writes:
I decided to dispell some Holga focus myths and actually test the focus distance for the 3 people, and 7 people (group) settings. My camera was put on a tripod and the focus fixed in the middle of each setting. Then I moved the tripod back 2 ft after each picture. All pictures were taken using the cloudy setting with the aperture mod, so the aperture was about f/10…
See the results in a photo set on Flickr.
Adventures in year-old DIY C-41 chemistry
See what happens when alspix—the man who brought us the now-legendary matchbox pinhole camera—processes film in year-old, over-used C-41 colour negative chemistry from a DIY kit. The results are surprising!
Read about it at Alspix Stuff.
He used this Nova C-41 kit, which is available in the UK. For those in the US, check out the variable time, variable temperature Arista quart and gallon C-41 kits, as well as pint, quart, and gallon E-6 (slide/positive/reversal) kits from Freestyle Photo.
Holga exposure mystery not solved
The exposure math of the Holga has always been a mystery to me, because it seems to violate the reliable Sunny 16 Rule. The rule basically states that if you set your shutter speed to the ISO of your film and the aperture to f/16, you’ll get a solid exposure in direct sunlight. (For example, if you had ISO 50 film, you’d set your shutter speed to the nearest number, likely 1/60.)
Admittedly, every Holga is a bit different, but I did have one of my Holgas tested with a shutter speed tester, and it came in at a fairly reliable 1/100 sec, which is what it’s supposed to be. As I found out while I measured for The facts about Holga apertures, a stock Holga has an aperture of f/13.3, regardless of the position of the sunny/cloudy switch. So with aperture of roughly f/13 and a shutter speed of 1/100, you should be able to shoot ISO 100 film in bright sunlight and have a proper exposure. (Technically about a half stop over as we’re at f/13.3 instead of 16, but that’s well within the exposure latitude of modern print films, so you should just get a little extra shadow detail).
So why the hell do I have to shoot ISO 200 or 400 film in bright sunlight to get a decent exposure, while I get underexposed mud with ISO 100, which should work perfectly? After thinking about it for a while, I strongly suspected that the plastic "Optical Lens" must have a good deal of transmission loss and was blocking two stops of light, so I set up a test: I pointed a Canon 580EX flash fitted with a Sto-Fen Omni-Bounce diffuser straight into a Holga with a Sekonic L-558R meter (which is extremely accurate and consistent) stuck in the back. I metered the flash through the camera five times with and five times without the lens in place and was fucking shocked by what I discovered: there was effectively no transmission loss. The readings averaged out to differ by only about 1/6 of a stop.
WTF??!? It’s not the lens. It’s not the aperture. It’s probably not the shutter: while I can allow for the possibility that the speed changes over time—it was over a year ago I had it tested—I consistently have the same exposure requirements with all of the 8-ish Holgas I have. What’s left? Light-eating gnomes?
Ultra-thin folded lens
Someone figured out how to fold a 35mm effictive focal length lens into 5mm!
Here’s the abstract of the paper Ultrathin cameras using annular folded optics, by Eric J. Tremblay, Ronald A. Stack, Rick L. Morrison, and Joseph E. Ford, from the Feb 2007 issue of Applied Optics:
We present a reflective multiple-fold approach to visible imaging for high-resolution, large aperture cameras of significantly reduced thickness. This approach allows for reduced bulk and weight compared with large high-quality camera systems and improved resolution and light collection compared with miniature conventional cameras. An analysis of the properties of multiple-fold imagers is presented along with the design, fabrication, and testing of an eightfold prototype camera. This demonstration camera has a 35 mm effective focal length, 0.7 NA, and 27 mm effective aperture folded into a 5 mm total thickness.
Unfortunatey the complete paper costs US $22 for non-OSA members, but I suspect that it’s pretty unreadable by people without advanced optical systems design training anyway. Check out this summary article at PhysOrg instead, which makes sense to the rest of us.
Mitsubishi Electric develop deblurring flutter shutter camera
Following this month’s 33rd Annual Siggraph Conference in Boston, MA, a research team at Mitsubishi Electric is catching the attention of camera manufacturers for their photo motion deblurring technology, called a flutter shutter camera.
The flutter shutter camera is a modified camera that can capture moving objects at an exposure time of over 50 milliseconds, like high speed motion cameras. Using a coded exposure sequence, the new flutter shutter camera could recover text from a speeding car and sharpen images, according to the researchers.
Introduced in early August, three Mitsubishi Electric researchers presented the abstract, "Coded Exposure Photography: Motion Deblurring using Fluttered Shutter" at the largest computer and graphics conference, Siggraph. After one year of research development, Mitsubishi Electric Research Lab (MERL) senior researcher Ramesh Raskar, MERL visiting researcher Amit Agrawal, and Northwestern University computer science assistant professor Jack Tumblin launched the new prototype with the goal of deblurring photos.
Continue reading this article at DigitalCameraInfo.com or read the paper at Mitsubishi.
The sample photos are nothing short of jaw-dropping. This combined with Ren Ng‘s plenoptic camera that allows post-exposure refocussing [see previous post] would be a truly amazing thing.