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holmburgers
07-26-2010, 02:11 PM
Howdy everyone,

I've been intrigued lately by one-shot cameras; you know, the ones that took 3 separation negatives at once. It's hard to find any good resources online, does anybody have some links or something?

I'd like to see the high end models, as well as more consumer oriented ones (though I doubt many consumers used them).

Cheers

holmburgers
07-26-2010, 02:19 PM
Ok, apparently these were some top manufacturers.... Jos-Pe, Bermpohl, Klein and Mirkut.

It's funny how after you post, you start to find stuff....

http://www.nationalmediamuseum.org.uk/autochrome/pdfs/A%20Short%20History%20of%20Colour%20Photography%20-%20Part3.pdf

And hmmm, wonder if this guy is still up for sale....
http://photo.net/large-format-photography-forum/003A2g

And check out this beauty... eBay item #180535914853

Jeff Searust
07-26-2010, 02:57 PM
Get Sandy King's book on Carbro off the Alternative Photography site. I think it is really the place to start, since you can always use a camera with filters and film rather than a dedicated color camera to take the multiple images. Start simple....LOL.

I have also been thinking of using a sliding back arrangement on an 8x10 to do 4 4x5 images, and just hold the filters in front of the lens by hand as I expose for each color. Then cut those up and do carbro tissues from that. ---

Many ways to do this without having the fancy camera from day one.

holmburgers
07-26-2010, 05:05 PM
Actually, you've beat me to the punch! I was thinking about carbro/tri-color-carbon, but I'm not honestly considering that at the moment whatsoever. (still cutting my teeth on black & white)

Really I'm just interested in seeing the designs and reading about them. Were there any that didn't use filters, but instead reflectors? I'm reading Friedman's 'History of Color Photography' and he says there are mirrors that will selectively reflect only certain colors (primaries) with 90% efficiency. With this in mind, I'm surprised they used filters at all. But who knows how practical/affordable this other system would have been.

Jeff, do you do your own color carbro? I'd really like to know more about it and its modern day feasibility. Shoot me a PM if you're interested.

Dan Fromm
07-26-2010, 06:16 PM
http://www.galerie-photo.info/forumgp/read.php?2,30010

Y'all shouldn't be so US-centric.

holmburgers
07-27-2010, 11:19 AM
I blame the United States educational system for this.... it seems there's only language here.... AMERICAN! :P

Dan Fromm
07-27-2010, 07:08 PM
I see from y'r profile that you were hatched after foreign language requirements had, for the most part, gone away. More child abuse, IMO.

holmburgers
07-28-2010, 11:44 AM
I concur. Two things that are educational system needs.... the metric system & foreign language requirements.

flatulent1
07-28-2010, 12:11 PM
That's only one thing; the metric system is a foreign language. :p

holmburgers
07-28-2010, 12:21 PM
haha!

I'd argue that what we use is more of a foreign language. It doesn't make any f-ing sense! What, how many ounces in a pound?, wait, how many fl. ounces in a quart?, doh, how many pints to a gallon?!?! AAGHHGGH

Please, give me multiples of 10 or give me death

;)

michaelbsc
07-28-2010, 01:46 PM
Howdy everyone,

I've been intrigued lately by one-shot cameras; you know, the ones that took 3 separation negatives at once. It's hard to find any good resources online, does anybody have some links or something?

I'd like to see the high end models, as well as more consumer oriented ones (though I doubt many consumers used them).

Cheers

I've been toying with the mechanics of trying to build one, and it's not trivial. Getting a Phillips prism that will work is the hard part to do a professional job of it. I have yet to locate an old '60s TV camera to cannibalize. Modern Phillips prisms are minuscule.

However, searching prisms unsuccessfully at Edmund Scientific I did hit on the idea of trying to do it subtractively rather than additively. This way you only need two images.

You can easily get a plate beam splitter that's fairly large to split the incident beam. The transmitted beam will be reduced by slightly more than one f-stop, and the reflected beam will be approximately the same but oriented improperly because of the reflection. You'd need a front surface mirror to reverse the orientation of the reflected beam.

Several email exchanges with the Edmund Optical support team agreed that the beam splitter shouldn't affect the optical quality of the image produced by the lens in either the transmitted or reflected image. So long as the light paths are equal you'll get two images focused on the targets, each with slightly less than half the light of the original incident beam. (There is some loss in the beam splitter, but not a lot if it's professional quality optical gear.)

Plus you'd need the proper filters to make your negatives carry the right information.

And finally the reproduced color rendition isn't spectacular, just pretty good. This is why Technicolor's three color system blew away the two color systems that preceded it. Three color additive is capable of rendering true colors across the spectrum. Two color is a trick to get us to perceive missing colors that works because of how our eye/brain system is constructed.

Making a two color system at home isn't isn't trivial either, or I'd be all over it. But it isn't outside the realm of hobbyist possibilities either. And a plate beam splitter and front surface mirror is a lot less expensive than getting the tri-color prism.

Of course, you could always take three images with filters, but that's not what the thread is about.

holmburgers
07-28-2010, 02:25 PM
Wow, indeed that is quite the undertaking. The necessary precision boggles the mind, especially with a 3 color set up.

I wasn't familiar with the Philips Prism, by name at least. This is interesting... http://www.alt-vision.com/color_prisms_tech_data.htm

So I admit that I'm not up on the "latest" in tri-color separation (*cough *cough, when would that have been, 1951? ;)) but what about reflectors that can selectively reflect colors? Mirrors were coated by means of sputter deposition techniques to produce only reflections of given wavelenghts. This would eliminate the need for filters.

In the book mentioned in my OP this was discussed, but he introduced it more as the "standard" by which all other systems will be judged, saying that this is theoretically possible. So IDK about logistics.

Another question; do the separation filters all possess the same filter factor, and if not, how does one match exposures? ND? Only a consideration with a one-shot obvioulsy.

pgomena
07-28-2010, 04:33 PM
The red filter tends to pass a bit more light than the others. I seem to remember the need to sandwich a bit of cyan filtration with the red to balance out the transmission, in effect creating a bit of neutral density. I think it was about 1/3 stop. You'll need better research than my memory, however.

Peter Gomena

michaelbsc
07-29-2010, 11:17 PM
Here's little more information than I had the other night. Not much mind you.

http://www.widescreenmuseum.com/oldcolor/additive-subtractive.htm

Look down near the very bottom of the page above for the two-color subtractive information. This is the page that got me thinking about using a plate beam splitter and a front surface mirror. It is boatloads easier than finding or fabricating a Phillips prism.

I did toy with the idea that you could just use several beam splitters to get your three images, but that's a lot of loss in the system. Basically you'd loose at minimum 2 stops if they system is perfect. And the beam splitters farther down the chain have to get pretty big or you have to stick with small negatives. When I said earlier that a plate beam splitter was affordable I didn't mean 8x10! The Phillips prism avoids those losses.

Another link for two color:

http://www.widescreenmuseum.com/oldcolor/subtract.htm

Sorry there's no hard core data here. I guess we have to rediscover it and make it up for ourselves.

holmburgers
07-30-2010, 12:37 PM
Michael, kudos for the links; very cool.

You know, it's almost more interesting to see a 2-color approach because afterall, we're so used to seeing beautiful, 3-color reproductions that nearly mimick reality. It's more interesting/profound to see something that's slightly different from reality. I'm on your 2-color bandwagon!

Hey, check out this book (http://books.google.com/books?id=ac2n_9kFqB0C&pg=PA508&lpg=PA508&dq=friedman+history+of+color+photo&source=bl&ots=LcOoKPv4c_&sig=9ErLjdqVjOk_LYKx6fGlj0-NFe4&hl=en&ei=4P5STM_wK-rsnQf98KWLAw&sa=X&oi=book_result&ct=result&resnum=1&ved=0CBYQ6AEwAA#v=onepage&q&f=false) and go to Chapter 5. It's the Friedman book I've been alluding to. He basically outlines all approaches that have been taken for color-separation cameras.

You're sure to find some new, novel idea that perhaps hadn't occured to you before and might make your task easier. It's what I would describe as "very thorough".

As for the two-color requirements, are you still searching for the appropriate filters to do it? I'm sure this information is in some book somewhere, I'll try to do some searching.

2F/2F
07-30-2010, 12:59 PM
The big benefit of the one shot camera is that things do not have to be still to photograph them and get a "normal" picture. If you do three separate exposures, any movement between shots will result in some pretty psychedelic effects where the movement occurred.

BetterSense
07-30-2010, 01:25 PM
I did toy with the idea that you could just use several beam splitters to get your three images,
If you are talking about partially-silvered mirrors, I'm not sure if it would work as well as you hope. Usually optical mirrors are silvered on the front surface, so that the light isn't refracted twice from traveling through the glass on the front of a conventional mirror. If you used a partially silvered mirror, the light that bounced off the front would go one way, and that that went through the mirror would go another way.

This might be fine depending on what your criteria are for alignment. It seems to me that if I were doing it, I would just give up on trying to get the 3 negatives exposed so the images were perfectly aligned when you stacked them up for printing. You would need a lot of precision to do that. But if you can resign yourself to visually lining up the negatives on a light box, then your camera just has to have the same magnification between the 3 negatives, and they can be misaligned by quite a bit (whole mm) without it being a problem.

michaelbsc
07-30-2010, 03:53 PM
If you are talking about partially-silvered mirrors, I'm not sure if it would work as well as you hope. .... But if you can resign yourself to visually lining up the negatives on a light box, then your camera just has to have the same magnification between the 3 negatives, and they can be misaligned by quite a bit (whole mm) without it being a problem.

I don't see that image alignment is terribly hard. Tedious for certain, and it would probably take a while to get it right. But I don't see it as intrinsically hard.

As for magnification, if you're shooting all three negatives through the same lens simultaneously, then this cannot be a problem unless you have some other lensing elements in one of the paths. After all, if you've got the image focused on three GGs at the same place, then all three signal paths must necessarily be the same, hence the magnification must be the same.

The biggest problem with using beam splitters to get three color separation in my mind is loss of light in the process. Each pass will give you a one stop decrease, and then the filter factors have to come into play. Even if you start at f/11, you're going to wind up doing no better than f/32 by the time you get to the film plane. And maybe even worse if you've got to introduce a bunch of neutral density in some filters to get them all to match. (OK, Ok, to the purist it isn't really smaller diameter f-stops, but signal attenuation along the transmission pathway. But when calculating exposure I, and probably most of us, think in f-stops.)

The Phillips prism is the Cadillac method to do the separation, but so far I haven't found any unused Phillips prisms laying around in my junk stash. If anybody has a spare one let me know!!

(I even thought of cutting up a bunch of acrylic sheets and making a Phillips prism out of water chambers, but I don't know enough about the physics of light to figure out the dimensions based on the differences between glass and acrylic/water. I know it's different, but I don't know how to correct for it.)

Hence my searches for the two color method. There's far less attenuation in the signal path with only a single split. So what if you do two-color and it isn't true color; sometimes you gotta compromise. It is just a hobby, after all.

And I did track down the filter colors at one point, but I've lost that info.

MB

2F/2F
07-30-2010, 04:05 PM
If contacting a user of these cameras "back in the day" is of any interest to you, Richard C. Miller is still alive, here in Los Angeles, at age 98 (http://www.richardcmiller.com/).

His film holders (5x7) had built-in filters. (I know this because I have seen them in person.)

He used a National Lerochrome camera like this one (a measly 3x4, though it is very neat that it is a tungsten model): http://www.collectiblecameras.com/product.php?productid=169958&cat=350&page=1. It is now owned by his assistant.

holmburgers
08-03-2010, 11:41 AM
That Lerochrome model is a beauty!

As for equalizing exposures on the film end, it'd be interesting to experiment with different film speeds for each color. This introduces problems with contrast though, but perhaps a system of development could be worked out to minimize the effects. But as I understand it, keeping the same contrast is pretty crucial for accurate color, for obvious reasons.