Use of X-ray film: technical discussion with example images

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Originally Posted by senderoaburrido

I understand what you are saying. The thing is that the filter I chose is cyan (discovered it as a "minus-red" filter), which should be blocking the majority of the red light coming through to the spot meter. Regardless of my source of light, the meter ought to be giving me readings that are consistently parallel with the specific sensitivities of the film, no? I figured this would allow me to establish a baseline ASA/ISO.

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I cannot advise on your scenario.

Why not try it both ways? This stuff is cheap. I cut to 4x5 and run through a bit finding my way through the smoke.

That's an interesting statement. I thought every photographer knew ortho films speed changes with sun angle and latitude. Yes, the film is faster at the 50th latitude then at the 45th latitude. Sun angle is directly connected with the amount of red in the light, ortho film is insensitive to red, so the redder the light, the slower the film at that time.

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Originally Posted by Randy Moe

I think most now believe ISO on this film changes by angle of Sun. I see people choosing 50, 80, 100. I shoot it 'now' at 50 under studio strobes. Which is working for me in studio.

But most advice here on ASA is find your personal EI.

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How would I go about establishing a fixed number by experimentation? Do I set different ISO's on my meter, then take pictures, and compare the results against my little gray card by eye?

EI calibration is a big topic, and it depends on how much you want to delve into the Zone System. Here's a good place to start on the LFP site:

http://www.largeformatphotography.in...-meter-cal.pdf

I highly suggest reading Ansel Adams' "The Negative" back-to-front as well. But the extremely watered-down version is yes, set a few different ISOs on your meter (a.k.a., bracket) on the same photo and find out what EI works best for your setup.

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Originally Posted by Corran

But the extremely watered-down version is yes, set a few different ISOs on your meter (a.k.a., bracket) on the same photo and find out what EI works best for your setup.

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"Expose for the shadows, develop for the highlights" is the rule to remember when judging your test exposures.

Or expose for the mid-tones, develop for the shadows and agitate for the highlights - see Minor White.

Perhaps this sun angle thing is why I don't find BTZS to be accurate for x-ray film. My cold light probably puts out more blue light in testing while the sunlight here has more red.

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Originally Posted by j.e.simmons

My cold light probably puts out more blue light in testing while the sunlight here has more red.

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It's that influence that I'm trying to eliminate by leaving the minus-red filter on my spot meter. No more red-variance corrupting the readings and making all this guesswork necessary.

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Originally Posted by Michael E

"Expose for the shadows, develop for the highlights" is the rule to remember when judging your test exposures.

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no its not. Its only when you follow certain school.

Sorry, got dragged away by work things.. :)

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Question of correct exposure is vast and outside of the scope of Xray imho.

In general Randy is totally right. Experimentation is key to get things to your liking. Not to someone else's liking. To yours. Xray is fairly forgiving and cheap, so why not just go and play with it.

I don't know what certain school that would be. But for the Ortho film school (X-ray film is one) it is a very good process to start with. With Pan film, it is much more difficult to do.

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Originally Posted by SergeiR

no its not. Its only when you follow certain school.

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