XRAY Film As A Copy Film?

[Craig]

Why would X Ray film have emulsion on both sides? Shouldn't single side work fine for X Rays?

 

[Alan Townsend]

People who have used most xray films would get this. It's got nothing to do with DOF. This is double-sided film. It has emulsion on both sides. The side facing the lens during the exposure is sharp. The emulsion on the other side is unsharp. There is no way around this unless you strip the unsharp side after processing... But this technique literally cuts the density range in half. I tested this 'til the cows came home. An easier way around this issue, is to use single-sided xray...

I would think removing the back side emulsion before exposing the film would work much better than after since this would also greatly reduce the halation. This could be done just using fixer after masking the front. Or, the back side could be turned black by appropriate agent to act as anti halation later, then removed after processing. That would make it hard to judge density while developing. However, since the max density of hru xray film is around 3.5 (what I measured on hru 2 years ago), a single side would give only 1.75, which is close to what I get with my "bad film".

 

[koraks]

Why would X Ray film have emulsion on both sides? Shouldn't single side work fine for X Rays?

First, keep in mind x-ray film doesn't really record x-rays. It can And it would, but in a typical medical setting the flux is way too small to generate an image. Instead, the x-rays hit a phosphor screen which emits visible light, and that is what creates the image.

As to the double sided nature: I suspect it's because it's basically "free" additional density for the same number of photons and thus the same x-ray dose. Which means less exposure to the patient for the same image density, do less risk of tissue/dna damage. Ease of use might also have something to do with it as there's no risk of loading the film in the wrong orientation in the exposure unit.

Apparently applications like mammography require higher resolving power or better/higher fidelity rendering of very fine structures. For this purpose a single-sided film is apparently preferable because it can better deal with scatter, halation etc. which would erode this fine detail.

 

[Alan Townsend]

I watched your video this AM. Contact printing xray to xray doesn't work great as you found, but reversal processing would also be difficult for several reasons. Two years ago, I found that using a piece of ortho litho film along with a piece of xray can work together fairly well. The ortho litho raises the contrast enough to get good dmax on the xray without using print developer, and the xray negative can be as sharp as one done in camera. The ortho litho should be the interpostive, then the xray internegative. I was also contact printing xray onto ortho litho in 4x5 with topside down, then enlarging the ortho litho onto xray. Doesn't work as well, but kindof OK.

 

[Alan Townsend]

As to the double sided nature: I suspect it's because it's basically "free" additional density for the same number of photons and thus the same x-ray dose. Which means less exposure to the patient for the same image density, do less risk of tissue/dna damage. Ease of use might also have something to do with it as there's no risk of loading the film in the wrong orientation in the exposure unit.

My understanding is that in the xray film packs, there are phosphor screens on both sides of the film acting somewhat independently, but for the same reasons you mention, to reduce patient xray exposue. Also read that if a single exposure on xray film is correct, the patient is exposed to less xrays than with the newer digital systems.

 

[mshchem]

I would like to see a video showing stripping one side. The ammonia (aqueous solution) never dawned on me. You're literally removing the gelatin, correct?

Could you do this after processing? Or are you doing this after processing?

Reminds me of the old wizards of graphic arts a bit.

 

[koraks]

The ammonia (aqueous solution) never dawned on me. You're literally removing the gelatin, correct?

Yeah, that's correct - and yes, ammonia is always dilute when used in a household! Otherwise we'd choke on it as it's a gas; many people don't seem to realize...
Btw, regular household bleach also works (Chlorox etc.) I bet sodium hydroxide would work as well, esp. if you give it some time.
Basically whatever breaks the protein bonds in the hardened gel.

I tried the stripping thing once or twice but disliked it; yes, if the sheet is carefully taped down, the bottom side remains protected. You're still left with an unstripped edge at that point. And it takes just a small seam and some of the ammonia, chlorox etc. finds its way underneath the sheet and capillary action guarantees a swift destruction of a large part of the image.

Contact printing xray to xray doesn't work great as you found

I imagine, yes. Ah well, just set up the enlarger to do 1:1...
Btw, I have reversal processed x-ray film; it's not very difficult. It takes some dialing in of the right exposure, but that's also true for a workflow with an interpositive.

 

[Alan Townsend]

I imagine, yes. Ah well, just set up the enlarger to do 1:1...

That's what I was planning on doing, although I would use my press camera with an enlarging lens at 1:1 to make the copy in daylight. That halation maybe only slightly more this way, but then again might be double, which is not good.

Btw, I have reversal processed x-ray film; it's not very difficult. It takes some dialing in of the right exposure, but that's also true for a workflow with an interpositive.

Making a reversal processed internegative with the correct density range would be challenging. Just making one in the ballpark, not so much. With the double sided film, the back side is one of the problms. I would use a blue filter or perhaps just a piece of clear xray film scrap to attempt to get equal exposure on both sides. Otherwise, the lack of exposure on the back side would result in a very dense reversal processed result. The film would need to be flashed with a controlled exposure to reduce the density range, which would also change with development times. It can be done trial and error, but would eat lots of film. Zone system in the darkroom would help lots. Measure density range and max highlight transmission to determine exposure and processing time and then find flash exposure in the table that would need to be generated to repeat reliably. Would need characteristic curves for several developing times.

 

[koraks]

I see what you mean about the backside going black. That's indeed a disadvantage when trying to do this with reversal processing on double-sided film.

 

[Alan Townsend]

I see what you mean about the backside going black. That's indeed a disadvantage when trying to do this with reversal processing on double-sided film.

One possible way around it is to do the flash exposure through the back side. The emulsion that develops due to the flash exposure gets eaten away by the bleach so does not contribute to the final density. I think this can be done, but would take some work to make work well.

 

[koraks]

That's actually a nice workaround, although it demands a fairly controlled setup for the flash exposure.

Ah well...I never really warmed up to the double-sided film and as time goes by, it seems I can only find more reasons for it...

 

[mshchem]

I tested it quite a bit. As long as the film is duct taped down to glass, the side facing the glass is safe (that's the side we want to keep). I never had an issue with bleed over. Very little ammonia is required to remove the emulsion.

Are you stripping after processing?

 

[Andrew O'Neill]

Are you stripping after processing?

Nope. Removing the unsharp side does improve sharpness, but it also cuts the density range directly in half, making it unusable for the Alt. processes that I use.

 

[Alan Townsend]

Nope. Removing the unsharp side does improve sharpness, but it also cuts the density range directly in half, making it unusable for the Alt. processes that I use.

After watching your copying video again a few times, and looking at the HRU film curves both from their brochure and your earlier video where you chart them, I'm pretty sure HRU is a good fit for reversal processing enlarged negatives with density ranges near 1.8 from small camera negatives with density ranges from about 1.0 to about 1.6 using print developer and a good blue filter. A little flashing on the back side may help control density ranges using a yellow or orange filter to try to limit it to the back side. This would also work from 4x5 hru negative with fairly low contrast, which I've found works best for this film, or at least is much more linear when processed for low density ranges around 1.0-1.3. These would be easily proofed cyanotype, then enlarged to higher density ranges for VanDyke, Ferroblend, or whatever. The question is when optically copying an HRU to an HRU does the halation multiply like it did in your contact prints or does it just add together a bit? I believe the fuzziness in your copies is caused by multiple halations from both films as well as the unsharp mask effect of the two planes on each film. The halation is mostly in the near field of the film, so is removed by the enlarging lens into the far field.

Thanks again for all the great videos.

 

[Andrew O'Neill]

After watching your copying video again a few times, and looking at the HRU film curves both from their brochure and your earlier video where you chart them, I'm pretty sure HRU is a good fit for reversal processing enlarged negatives with density ranges near 1.8 from small camera negatives with density ranges from about 1.0 to about 1.6 using print developer and a good blue filter. A little flashing on the back side may help control density ranges using a yellow or orange filter to try to limit it to the back side. This would also work from 4x5 hru negative with fairly low contrast, which I've found works best for this film, or at least is much more linear when processed for low density ranges around 1.0-1.3. These would be easily proofed cyanotype, then enlarged to higher density ranges for VanDyke, Ferroblend, or whatever. The question is when optically copying an HRU to an HRU does the halation multiply like it did in your contact prints or does it just add together a bit? I believe the fuzziness in your copies is caused by multiple halations from both films as well as the unsharp mask effect of the two planes on each film. The halation is mostly in the near field of the film, so is removed by the enlarging lens into the far field.

Thanks again for all the great videos.

Thanks for your input, Alan. It's greatly appreciated!

 

[mshchem]

Nope. Removing the unsharp side does improve sharpness, but it also cuts the density range directly in half, making it unusable for the Alt. processes that I use.

If I wanted to use X-ray film to make conventional contact prints on ordinary Ilford Multigrade paper, could I improve the sharpness by after removing the "unsharp side" After the film was processed??

I have always been reluctant to fool around with X-ray film because of the double emulsion. I need to get some X-ray film to play with.

 

[Andrew O'Neill]

If I wanted to use X-ray film to make conventional contact prints on ordinary Ilford Multigrade paper, could I improve the sharpness by after removing the "unsharp side" After the film was processed??

I have always been reluctant to fool around with X-ray film because of the double emulsion. I need to get some X-ray film to play with.

Yes, you can. I did it years ago. It's easy to strip the unsharp side. The nice thing about xray film is the price.

 

[mshchem]

Yes, you can. I did it years ago. It's easy to strip the unsharp side. The nice thing about xray film is the price.

Thanks for the information. Enjoy your Hasselblad too!