Printable View
On a lark I did a double-exposure onto a sheet of 8x10 Fuji HR-U from 2 similar (but slightly offset) half-35mm negatives during my last printing session. Tossed the sheet into a flat bottomed tray of stale xtol for 15-20 minutes with irregular agitation. Not exactly crisp, but it's another reminder to me of why I like experimenting with xray.
Attachment 211396
Can you share details regarding exposure?Quote:
Originally Posted by lanactoor
I tried to make inter-positive, its hard to determine correct exposure to enlarge and make positive image.
I don't have a timer so I just flicked the switch powering my enlarger quickly. 60W incandescent light source through a 50mm lens. Not sure of the f number used.Quote:
Originally Posted by Bucky
The enlarger head was quite far from the baseboard as this was a half-frame 35mm -> 8x10 enlargement. If your problem is overexposure even at minimum aperture, you can use a longer focal length lens to move the enlarger head higher or use a lower wattage bulb. Focusing becomes more difficult, but once the light reaching the film is faint enough exposure times will align more closely with paper and you can use more familiar printing techniques for determining exposure.
Edit: If you really want accuracy you'll need not only a timer but also some sort of metering system or at least a measurement of the intensity of light reaching the film at a given enlargement configuration. Weird ortho film curves and reciprocity aside, there are many such discussions wrt devices such as the Ilford EM10 on the net.
As a suggestion you can use an incident light meter as in this video at 4:52.Quote:
Originally Posted by lanactoor
https://youtu.be/4aNysC-X8T0?t=292
Timer good
Test strips ARE necessary
I chose Fuji HR-U Green (which is both green and blue sensitive) because it seemed like the "normal" one that people were using for photography, and am getting some pretty normal looking images from it. It is grainy compared to normal film but oh so cheap. You could always use a filter to block green light but I think you won't. My test showed it to be ISO 80 under high-CRI LED light. Under warmer light, it will be slower because it is not sensitive to red.
I think your choice of a pyro developer is a good one. I also chose a pyro developer (510 Pyro) for cost reasons, but for UV contact printing processes with x-ray film, they make sense for other reasons:
- Yellow staining of denser areas increases effective contrast with regard to UV light while having less effect on traditional photo paper / scanning. This means you can still scan and traditionally print your alt process negatives.
- Tanning hardens the emulsions, making these obnoxiously delicate films easier to work with (after developing)
Compared to standard film, the Fuji Green HR-U development times are very fast. I imagine this is to facilitate developing quickly by machine in the doctor's office. What has been working for me with 510 pyro is 1:250 dilution for 9 - 11 minutes in vertical stainless tanks on Kodak hangers.
I have found that working with this film is terribly sensitive technique. It has been a long process getting to an 8x10 negative without obvious flaws. Here are some notes from my journey:
- After messing around with a bunch of bare bulb red LEDs to use as safe lights (none were safe), I finally did the obvious thing and bought an old safe light from a dentist's office off ebay. They are not expensive and they work fine. The correct safelight filter for HR-U is GBX-2, which is a dark dim red. You can find a Kodak recommended bulb wattage and distance on the interenet. Since the film is so delicate, I can't see ever being able to work with it in the dark. For example, you can't slide it around on surfaces without scratching it.
- I started by cutting the film down to 4x5. It's faster / cheaper / easier to do your testing at this size and it turns out there's a bunch to be learned just by cutting the film. I tried a few paper cutters and ended up choosing the inexpensive Dahle 18e Vantage which has a soft rubber foot that comes down to hold the film while it is being cut. The foot is soft enough that it does not scratch the film and lifts entirely out of the way so you can carefully place the film rather than sliding it around. Since the bed is metal, I have been using a plastic triangle held down with magnets as a backstop to make precise repeatable cuts. Mine came slightly out of square but I was able to adjust the top rail with a screwdriver.
- HR-U has branding at the edges (something about safety film) and curved corners. I can't see having these artifacts in my contact prints so I have been cutting down larger film. I trim the edges off 14x17 sheets and then cut two 8x10s and three 4x5s from each sheet. I don't think there's any meaningful cost savings to be had from this but it is flexible and removes the rounded corners and branding.
- It's easy to scratch the film while cutting it, loading it into film holders, and onto hangers. I now wear clean rubber gloves and slot the film in as close to its final position is possible rather than sliding it around. By minimizing touching and movement I have mostly been able to eliminate scratches, though still get the occasional surprise.
- Since the emulsion is on both sides, anywhere that touches the emulsion during development will be slightly underdeveloped. The Carr film hangers have a thick top bar with a wire clip on it. The top bar covers more than just the margin of the film. On normal film it would be resting against the non-emulsion side and wouldn't be an issue but for double-sided film, it is touching emulsion and creates a slightly lighter strip and can scratch that area as well. I also noticed a ghosting from the clip. I think the Kodak hangers are better for this film.
- It is important not to mix hanger types. The hangers are designed to contact each other and not the film, but if you mix them you will get scratches on the back side of the film where the adjacent hanger touches it during development.
- At 8x10, I found my 4x5 agitation technique produced surge marks where the pores in the Kodak hangers let fluid pass. The pores are only on one side of the hangers (again designed for single-sided film). My fix for this was to avoid crowding the tanks and to move /very/ slowly for the agitations. My current developing process is a 4 min pre-soak, dip and dunk for the first minute (alternating lift directions), one dip and dunk for each additional minute. The lifting and dunking movements are on the order of 10 seconds each, such that the first minute only has 3 dip-dunks over 60s.
Excellent post. Thank you for your effort.
Yes, experimenting can be rather surprising. This was one of my early, if not first attempt at using Xray film. I had use a split dark-slide with 8X10 to make 2 4X10 images on a sheet, and when I processed the film I was quite disappointed at how under exposed the negatives were, so I didn't even bother finishing the wash, just threw it in the trash. Next morning I happened to glance at it and could barely make out the image, so for the heck of it I washed it and hung it to dry - scanned the next day.Quote:
Originally Posted by lanactoor
https://www.dropbox.com/s/dtla6ky4fq...griib.jpg?dl=1
While agitating very slowly did work to reduce the surge marks from the pores in the film holders (maybe 85%) what is working even better is more agitation.
Today I tested the same "Kodak style" dip-and-dunk movement as before (lift and tip 45 deg, replace; lift and tip the other way 45 degrees and replace) but instead of a ponderous 20s dip-and-dunk, I did it in about 10 (twice as fast). Furthermore, instead of a single dip-and-dunk every minute, I did two dip-and-dunks every 30s (4x the volume).
The surge marks are now 98% gone. I can see some faint unevenness that corresponds to the pores in the sides of the film holders by scanning and making extreme adjustments to the image but the problem with surge marks coming from the bottom of the negative is completely gone. I'm not sure how it's possible to get sideways surge marks. Maybe I tipped the negatives too much during the dip-and-dunk movement.
Quote:
Originally Posted by sabeluc
Yes variation in agitation is important to find your process
I use a Calumet Gas Burst tank system bought well used bit by bit
Got a lot of flack from some members and some still insist I am all wrong
I have shown it here on LFPF many times