SP-445 agitation test results challenging

[Ulophot]

Thanks, esearing. I keep Photoflo out of the tank, putting washed negs in a tray of it instead. My normal development is 9 minutes. I may try your long presoak; I have used a 1-minute one, which appeared to make no difference. Otherwise, I'll continue to experiment with agitation schemes. Tim, the 445 inventor, has been responsive and helpful as always; I'll just have to keep at it.

[Nodda Duma]

My test targets have been, variously, a large sheet of matte white card stock taped to my flat outside house wall under overcast conditions; two sheets of letter-sized copier paper taped next to each other on a flat surface and illuminated with bounced light; an area of rich blue sky. No variation across the field in any direction read by my spot meter in any of these cases.

I have tested with one sheet or two in the tank, both with emulsion toward the tank center, i.e., film loaded on inner side of holder(s) when holder(s) inserted; and with emulsion toward the outer tank walls from the outer sides.

The image shown, scanned from a contact print, approx. Grade 2 ½, is the best result I have managed to achieve after a half-dozen tests, still showing the mottling. The dark center line is a small space between two sheets of paper on my upright piano board, photographed out of focus.

The last time I recall having to struggle to get even agitation was back in the days of 35mm Tech Pan and Technidol (some of you surely remember that joy), which required a very quick ¾-inversion flip of the tank with no rotation a couple of times every 30 seconds.

Any ideas?

As an optical engineer who has tested non-uniformity of imaging systems many times over my career, my first and primary suspect is the actual setup of the test described: I.e. Sheets of regular paper are demonstrably non-uniform, and scanning / digitizing a uniform scene like this introduces its own non-uniformity. Testing for uniformity in the way described leads to suspect results.

If you want to clean that up, start with metering / exposing on a clear sky and also taking a digital image of the exact same area to correct for non-uniformity in the scene. I'd shoot a second sheet of film back-to-back and develop to the same times / temps using your Jobo or tray or whatever you know provides uniform results.
Another approach to better results is to significantly defocus your camera, but you'll need a much larger target: A large piece of foam board would be more uniform than printer paper. Additionally, include a black board target somewhere in the scene to use as a check to ensure you are using correct development times and scanning correctly.

You mention deviating from the techniques in their video. I have no doubts that Tim exhaustively tested agitation before settling on the best method to present in that video. It's probably worthwhile to follow the development steps exactly as a control for further experiments.


Hope this helps,
Jason

[Ulophot]

Thanks, Jason. I did shoot a couple of the sky and did defocus the white targets. I subsequently developed sheets from the same series in my Jobo rotary tank, and although there was some extra density at edges I didn't expect, possibly due to developing only a single sheet in a technically adequate but less-than-full volume of developer, I did not get the mottle I have been getting in the 445. I think I just need to try a few more adjustments to my agitation routine. Again, the problem is not overt in my photos, and I have done lot of tests using the 445 ( for exposure, N+ and - developments, etc.) with various test targets and not seen significant problems most of the time.

[Ulophot]

After a number of further tests and back & forth with Tim at Stearman, I have succeeded in getting even development in the sheets that face the tank walls, and nearly even development of those facing in. In the latter, I still find signs of unwanted turbulence on the long edge closest to the baffles, where the fluids enter. The uneven density shows up in a contact sheet of a an evenly illuminated “gray card” target; it probably would be negligible in most of my images.

I may get around to testing the slow sideways tilts mentioned above, but I expect that my overall density will decrease, forcing a change in all my development times, just as agitation every 30 seconds increases the density by the better part of a stop. (I use 10 seconds on the minute, comprising 4-5 full rotations).

For those who may experience challenges with the SP-445, I share my recent lessons:

1. Tim’s demonstrated agitation technique (https://www.youtube.com/watch?v=Uojra1s1HrI) works better, for me at least, than the hand-over-hand rotation I had been using. The momentarily discontinuous motion seems to help. The reversal of direction also appears to be important for even development.

2. The developer will tend to surge through the slots in the empty holder and leave clear evidence on the sheet facing it. If using only one holder, either remove the other or load processed discard film into the other holder.

I’ll post back here if I solve the turbulence issue.

[wattsie]

I mostly develop TMax400 and HP5+ in dilute Perceptol (normally 1+3) and so my develop times are on the longer side (16 mins or so). I pre-soak the TMax, but not the HP5+ as Ilford (I believe) specifically say no pre-soak. I use minimal agitation - constant for the first minute, twice every minute for the following 6 minutes and then twice every 2 minutes until the end. I have found that agitation needs to be very gentle to avoid turbulence on the edges. However, with such gentle agitation I am getting even development across the negatives.

[Certain Exposures]

As an optical engineer who has tested non-uniformity of imaging systems many times over my career, my first and primary suspect is the actual setup of the test described: I.e. Sheets of regular paper are demonstrably non-uniform, and scanning / digitizing a uniform scene like this introduces its own non-uniformity. Testing for uniformity in the way described leads to suspect results.

If you want to clean that up, start with metering / exposing on a clear sky and also taking a digital image of the exact same area to correct for non-uniformity in the scene. I'd shoot a second sheet of film back-to-back and develop to the same times / temps using your Jobo or tray or whatever you know provides uniform results.
Another approach to better results is to significantly defocus your camera, but you'll need a much larger target: A large piece of foam board would be more uniform than printer paper. Additionally, include a black board target somewhere in the scene to use as a check to ensure you are using correct development times and scanning correctly.

You mention deviating from the techniques in their video. I have no doubts that Tim exhaustively tested agitation before settling on the best method to present in that video. It's probably worthwhile to follow the development steps exactly as a control for further experiments.


Hope this helps,
Jason

What system do you use to develop your 4x5 negatives and positives?

[GuillaumeZuili]

I really like these tanks. I hold 2 of them to process 8 sheets. Contrary to my roll processing tanks for these I go for a strong agitation. I had some issue on my first try and found out the key was a strong agitation.
No pre-soak. 30sec the first minute and after that 10sec per minute.
Using DK50 1+1 and D23 1+1
Many hundreds sheets processed since without any problem.