Help me interpert my film developing test results

[williaty]

I am trying to confirm that I am giving my negatives proper development before I start changing things around to get my summer and winter developing results to match. However, given the long developing time, I'm suspicious of the fact that my results seem to indicate needing more developing.

I am working the 4x5 Ilford HP5+ rated at ISO 250. I placed a 10-stop, 21-step Stouffer step wedge on the film. I took the camera outside, pointed it at a white door, and defocused massively. I used a reflective spot meter to determine the Zone 10 exposure for the door. I exposed the film at the Z10 exposure. I developed in XTOL 1:1 at 68F for 12 minutes in a Jobo on rotation setting P. Once washed and dried, I measured the density using an X-Rite 810 set to the Visual channel. There are two potential problems with this procedure:

1) The 810 will not read the little bit of Filmbase+Fog under the "wings" of the film holder as the strip is too narrow. I was able to get what I think is a Fb+F reading by reading a place on the bottom of the neg where something shadowed it.

2) Due to the aforementioned something shadowing the bottom of the neg, I lost steps 21 and 20 and it looks like Step 20 should have been my Z0 step. This gives a 1/2-stop guess about where the speedpoint actually was.

My results:


Filmbase+Fog: 0.14
Zone X: 1.93 over FbF
Zone V: .98 over FbF
Zone V.5: 1.06 over FbF

Looking at those numbers, I am under-developing the film, correct? In The Negative the appendix on Film Testing Procedures says the Z5 value should be 1.15 to 1.25 above FbF for condenser enlargers and 1.25 to 1.35 above FbF for diffusion enlargers. I'll be printing on a diffusion enlarger once I get it set up but the scanner acts more like a condenser enlarger. If you take into account the fact that the shadow at the bottom of the neg gives me a 1/2-Zone uncertainty in where Z1 was, both .98 and 1.06 (my measured values on Z5 and Z5.5) are below even the condenser numbers.

I would like to bump up my developing temperature about 5F because I can't get the water down to 68F in summer. Is that small temperature change alone likely to get the values up where I need them?

Did I make any other mistakes?

[chassis]

Wow very impressive! I can't answer your questions but appreciate your commitment to rigor, and looking forward to smarter minds than mine chiming in. Keep up the good work!

[Michael R]

A few comments:

1. 1.15-1.35 above FB+fog is for Zone VIII exposure, not Zone V

2. Test methodology needs to be revisited because the bottom of the curve looks very strange. There should be some compression in the lowest exposure densities, but your curve shows the opposite (ie your curve has its highest contrast in the Zone I-II range).

3. A few things to watch out for when doing an in-camera test: (i) Watch out which direction you defocus in because that can impact exposure. The best way to do this would be to focus the lens at infinity (focus on something far away, then run the test). (ii) Watch out for lens falloff, especially at large apertures since this can lead to different parts of the wedge getting different amounts of exposure.

[williaty]

1. 1.15-1.35 above FB+fog is for Zone VIII exposure, not Zone V

Doh!

Well, if Z8 is supposed to be in that range, then my Z8 is 1.51 to 1.62 above FbF and I'm actually already hot on development!

Given how muddy the images look, if they're already too contrasty in the negative, then I dislike HP5+ even more than I thought. Bring back my beloved Plus-X!

Regardless, another test sheet will be going in to the tank the next time I run a tank that has room for an extra sheet.

2. Test methodology needs to be revisited because the curve looks very strange in the low Zones. There should be some compression in the lowest exposure densities, but your curve shows the opposite (ie highest contrast in the Zone I-II range).

If you ignore the Z1 0.14 value that is due to the shadow, then Z1.5 on up is linear-ish, which yes is weird but isn't as weird as extra separation on toe.

[rob4x5]

Have you compared your curve with Ilford's published curve for HP5+?

[williaty]

Have you compared your curve with Ilford's published curve for HP5+?

I wasn't aware their was one. Ilford's HP5+ datasheet doesn't have one.

[rob4x5]

Interesting, because some of their films do. Did you check their website?

[williaty]

Interesting, because some of their films do. Did you check their website?

Yes.

[Alan9940]

I just happen to be in the middle of some film testing myself--mostly because it has been about 35 years since I originally did all this testing and because materials have changed over all those years--so I offer the following for your consideration:

1. Use a sheet of unexposed, but processed following your normal procedures for reading Zone 0. As you said, the narrow bit of unexposed film is much too thin; unless your densitometer aperture is 1mm which I don't recommend. I use a 3mm aperture.

2. For Zone 1 exposure, focus your camera on infinity and point it at a smooth black surface in shade on a cloudless day. I use a piece of black matboard. Doing your Zone 1 exposures this way simulates the very dark things you'll be reading out there in the 'wild.'

3. I don't know why you're using Zone X as the basis for your highlight density because that Zone is too far up on the shoulder of the curve to be useful. Your highlight should be based on Zone VIII and should read in the range of 1.25 - 1.35 density (over fb+f) for diffusion head printing on grade 2 paper or with a #2 VC filter. FWIW, I tend to favor the higher end of that range because I know my printing paper of choice will handle it.

Regarding the film speed test, I've found that the least error prone way to expose the film is to set my meter for 1/4 box speed, expose, close aperture 1/2 stop, expose, and continue stopping down a 1/2 stop until my exposure is double box speed. Logarithmically, this isn't the most accurate, but it's close enough to extrapolate the correct Zone 1 exposure.

Sorry, I know nothing of using step wedges for this type of testing, but I hope something I've said here helps.

[stawastawa]

Alan and Michael mention some important points.

For measuring zone 0, another option is to put a piece of of black tape over part of the negative - this give you a little patch to measure zone 0.

Another thing to look out for is flare, and give you are shooting a white door, that might be what is boosting your shadow values.

As to evaluating the results - it looks like you have a useable distribution of tones. place your exposure to match the recorded zone 3 and 10 and you will have some good linearity to work with.
sorry to not have more specific advice at the moment. good luck!