4x5 tests extended to 8x10 - OK or not?

[splanken]

I have spent time doing tests with sheet film using a densitometer (which is for sale by the way) and am happy with my speed and dev times for trix and FP4 4x5. I have 2 questions...
1) can I happily use these times and speeds for 8x10? I shot my first 4 tri-x 8x10 with the same speeds/times and they were really flat... Did I screw up or do I need to go through the entire testing procedures again with 8x10 (which to be honest I can't afford the time to do). Is there a common conversin factor that I am un-aware of?
2) I came up with a speed for TRI-X of 160, and a speed for FP-4 100. These speeds seem to be common for a lot of folks. Why do we all get these speeds when Ilford an Kodak get different ones??

Cheers all ya' all.

Simon:

[Gene McCluney]

You should be able to transfer your results from 4x5 to 8x10 of the same film types and emulsions. The only variables would be your lenses and shutters which can vary from lens to lens. Some people prefer 8x10 negatives to be a bit denser (for contact printing) than 4x5 but that is personal preference. Your speeds for Tri-x and FP-4 sound like what a lot of people use.

If you use the same lens and shutter on 8x10 that you are using for 4x5, and you develop in exactly the same manner (tube, tray, tank) as 4x5, your densitometry results should be the same.

[Ken Lee]

"Why do we all get these speeds when Ilford an Kodak get different ones??"

Recently, there have been threads on this forum dedicated to that question.

In a nutshell, different people mean different things by "speed", and while films don't vary much from batch to batch, our technique and equipment differ from one another.

Some people follow a method based mainly on densitometry. Some people follow a method based mainly on darkroom printing. Some use a method which combines both. Some don't use any method at all, and just wing it.

If we are getting superb and repeatable results, and our numbers are fairly close to what others are getting, we're probably in good shape, and should move on to other considerations.

[Walter Calahan]

Why, personal choice, water conditions, different methods of agitation, etc.

I'd test a few sheets of 8x10 in comparison to your 4x5 to confirm that they are the same.

[mcfactor]

Do you use exactly the same development method for both formats?

[ic-racer]

I'll agree with others in that since you are probably using a different lens/shutter for the 8x10, your 'in camera' film speed test may not be the same as the one you did for 4x5.

And, in terms of development, there are many variables. Same size tank or tray or proportionally bigger tank or tray? Same amount of developer per square inch of film? Same developer volume per square inch of film?

In terms of re-doing tests, you are half way there. If the negatives are flat, increase development buy 20 percent for the next sheet. If you shadows don't have enough density decrease you exposure index a little.

I pretty much use the sensitometer and densitometer to see where I am after using trial-and-error to establish an exposure/development combination that prints the way I like.

[Brian Ellis]

Different water alone can make a surprisingly big difference in development times. When I attended John Sexton's workshop at Anderson Ranch (Aspen), we were told to increase or reduce (I forget which) our usual development times by 20% or so based on the Workshop's experience with many students over the years, apparently because of the difference in the water there and the water at most people's home town.

[C. D. Keth]

The difference between your EI and the factory EI is just the difference between lab and real working conditions. They are testing the film speed with a standard developer and development method that will give a certain middle-grey density for a zone 5 exposure.

You are testing for the film speed with your developer and your development method that gives a printable negative for your system and preferences. Given all those differences, it's kind of surprising that your EI is only a third of a stop different from theirs.

[PATRICK GAINER]

Depth of field can be a problem if you don't watch out. If you use the same lens on both cameras, the depth will be constant with f-stop. To keep the same hyperfocal distance with lenses of different focal lengths one must keep the aperture diameter constant, so don't expect to get the same depth of field with a 12 inch lens at f/64 that you would get with a 6 inch lens at f/64. Your tests at f/32 on the 4x5 will more likely correspond with results at f/64 on the 8x10.

[Bjorn Nilsson]

The difference between your EI and the factory EI is just the difference between lab and real working conditions. They are testing the film speed with a standard developer and development method that will give a certain middle-grey density for a zone 5 exposure.
...

Let me knitpick just a little. :) Any EI (both factory and personal) is (and have always been) established by finding how much exposure is needed for 0.10 above base+fog with that film/developer combo.
Developing time is another matter, which affects the EI (which in other words is zone I) very little, but the rest of the zones more and more, depending on the time choosen. E.g. with TriX in D76, the EI can be at 200 when developing for 6½ minutes, EI 250 when souped for 8 minutes and say EI 320 when cooked for 11 minutes. (There is much more difference at zone V, not to mention zone VIII.) So, the EI doesn't change that much, but the gamma (i.e. the angle of the straight path of the curve) does. And it's this gamma value which is interesting when establishing the developing time.


//Björn

[Ken Lee]

Björn, that was a delightfully articulate and clear explanation. Thank you !

Since we are already nit-picking, let me pick a nit, and suggest an explanation of that curious expression. :)

According to Wikipedia (http://en.wikipedia.org/wiki/Nitpicking)...

"Nitpicking is the act of removing nits (the eggs of lice, generally head lice) from the host's hair. As the nits are cemented to individual hairs with louse saliva, they cannot be removed with lice combs and, before modern chemical methods were invented, the only options were to shave all the host's hair or to pick them free one by one."

[Bjorn Nilsson]

Well, I didn't know that...
But I know that I'm half-bald though. :)

//Björn

[Chuck P.]

I have spent time doing tests with sheet film using a densitometer (which is for sale by the way) and am happy with my speed and dev times for trix and FP4 4x5. I have 2 questions...
1) can I happily use these times and speeds for 8x10? I shot my first 4 tri-x 8x10 with the same speeds/times and they were really flat... Did I screw up or do I need to go through the entire testing procedures again with 8x10 (which to be honest I can't afford the time to do). Is there a common conversin factor that I am un-aware of?
2) I came up with a speed for TRI-X of 160, and a speed for FP-4 100. These speeds seem to be common for a lot of folks. Why do we all get these speeds when Ilford an Kodak get different ones??

Cheers all ya' all.

Simon:

I assume tray development is what you are doing, you didn't mention. I develop 4x5 in a combi-plan tank and I get very good results, agitation is very consistent. If you are developing 4x5 in a daylight tank and then switch to tray development with the 8x10---game over, you have to redo the tests.

If you are tray developing the 4x5, then I was wandering if agitating an 8x10 sheet is different than for a 4x5 sheet. By different I mean is it slower than for 4x5--this could make a significant difference in the results. In which case, testing would need to be redone to account for variance in agitation----just a thought, IDK.

[Bruce Barlow]

Go make pictures. If you don't like something, change it. Too flat? Develop more. Poor shadow density? Slower EI. Et cetera.

Life's too short to spend testing. They tore down my favorite barn a month ago, and burned the farmhouse as a fire-fighting exercise last weekend. Many fine pictures disappeared that I only had nine years to make, and didn't. I think the supermarket that will replace these beautiful buildings will be much less interesting to photograph.

[HBDesert]

I had the same problem. I did my tests using 400 TMAX on 4x5 film. My target process is PD/PT and I use a Jobo processor for my film. My other film size is 12x20. Not wanting to blow through a bunch of 12x20 film I short cut my tests by exposing 2 sheets. I processed one at my "normal" time that I use for 10 sheets of 4x5 and another at 20% longer. I found that the 20% longer neg fell almost exactly in line with my "normal" 4x5 neg while the "normal" time used for my 4x5s did not produce the values in the dense areas I was looking for. Subsequent negs have proved the 20% longer processing time to be almost perfectly in line with 4x5 negs.

Take Care,

Doug