Setting personal film speed on LF; can you use 4x5 and apply to 8x10?

Kino

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Assuming you are using the same film brand/speed B&W film and developer combination, would there be any problems testing out a film in a smaller size to establish an effective film speed and then using it on a larger format?

For instance, my whole plate camera has holders that can be adapted from 3.25 x 4.25, 4x5 and 5x7 in addition to whole plate.

If I chose a film brand/speed that is available several of these sizes and use the same processing method with the same developer, can I test out at 4x5 and extrapolate throughout the entire range for that camera?

Would it be reasonably accurate to move laterally these results to another camera, say a 4x5 monorail with entirely different optics?

Seems it should work at least in the one camera, but might need a bit of fudging for moving over to another camera and same film/dev combo.
 

Focomatter

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Yes you can for the most part. Be aware that the same film name might be used for different emulsions. For example Kodak has recycled the Tri-X name many times as well as the difference between the pro version and regular version. I think you will be standing on firmer ice if you see a data sheet where it states explicitly that the emulsion in question is packaged in XYZ and that these X, Y, and Zs correspond to your desired film sizes. Also compare films of the same age - same expiration year would be a good idea.
 

juan

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That's what I did, but as Focomatter says, be sure the film is the same. Of course moving to a different camera may mean introducing differences - particularly shutter speed. But you have to make adjustments for that anyway.
 

koraks

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Focomatter said:
Be aware that the same film name might be used for different emulsions.
Click to expand...

Yes, but I'm personally not aware of any film that has a different emulsion across sheet film formats. So 4x5 is generally the same stuff as 8x10, just cut to a smaller size.

The main source of doubt I'd have (and it's really just a small sidenote) is that agitation can be different across formats, depending on how the film is being processed. This could result in small differences in gamma. Personally, I would (and in fact do) happily ignore this, in part because I generally process 4x5 and 8x10 in the same way, and in part because I expect the difference to be marginal at best.
 
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Kino

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Ah, yes; thanks for reminding me to pay attention to expiration dates and batch numbers!
 
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Kino

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juan said:
That's what I did, but as Focomatter says, be sure the film is the same. Of course moving to a different camera may mean introducing differences - particularly shutter speed. But you have to make adjustments for that anyway.
Click to expand...
 
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Kino

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I have finally managed to obtain a pair of Jobo Expert drums that will work from 4x5 up to 8x10 for my ATL 2200 and plan to use this system to test.

It was quite a fortunate day I was able to get this machine 20 years ago for scrap value; but I just hope the electronics last as long as I do!
 

ic-racer

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I found measurable differences in development activity from, say an 8" strip of 35mm film in a 1500 series drum, compared to eight 35mm films in the largest 1500 series drum or a single sheet of 4x5 in a drum vs ten 4x5 sheets in a drum, all with the same mathematical concentration of developer per square inch.

So, depending on the size of film on which one makes the step wedge exposure, and how it is processed, and how the speed information is retrieved from the step wedge exposure, there could be significant differences in speed calculation between film sizes of the same emulsion.

Since I retrieve speed information using the "W-Speed" calculation, which is not affected by development, I DO use 35mm strips of HP5 to predict the speed of 8x10 HP5.

You can use "Delta-X" also, but I found the math to calculate the delta value too complex for the spreadsheet software available to me. "W-speed" is based on inertia (but it is NOT inertia), which is the x-intercept, which is easy to find with my spreadsheet software.
 

Doremus Scudder

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The largest variable will be your meter. If you use the same meter and metering techniques for both sizes, that will get you in the ballpark.

Other variables are shutters (hopefully, you've had them tested and know they are accurate or how much to compensate) and development techniques. If those are close too, then you should be able to get usable data.

That said, if you're looking for a personal E.I. for Zone System use, you can probably just save yourself the trouble and start by rating your film 2/3 stop slower than ISO speed (that's the difference between ISO and Zone System metering placement). Then just keep careful field notes and adjust as necessary. I've never had a film that needed more than 2/3-stop adjustment for my ZS work. The ones I'm using now I'm rating at either 2/3 or 1/3 stop slower than ISO speed.

Best,

Doremus
 

pentaxuser

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In terms of a settíng a personal fílm speed from a box speed why would the format be important? If, say, Ilford rates HP5+ at 400 for all HP5+ formats then why does the size of the film matter?

From some answers it sounds as if it might for different formats but I cannot work out why this should be.

pentaxuser
 

DREW WILEY

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Doing rotary drum development could introduce a complication if it's a multi-sheet drum and the agitation pattern somehow shifts with different film sizes, or if the developer volume is somewhat different. And you haven't stated your specific developer choice yet - not all of them are ideal the rotary route.
 
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Kino

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I plan on starting with either D76 Stock or D-23; haven't made up my mind.

As for volume, I will use the stated volumes in the Jobo manual for expert drum B&W developers.



Upon reflection, I probably won't push the results to smaller sheet film, as I will be developing that with another system.

I really do not plan on processing sacrificial sheets to maintain a full load each time, as I am not the caliber of John Sexton or Ansel Adams.
 
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MattKing

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Different film formats employ different forms of anti-halation and use different film substrates. The camera systems also tend to add different amounts of flare.
While those factors may not affect ISO speed ratings for film - they tend to be adjusted for by the manufacturers - they can affect personal EI ratings for individual photographers.
A personal speed rating is also usually intended to factor in the photographer's preferences, and those preferences may vary with the format.
 

DREW WILEY

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Ha, Kino - you'd be surprised just how often AA's negs were unevenly processed, and what kind of printing headaches that caused. Don't be intimidated by the reputations of those before us. They didn't do things perfectly either. But you do need to be patient and work through any of your own potential bellyflops. Experimentation is the name of the game. Start with your best shot. You'll improve with experience. But for me, tray processing of sheet film proved to be much simpler.

Sacrificial sheets do nothing worthwhile in a drum. But sufficient fluid volume does count. Sometimes you need more volume in the drum simply to keep the flow pattern consistent or prevent undue oxidation of the developer. Rotary processing is pretty aggressive, especially since Jobo units run at a somewhat higher RPM than I would prefer, even at the lower settings.

What you will probably discover is that D76 STOCK solution is probably too strong and fast-acting for rotary work. 1:1 makes more sense, especially if using it one shot. You also have to keep in mind, if you don't already know it, that D76 either needs to be standardized fresh, just mixed, or after a week or so - time needed to allow the developer to pH stabilize. It shifts.
 
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Kino

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Drew,
Thanks for all the tips. It's all in the learning game.
 
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