Film area size

TareqPhoto · Sep 25, 2014

Hi again,

Not sure if i titled this thread correctly, but if not then please correct it for me if possible.

I want to know how do you determine the area of the film format?

For example, what is the area of the 35mm roll of film? Also with 120 format film roll, and also with 4x5/5x7/8x10 sheets.

I would like to know so it may help me for chemical volume usage.

Let's say, 10x 35mm rolls of film equivalent to how many sheets?

Bill Burk · Sep 25, 2014

The chemical volume required for film is often calculated by imagining what will fit on an 8x10 inch contact print.

A 36 exposure roll of 35mm
A roll of 120 film
Four sheets of 4x5 film
One sheet of 8x10 film

It makes calculation easy to use those equivalents.

paul_c5x4 · Sep 25, 2014

A rule of thumb that I use:

36exp 35mm equals one roll of 120 or four sheets of 5x4 film.

Based on that assumption, if (for example) Kodak state that the capacity of one litre of D76 is ten rolls of film, I know I can develop 40 sheets 0f 5x4.

MattKing · Sep 25, 2014

One 36 exposure roll of 135 film = one roll of 120 film = four 4x5 sheets = two and a bit 5x7 sheets = one 8x10 sheet = 80 square inches.

The Kodak data sheets have this information in the film development section - although I don't know if there are many references to 5x7.

TareqPhoto · Sep 25, 2014

Cool, so quick straight forward answers, i really appreciate that, so now i can make my decisions about film and chemicals to use at what volume, so i don't need to waste things as chemicals or film or money buying those.

So if one developer saying that it's 1L is processing approx. 8 rolls of 35mm film, it means i can process approx. 32 sheets of 4x5, but then should i use 30 sheets just in case that it may not be really enough for 32 sheets completely?

And if we say that i will use 30 sheets, and the processor can accommodate up to 6 sheets at once, means i should divide the sheets into 5 groups or times so each time i process 6 sheets?

And i am thinking about processing color films, and i don't know how long the chemicals last since i open and use them, because then i have to process at once before the chemicals exhaust quickly even before i can process half of its volume.

cliveh · Sep 25, 2014

TareqPhoto said:
Hi again,

Not sure if i titled this thread correctly, but if not then please correct it for me if possible.

I want to know how do you determine the area of the film format?

For example, what is the area of the 35mm roll of film? Also with 120 format film roll, and also with 4x5/5x7/8x10 sheets.

I would like to know so it may help me for chemical volume usage.

Let's say, 10x 35mm rolls of film equivalent to how many sheets?

You don't need to know the area of roll film as it usually tells you the chemical volume needed on the bottom of the tank.

MattKing · Sep 25, 2014

cliveh said:
You don't need to know the area of roll film as it usually tells you the chemical volume needed on the bottom of the tank.

The bottom of the tank only tells you how much liquid is required to cover the film and reels. That amount may not be the right amount to use, because the chemistry involved may require more in order to have enough activity to do its job correctly.

Or alternatively, that minimum volume may be wasteful of chemistry, in that it may use more than would otherwise be necessary - inviting consideration of more dilute mixtures.

The volumes listed on the bottom of the tanks are a practical minimum, and the capacity of the maximum capacity of the tank is a practical maximum, but neither measurement is ideal.

Terry Christian · Sep 25, 2014

TareqPhoto said:
And i am thinking about processing color films, and i don't know how long the chemicals last since i open and use them, because then i have to process at once before the chemicals exhaust quickly even before i can process half of its volume.

I've found that a good benchmark for the shelf life of working strength C-41 developer is about six weeks, if stored in a normal plastic Datatainer bottle. In glass or in less porous containers, it may last quite a bit longer. Bleach and fixer will last for at least months. I've had bleach and fixer that I mixed in the fall still work perfectly when used in the spring after having sat idle all winter.

For B&W developers, like D-76, plan on six months' life in a plastic Datatainer bottle.

Vaughn · Sep 25, 2014

You could probably stretch it out to 32 sheets of 4x5. But better to err on the side of caution dealing with future negatives!

If it is a one-shot processor (like drums), work out how many ml (or oz) of developer a single sheet of 4x5 sheet needs and make sure at least that amount is in the processor per sheet, be it two sheets or 6. Toss when done.

or...if the liter (for example) of developer is in a tank and one runs several batches of 4 to 6 negatives each, you will have to adjust your development time by about +10% for every four sheets of 4x5 run thru the chemicals. This is because the developer is weakened slightly every time a set of 4x5's are run through.

Kodak TMax in straight D-76 I remember it being sixteen 4x5 sheets to a quart.

TareqPhoto · Sep 25, 2014

I am not worry about B&W developer or processing, i only worry about colors processing, be it C-41 or E-6, so i don't want to miss with that the first time i hope to use in the future when ordering color chemicals and processor.

Storage is another story and i asked about it long time ago, maybe i will re-open it for color processing if necessary, but for now i will read about chemicals life time and then calculate how many films i will process before i lose the chemicals in a period of time.

Steven Lee · Nov 25, 2023

MattKing said:
One 36 exposure roll of 135 film = one roll of 120 film = four 4x5 sheets = two and a bit 5x7 sheets = one 8x10 sheet = 80 square inches.

The Kodak data sheets have this information in the film development section - although I don't know if there are many references to 5x7.

Sorry to be resurrecting the old thread, but I believe it contains incorrect advice. According to Z-131 one 4x5 sheet equals 0.4 rolls of 35m. That's quite far from 0.25 rolls as you stated. You have to rely on chemical capacity tables in datasheets because a geometric comparison is not straightforward due to varying % of film area getting exposure. Smaller formats are less efficient due to borders occupying larger % of their area.

Vaughn · Nov 25, 2023

But one still develops, fixes and washes the borders/rebate along with the image area.

Steven Lee · Nov 25, 2023

@Vaughn Unexposed borders do not exhaust a developer, and with a fixer the opposite is true. That is precisely why I am sending people to reach for a datasheet, not a ruler.

Vaughn · Nov 25, 2023

But it is not significant. The amount of exposure (including the relative amounts of shadows, mid-tones and high lights) will make that difference insignificant to 99% of film users.

Rick A · Nov 25, 2023

I find it easier to go by what Kodak printed in the Data Guides than nit-pick exact dimensions. I learnt this over 60 years ago, it's always worked and see no need to change.

MattKing · Nov 25, 2023

Steven Lee said:
Sorry to be resurrecting the old thread, but I believe it contains incorrect advice. According to Z-131 one 4x5 sheet equals 0.4 rolls of 35m. That's quite far from 0.25 rolls as you stated. You have to rely on chemical capacity tables in datasheets because a geometric comparison is not straightforward due to varying % of film area getting exposure. Smaller formats are less efficient due to borders occupying larger % of their area.

The equivalencies were, of course, quoted from Kodak's black and white datasheets.
For colour, Z-131 gives you much finer detail than "one 4x5 sheet equals 0.4 rolls of 35mm":

It even tells you how much to adjust for sprocket holes!

As I read it, a 135 - 36 with tongue removed is 0.05145 sq. meters after accounting for the sprocket holes.
A 4x5 sheet is 0.01290 sq meters.
According to Z-131, the area of a 4x5 sheet is 25.1% of the area of a 135-36 with tongue removed.
Z-131 has a bunch of other relevant information affecting replenishment and other realities of commercial processing like carryover in roller transport processors. I expect it is those influences that change the comparative factor from 25% to 40%.

Steven Lee · Nov 25, 2023

The key table is "Chemical capacity" which states that one 4x5 sheet requires as much C41 developer as 0.4 rolls of 35m. What matters is chemistry volumes, not square inches. Anyway, now I feel we've covered this and the thread can go back to hibernation for another 7 years

MattKing · Nov 25, 2023

Steven Lee said:
The key table is "Chemical capacity" which states that one 4x5 sheet requires as much C41 developer as 0.4 rolls of 35m. What matters is chemistry volumes, not square inches. Anyway, now I feel we've covered this and the thread can go back to hibernation for another 7 years

As that table 3.3 gives different numbers for different films, it is even more clear that there are other factors besides area to be taken into account:

Steven Lee · Nov 25, 2023

Actually my point was that geometric area is unreliable indicator for the required chemistry volume. @Vaughn see above. The difference in area to chemistry volume ratios is exactly why area efficiency matters. Unexposed borders and leaders add up! 4x5 is far more efficient with its area than 35mm roll film.

TLDR: don't bother with geometric area, look at datasheets for chemistry volume requirements.

Dustin McAmera · Nov 25, 2023

I think it is just area, but as you said before, you need to discount the edges of the 135 roll that don't consume developer because they aren't exposed.

If we suppose
* the roll film is 36 frames, each 36x24 mm and with an unexposed 2mm gap between each frame and the next;
* the perforations are 5mm along each edge, of which about half is the actual perforation hole: but they are so little exposed we may neglect the edge except at the leader.
* the length of film developed includes say 10 cm of leader, of which 5 cm is exposed. This does include exposed edges.
* the length of film developed includes 5 cm of tail, but this is completely unexposed.
Then the total area of the film, including that of the perforations, leader and tail, is
( no. of frames * (36mm of frame + 2mm of gap) + leader + tail ) * 35mm of width
A = ( 36 * ( .036 + .002) + .1 + .05 ) * .035 = .05313 square metre.
Of this, the area actually demanding anything of the developer is
( no. of frames * (frame length x height) + ( 50mm of leader * (frame height + 2 * 2.5mm for exposed edges)))
B = ( 36 + ( .036 * 024 ) + ( .05 * ( .024 + 2 * .0025) ) ) = .032554 square metre

For the sheet, suppose it is exactly 4 x 5 inches, and that 2 mm along each edge is unexposed because of the film holder.
Then its total area is C = 4 * 5 * 0.0254^2 = 0.0129032 square metre
And its exposed area is D = ( 4 * .0254 -.002 ) * ( 5 * .0254 - .002 ) = 0.01245 square metre

So by total area, the roll area is A/C = 4.11 times that of the sheet (or the sheet is 0.24 rolls)
But by exposed area it is B/D = 2.61 times that of the sheet (or a sheet is 0.38 rolls)

I know I could have extracted official values for some of my assumptions from the area table, but this does well enough to show that the unexposed edges make a big difference. There's no quarrel between area and capacity.

Vaughn · Nov 26, 2023

Steven Lee said:
Actually my point was that geometric area is unreliable indicator for the required chemistry volume. @Vaughn see above. The difference in area to chemistry volume ratios is exactly why area efficiency matters. Unexposed borders and leaders add up! 4x5 is far more efficient with its area than 35mm roll film.

TLDR: don't bother with geometric area, look at datasheets for chemistry volume requirements.

And my point is that in real use, going either way does not matter. Too many other factors (type of film, distribution of lights/darks on the neg, etc. Just be consistent and judge by the results.

Doremus Scudder · Nov 26, 2023

Overexposed film and high-key photographs use more developer. Underexposed film and low-key photographs use less. Blank frames use none. Light struck film uses a lot.

The point being, the variation in exposure and subject luminances make a lot more difference than rebates. Assumably, the worst-case combination scenarios of these factors were taken into consideration by manufacturers when determining capacities for their developers. This, of course, along with a safety factor to make sure there was a bit of buffer just in case. The result? Published developer capacities are likely generously underestimated for average use. No real need to worry about not having enough developer if you follow any set of guidelines: developer needed for a given area of film or the data sheets recommendations. Even if you exceed capacity by a tiny bit things are likely to come out well.

Doremus

Steven Lee · Nov 26, 2023

Vaughn said:
And my point is that in real use, going either way does not matter. Too many other factors (type of film, distribution of lights/darks on the neg, etc. Just be consistent and judge by the results.

Of course it matters. If one is led by "it does not matter" advice on the Internet, he's risking under-developing his negatives by diluting a developer too much on the very first run, especially in a rotary processor. I believe I've seen a few instances of that happening here. That is why datasheets exist: they give you a safe starting point, and the nearly 2x error I spotted above matters a great deal.

Obviously not reading documentation and learning by doing is also a valid way to live. But people who subscribe to that philosophy probably wouldn't be asking about chemical capacity here.

Vaughn · Nov 26, 2023

Steven Lee said:
Of course it matters...

Does not matter because the difference is insignificant. See Doremus' post above.

Edit...if people use the amount to develop an 8x10 to determine the amount of developer for a 35mm roll of 36...they will be using 'too' much and not run any risk of having their developer exhaust under normal conditions.

Steven Lee · Nov 26, 2023

@Vaughn Not your call. What is insignificant for one is unusable trash for another. Suggesting to ignore manufacturer's recommendations is a net negative contribution to any photography thread.

Film area size

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