Conversion from rolls of 35mm to 4x5

[Jim Cole]

What factor do you use to convert a developer's minimum requirements to develop a roll of 35mm film to equivalent 4x5 sheets?

My math says a roll of 35 equals about 2 1/2 sheets of 4x5.

Is there an accepted conversion?

Thanks,
Jim

 

[Ian Grant]

1 roll 35mm - 1roll 120 - 4 sheets 5x5 - 1 sheet 10x8 thats the basic rule of thumb

Think a contact sheet for a roll of 35mm is 10x8 then it's more logical

Ian

 

[Shawn Dougherty]

Jim,
Ian's right on... save a typo.

1 (36 exposure) roll of 35mm = 1 roll of 120 = 4 sheets of 4x5 = 1 sheet of 8x10.

 

[Jim Cole]

Thanks folks. I still can't reconcile the numbers, but I'll accept the consensus.

Now I can get some developing done!

 

[BradS]

as was already pointed out, if you try to make a contact sheet of an entire roll of 35mm, it takes up about an 8x10 sheet of paper. Similarly, you can make a contact print of four sheets of 4x5 on that same 8x10 sheet of paper...so, roughly speaking, 1 roll of 35mm has about the same area as four sheets of 4x5 or one sheet of 8x10.

 

[Jim Cole]

Brad,

Makes sense I guess. I was using the estimated surface area of a roll of 35mm 36 exp based on the size of a frame and some leader to determine the conversion and came out with the lower ratio.

The film came out fine yesterday using the 1:4 number and saved me a lot of developer.

Thanks again everyone.

 

[Chazzy]

Thanks folks. I still can't reconcile the numbers, but I'll accept the consensus.

Now I can get some developing done!

Think of printing proof sheets. One roll of 35mm, one roll of 120, 4 sheets of 4x5, and one sheet of 8x10 all fit on one page. Does that help explain why they're the same in area?

 

[David A. Goldfarb]

Makes sense I guess. I was using the estimated surface area of a roll of 35mm 36 exp based on the size of a frame and some leader to determine the conversion and came out with the lower ratio.

You're leaving out the film edges and spaces between the frames, which are also coated with emulsion of course.

 

[Jim Cole]

Think of printing proof sheets. One roll of 35mm, one roll of 120, 4 sheets of 4x5, and one sheet of 8x10 all fit on one page. Does that help explain why they're the same in area?

Chazzy,

Exactly what Brad said previously, and it does make sense and now it will be easlier to remember. However, if you think about it, there is a lot of white space on an 8x10 proof sheet of 35mm images...nah...I won't go there.

David,

You're absolutely correct. I thought I added enough extra to compensate in my calculations, but evidently there is more non-image area than I thought. Guess I'd have to open an old 35mm cassette and measure the darn thing, but then I'd have to account for the sprocket holes!

Anyway, 1:4 works and thanks again to all who contributed.

 

[gainer]

There is actually a lot of black space on a 35 mm proof sheet. Any way, it's a rule of thumb for estimating developer capacity. One person's thumb may be larger than another's, and anyway, how do you account for different exposures, stuck shutters, or any of several other ways the required developer capacity may be greater or less than estimated? You don't. You have to figure the worst case will be if everything is nearly black. 1:4 is close enough for government work.

 

[alanrockwood]

A 35mm frame is 1.5 inches long. It is about 1 inch wide, depending on exactly how you do the measurement. Therefore, figure about 1+1/2 square inches per 35mm frame. Multiply by about 40 (36 frames plus a length of leader, rounded off to a convenient number), and you get 60 square inches. That's about 3/4 the area of an 8x10 sheet or four 4x5 sheets, which rounds off to be roughly equivalent in area for the formats.

Actually, the active area 35mm might be slightly smaller than 1+1/2 inches, but likewise a 4x5 is actually smaller than its nominal 4x5 dimensions, so it roughly averages out to equivalent area. Also, the leader is probably not four frames long, but on the other hand it is developed to a much higher density, so it also roughly averages out.

However, in the end a 35mm roll might have slightly less effective area than four 4x5 sheets, so if you are striving for the nth degree of accuracy there might be a slight non-equivalence, with a 35mm roll being slightly smaller than four 4x5 sheets, but probably not to the degree that you calculated.

 

[alanrockwood]

Jim,

Following up some more, I can see where you get your number (24mmx36mm actual picture area, converted to square inches, multiplied by 36 frames), and maybe it is actually a better number than one might expect because most of the "excess" area (sprocket region and other wasted area) isn't developed. However, don't forget the leader, which is very dense and therefore uses up extra developer.

 

[fhovie]

Please please please! - If your car gets 20 miles to the gallon and you need to go 20 miles, do you put one gallon in it? If 1L of a very weak developer will do 1 8x10 of surface area. I will develop that roll of film in 1.5L so that I won't ruin a lot of work and so that I can get consistent repeatable results. Developer is cheap - if it is not - you are making it wrong.