Debshots Photography | Chemistry, Math, and Headaches

Chemistry, Math, and Headaches

March 28, 2017  •  Leave a Comment


As I mentioned in a recent post, I’ll be jumping in head first and shooting the first rounds of 70mm at Wondercon this weekend . . . and as I was planning and plotting and scheming my shoots I realized: I should probably figure out how I’m going to develop this stuff.

I’ve pointed out before, I’ll be developing the film myself, I have all the equipment for it but, here’s the thing, I’ve never developed my own color film.

Black and White yes, Color no.

This is going to be interesting.


I looked up the chemistry for color development and decided to buy Tetenal, for no other reason than I recognized the name, I actually have no idea how it’s going to work out.

Tetenal is sold in 1L and 2.5L kits, and I had planned to buy the 2.5L kit, but my purchase options ended up being more limited than I anticipated.

See, Tetenal has an ORM-D code, because it’s potentially volatile or something. I don’t care. What I care about is that this means Tetenal needs to be shipped ground. Not a problem, EXCEPT when vendors decide they’d rather not deal with ground shipping and just . . . make it unavailable. (Looking at you B&H) It’s okay, I bought from Freestyle instead, and even though it meant paying more, they got it to me the same day. Which was magical.
Not so magical is that I had to buy the 1L kit because the 2.5L is sold out until April.

Back to the issue at hand, 1L Tetenal is spec’d at being able to process 12, 36 exposure 35mm rolls. BUT my film is 70mm wide and 15 feet long, per roll, and then I got to thinking; how much freaking chemistry is this project going to take?

I hadn’t thought about it at all, at any point . . . shit.

It’s okay, I have science and math, I can figure this out . . . by creating the most convoluted word problem ever.


First Problem: How much 70mm film can I process in theory with a single kit of chemistry?

A single roll of 36 exposure 35mm film runs about 65 inches, or about 5 feet, and obviously 35mm wide.

I’m assuming the thickness of the film itself doesn’t matter. I hope it doesn’t. We’ll see.

Starting with the width, for every one roll of 70mm I would have the equivalent width of two rolls of 35mm. Therefore: for 12 rolls of 35mm, I would have 6 of 70mm.

Not accounting for the length of the rolls.

For each 15ft of 70mm, there are about 3 rolls of 35mm 36 exposure film.

Simple division tells me that this all amounts to two cartridges of 70mm.

A mere 30 feet (give or take) that I can get out of 1L of chemistry.

That’s a weekend.

That’s less than what I planned on going through this at Wondercon . . . I guess my chemistry won’t get old, it won’t be around long enough.

And then a thought occurred to me:

I can shoot 15 feet at a time, but how much can I process at a time?

According to a site that sells the Paterson tanks that I use, the plastic reels hold a single 26 exposure roll of 35mm.  

Which, okay great.

EXCEPT my rolls of 70mm are 15 feet long.

Well this is going to suck.

My options are to either only shoot 5ft at a time . . .


Cutting the roll. Sacrificing two frames, and be able to shoot what is effectively 3 rolls of film at a time.

I hate the idea of cutting two frames in half . . . but not having to change the rolls basically all day, damn, isn’t that part of why I’m doing this?

I have to decide what I’m going to do before I roll the film, which I plan to do before I travel to Anaheim for Wondercon.

I’ll give myself tonight to think about it.


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