Process promptly for best results

Process promptly (within 7 days) for best speed and contrast.

You may experience latent image degradation when you develop your summertime pictures after the holidays.

Conversely, you may get amazing contrast and speed when you develop your film right away in excitement.

Last month I caught up a year old backlog. I graphed different speed and contrast from the same film developed in the same tank for the same time. I checked old notes and saw the same. Times when I struggled to reach contrast aims, the latent images tended to be older.

When I load cassettes from bulk rolls, I will place sensitometry exposures on the leader of half the rolls and mark “6 for sens” as a reminder to wind past 6 before shooting (the other rolls will have a full 36 exposures).


Naturally, pre-exposing test strips causes old latent images for sensitometry if you don’t develop promptly.

Sometimes I’ll pull a length from the bulk loader and expose a fresh sensitometry strip to put in the tank. For example when there’s room for another reel because I only have a few rolls to develop, or if none of the rolls has a test strip on it already. These will be fresh.

In those examples a tank can have an old and a new sensitometry strip of the same film and when graphed, will reveal different speeds and contrast.

Not just test anomalies. These are real differences with practical implications. Carefully-exposed shots that would be excellent if processed promptly can come out underexposed and flat if you leave the film lying around too long. Too long is about a year.

Well done Bill! By your opinion, what are the best option for people without sensitometer?
40 years ago, at University I had Sensitometry course, but I do not have any desire to buy one.
For New year I bought BW densitometer from our own Derek and I'm thinking about creating "target" with different patches to use it for comparing my film developing.

Do you store exposed films at room temperature, or do you put them in a freezer? Of course, in their snap lid plastic can (or aluminum).

That is nice that you have the pre exposed Control Strip on the film leader!

Good stuff Bill. I'm the king of letting exposed rolls languish for months.

gorbas said:

Well done Bill! By your opinion, what are the best option for people without sensitometer?
40 years ago, at University I had Sensitometry course, but I do not have any desire to buy one.
For New year I bought BW densitometer from our own Derek and I'm thinking about creating "target" with different patches to use it for comparing my film developing.

Click to expand...

Thanks gorbas

I would start with a Stouffer Scale such as T2115 and an electronic flash on an old school contact printer. I’d rig it up “permanently” so that it’s always ready to flash a test strip. An enlarger makes a good sensitometer with the same Stouffer Scale but you would end up with Tungsten speeds.

Kodachromeguy said:

Do you store exposed films at room temperature, or do you put them in a freezer? Of course, in their snap lid plastic can (or aluminum).

Click to expand...

Probably a contributing factor is how poorly I store exposed film. I keep it in a little cabinet with chicken wire doors. It’s an uncontrolled environment, on a shelf in my darkroom which is in my garage a few blocks from the beach.

Fresh film where I exposed the test strip is stored in a wine refrigerator.

ic-racer said:

That is nice that you have the pre exposed Control Strip on the film leader!

Click to expand...

It’s convenient to get out the sensitometer when loading bulk rolls. I like to bulk load in the dark (so I don’t ruin the last couple shots).

Pan F is notorious for the latent image to fade away over time. The strength of the frame numbers is an indication of film age since those are exposed onto the film during manufacture.

Pan F is the only film I've ever seen a need to worry about this with. I shot Neopan 400 at 3200 and developed it by accident at 400 ten years later (no refrigeration) and still got a bunch of usable pictures (hybrid process). However if I shoot that same film stock from that batch today, I only get maybe 100 speed out of it. So from what I've seen shooting expired film gives worse results than waiting to develop your film for the same amount of years.