Rodinal: Dilutions

[AdamB501c]

So typically TX developed in R09 is 7 minutes at 1:25, at 1:50 what's the development time?

[Old-N-Feeble]

W-a-a-a-y back when I processed B&W... my reason for higher dilutions (usually 1:100) was for better shadow detail without blocking highlights. I underdeveloped then increased negative contrast with selenium toner. This effectively lengthened the straight portion of the H&D curve (gamma curve) and improved micro-contrast. Ilford Gallery #3 was my favorite paper... also selenium toned to deepen shadows without blocking them. Selenium also improved the olive drab tone of Gallery papers to a nice very slight plumb color... very pleasant... and it improves archival qualities.

[Leigh B]

One difference is economy. With higher dilutions, you will be getting more mileage out of the dev.

You need a minimum of 10ml of concentrate per roll regardless of the dilution used.

With smaller tanks this may preclude use of the 1:100 dilution.

- Leigh

[Jüri]

You need a minimum of 10ml of concentrate per roll regardless of the dilution used.

With smaller tanks this may preclude use of the 1:100 dilution.

- Leigh

My tank requires 400ml for a roll of 35mm so I've used only 4ml of developer when doing stand development. I haven't had a lot of practice, but 4 ml has worked. Is there some sort of calculation that concludes I need 10ml or is it just a manufacturers recommendation?

[Leigh B]

It's just manufacturer's recommendation, like lots of other things.

There are innumerable individuals who feel they know more than the manufacturers on any particular subject.

- Leigh

[Sal Santamaura]

...Is there some sort of calculation that concludes I need 10ml or is it just a manufacturers recommendation?

The manufacturer established that 10ml of concentrate is required per 80 square inches of film developed to be certain that sufficient active ingredients are present, i.e. to avoid exhaustion. This is based on the worst case. There is a chance that, depending on scene content, less than 10 ml will still provide adequate active ingredients, but one cannot be certain.

It comes down to "confidence or crap shoot."