Wet film

[MarkH]

This thread might put the cat amoungst the pidgeons.Many moons ago I first got interested in photography not long after the dawn of the SLR. I quickly learnt the difference of quality between fast/slow ASA and cheap/ expensive film. I appreciate the opportunity for computer processing digital images but has anyone considered the use of good quality wet film with guided equipment. If anything from experience I have found digital equipment to be much less versatile than wet and wonder if we are all missing a trick........???
?? Any comments?

[ApophisAstros]

how much film would you need for a lengthy imaging session?
how would you know if each sub was ok or not?
Roger

[MarkS]

Quote from https://en.wikipedia.org/wiki/Quantum_efficiency:
"Photographic film typically has a QE of much less than 10%, while CCDs can have a QE of well over 90% at some wavelengths. "

Also you'll need to go somewhere very dark indeed to prevent the long exposure becoming orange with light pollution.

But don't let me put you off trying 

Mark

[Carole]

I have never tried it for astro imaging and never developed film even in the old days, so no plans to start to do that now.

How would you process it, I guess you can't.

Carole

[Roy]

I believe that wet film still has a greater dynamic than digital, but I don't know what the equivalent in bits would be - a quick search of the Internet did not give a definitive answer.

One problem with using film for astro-imaging is reciprocity at low light levels, which was why photographers used to in effect increase the films sensitivity by exposing it to a short pulse of light.

Roy

[NoelC]

An interesting proposal Mark - we look forward to seeing your results...

I'm with Mark S on this, the sensitivity of digital sensors is far greater than the most sensitive film and allows for noise reduction techniques that cannot be applied to film images.  Also, I think I am correct in saying; grain size in films increases with sensitivity.  Professional scopes used to compensate by increasing the plate size.  The dominance of F8 as a preferred focal ratio in smaller professional telescopes (such as the JKT in La Palma) in the 1970's came about because of the size of the commercially available plates and the grain size of the emulsion made by Kodak at the time.  But they were manually guided, and I'm sure you could import the negative as a hi-res scan and process it for gradients and light pollution.  It must be worth a try?

[MarkH]

My thinking was for one single exposure, guided using very slow film which has the finest grain. I guess some experimentation with light meter exposure times would be required. It did occur to me that the diminishment of wet film the witchcraft of guiding never really crossed paths. And of course there would be no processing as such only the manipulation you could do under an enlarger.