Evaluating negatives: after development/stop?

puketronic · Jun 12, 2012

If you want to do a quick evaluation of a negative, when can you expose it to light? After development/stop? When I want to check purely for light leaks/lens sharpness, I don't feel like going through the whole ritual.

Bill Burk · Jun 12, 2012

If you use an alkaline fix, you should process fully including fixation.

There's plenty of threads discussing the possibility of further development in that case - and if you were looking for light leak symptoms you might get a confusing test result.

puketronic · Jun 12, 2012

Got it, so in otherwords: no shortcuts.

Doremus Scudder · Jun 12, 2012

You can turn on the white light after half the time in the fix (assuming you've done a clip test and the film clearing time has been established). I always wait a bit longer for "real" negatives, but for a test, you should be okay.

Best,

Doremus

www.DoremusScudder.com

Gerald C Koch · Jun 13, 2012

It would be very difficult to evaluate an unfixed negative. You are talking about saving 5 minutes. Since you don't want to go thru the whole ritual, have you considered digital photography instead.

RalphLambrecht · Jun 13, 2012

i never expose a film to lightbefore the 1st fixin bath...too risky!

cliveh · Jun 13, 2012

If you are that keen to view your negs prior to fixation, why not develop with occasional inspection to a dark green safelight, assuming we are talking black & white panchromatic.

Maris · Jun 14, 2012

I do this with 8x10 black and white negatives to freak out darkroom visitors: turn on the tungsten lights after the neg has been in well agitated acid stop for 30 seconds. So far I've never had fogging even with several minutes looking and I've checked and double checked. Constraints include good stop bath, no extended inspection under fluorescent lights, and no sunlight.

By the way, a developed but unfixed neg is a strange looking thing and using it as a guide for subtle effects is pretty dubious.

Bill Burk · Jun 14, 2012

1st Generation IR devices are very much more affordable than they were 30 years ago.

Developing negatives and watching them emerge is as much fun as watching prints emerge.

pentaxuser · Jun 14, 2012

The post by maris has set me thinking. I know he is clearly saying that exposure after a rigorous stop has been fine but I think that this means that the stop has done something that is irreversible i.e. if for instance the neg hasn't been developed enough there can be no question of pouring the dev back in and carrying the development further.

If I have got this right then what is the irreversible chemical action that prevents further development? Presumably if water stop has the same effect of stopping development then presumably this too is irreversible. So is this the same irreversible chemical action by water as by acid stop and if so what is it that prevents further development after a water stop but has no effect on development when water is simply a pre-wash?

Thanks

pentaxuser

Bill Burk · Jun 14, 2012

pentaxuser said:
If I have got this right then what is the irreversible chemical action that prevents further development?

In the case of acid stop, I get the feeling what happens is the pH changes so development activity is quickly reduced. You could rinse the film off and put it back in the developer if you wanted to. But if you had turned on the lights, it would start to turn black (you would get Sabbattier effect which is pretty cool).

In fact a few weeks ago I accidentally dropped a sheet of film in the stop first by mistake. Still in the dark, I quickly realized the mistake and pulled it out and dumped it in a bucket of water I had handy. Then I went on to develop it normally and you can not tell the difference. Stop bath didn't cause irreversible change.

pentaxuser · Jun 14, 2012

Bill Burk said:
. You could rinse the film off and put it back in the developer if you wanted to. But if you had turned on the lights, it would start to turn black (you would get Sabbattier effect which is pretty cool).

.

Thanks Bill. So the correct light by itself(i.e. not daylight or fluorescent) changes nothing as long as it is then fixed. It is the combination of light and further developer. The stop only "stops" as long as it is dark or if in light fixer is then applied. Using stop be it water or acid does not prevent the process being continued as long as the film has remained in the dark. If the processor suddenly realises that the dev time was wrong he/she can continue. Nothing is lost. Most here might realise this but others might think that there is no hope if stop has been applied and end up with an underdeveloped film which could have been saved.

However there is no "free lunch" and no question of being able to check film in light and then continuing development other than the very dim green light approach which might work if you had lots of experience of checking film under such light.

The maris approach would save the waste of fixer in the case of light leaks as the OP mentions but have no other benefits as far as I can see.

pentaxuser

Bill Burk · Jun 14, 2012

pentaxuser said:
... other than the very dim green light approach which might work if you had lots of experience of checking film under such light.
...

The maris approach would save the waste of fixer in the case of light leaks as the OP mentions but have no other benefits as far as I can see.

Very dim green light will reveal obvious issues like a neg where the flash didn't go off (or you might recognize an interior shot you expected would be underexposed)... Then you can know to develop longer to have a chance to get a print.

Infrared viewers are really cool for the same reason.

The maris approach is great to show mastery over the darkroom.

But there is a practical reason to understand if some light (like from a 40 watt bulb) can safely shine on film, after developing right when film goes in the stop bath.

BTZS tubes are designed to be used that way, and many people report they don't have any problem with fog or Sabattier effect. I originally took the position it was safe, but was corrected by a scientist who explained that the process should be tested with alkaline fixers before saying it is safe for everybody.

removed account4 · Jun 14, 2012

as cliveh and bill say a green safelight works wonders to develop by inspection.
the dark green filter is dark enough that with room light on
you can barely see it is on
but in darkness, when your pupils are BIG you can see pretty well with the safelight.
i DBI often ... its kind of fun too ..

Andrew O'Neill · Jun 14, 2012

After 1 minute in the fix (rapid fix), I turn the lights on.

Bill Burk · Jun 14, 2012

Andrew O'Neill said:
After 1 minute in the fix (rapid fix), I turn the lights on.

One day my tempering bath overflowed into the last 16 ounces of fix I had. I caught it but not before the water had seriously diluted my fix. I had to fix that batch of film for 20 minutes. Lucky I had my IR scope and could tell the film wasn't clearing.

Gerald C Koch · Jun 15, 2012

puketronic said:
I want to check purely for light leaks/lens sharpness,

What seems to have gotten lost in this discussion is that fact that you cannot check for lens sharpness with an unfixed negative. This is because the undissolved silver halide will obscure any fine detail. In fact the negative must be fixed, washed and dried before lens sharpness can be quantitively determined.

Bob Carnie · Jun 15, 2012

I look at 8x 10 negs seconds after going into the fix when I am doing solarizations.. I want to see the black line and then move on to the next set of negs and work through an afternoon this way.
I have seen no issues with the film. It freaked me out the first time trying this but I use an acid bath and within ten seconds the film clears out so I can see it..

pentaxuser · Jun 15, 2012

Bill Burk said:
But there is a practical reason to understand if some light (like from a 40 watt bulb) can safely shine on film, after developing right when film goes in the stop bath.

BTZS tubes are designed to be used that way, and many people report they don't have any problem with fog or Sabattier effect. I originally took the position it was safe, but was corrected by a scientist who explained that the process should be tested with alkaline fixers before saying it is safe for everybody.

I am confused again Bill. Are you saying that BTZS tubes allow the very thing that I had concluded was impossible based on your explanation, namely the ability to examine negs after developer under a 40 watt bulb and then presumably to safely increase development if required?

Thanks

pentaxuser

cliveh · Jun 15, 2012

No, usually an acid stop bath is used that neutralises an alkaline developer, but silver halide remains that is still sensitive to light. Water is usually pH neutral. The fixer (usually acidic) dissolves the unexposed silver halide making the image fixed.

tkamiya · Jun 15, 2012

With most traditional films, complete fix happens in 2 minutes time if using a Rapid Fixer. Double that and some with traditional fixer. Tmax will take double that. Either way, it's pretty quick.

Since OP is using 35mm format, unrolling the film to inspect is basically really not an option, not to mention seeing if there are problems with wet film isn't easy either unless the problem is severe.

It's far easier and practical to switch to rapid fixer if not already and do the complete processing.

Bill Burk · Jun 15, 2012

pentaxuser said:
I am confused again Bill. Are you saying that BTZS tubes allow the very thing that I had concluded was impossible based on your explanation, namely the ability to examine negs after developer under a 40 watt bulb and then presumably to safely increase development if required?

Thanks

pentaxuser

Sorry if it's confusing. No, the idea is not to do inspection and possibly continue.

The idea of the BTZS tubes is to develop for the allotted time, open them up and roll them in the stop bath tray - then in the fix. It's only "incidental" light that gets into the tubes because you opened them up at the end of development, while working comfortably under the light of a 40 watt bulb. You should leave the film in the tubes until you take them out to wash. The less handling the better, fewer chances of scratching. The design is simple, the tubes don't need light baffles. Each sheet of film gets its own tube, so processing is very even.

The hypothesis is: With acid stop and acid fix, processing stops immediately, so even though you exposed the film, you don't develop it any further so there is no measurable effect. The challenge to the hypothesis is: With neutral stop and alkaline fix (a popular combination these days), development of the (now) exposed film continues and the effect might be measurable. It's not likely to be serious, but you never know until you try.

The design is brilliant. You get even processing and few scratches... the holy grail of sheet film processing...

pentaxuser · Jun 15, 2012

Thanks Bill, I now understand. In effect the BTZS tubes do what Roger hicks calls the "Ilford Trick" which is that when Ilford demonstrated film processing the demonstrator used to remove the film from the developer in full roomlight and plunge into fix in what appeared to be a casual manner without ill effects.

Apparently the "trick" relies on speed in that there is a very short period in which the light fails to affect the film between dev and fix, so not really as casual as it appeared to the audience. Roger gives a better explanation but this in essence is or was the trick. I say "was" as Ilford may not have demonstrated this since the days when film was all there was to record pictures. Must have appeared pretty spectacular

pentaxuser

dehk · Jun 15, 2012

I just don't see why, unless you're shooting LF. And its still hard with a green light and you only can take a very quick look at the most.

Bill Burk · Jun 15, 2012

Oh it affects the film alright, it's still very sensitive to light... It's just that, you know, it took several minutes to develop this far... and you sure aren't developing even one more minute. So you don't ruin the negative that developed so far as a result.

But like a tree being cut down, the film is screaming when you turn on the light, even if you can't hear it.

Evaluating negatives: after development/stop?

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