At what point in developing is film not light sensitive?

[Jehu]

I understood the fixer to be what makes the film insensitive to light. I accidentally opened a tube right after the developer with the light on. I finished the sheet with the rest of them just to see what it would do. I couldn't tell which sheet I exposed. I thought the sheet would be ruined.:confused:

Is it safe to open the film to light right after the developer?

[dazedgonebye]

I can't explain your experience. I would have said that about half way through the fixer was the first safe time to look.

[Gene McCluney]

Film developer is slow working by its nature. The film was exposed to light, and if left with developer in contact it would start to build fog density until the developer left on the film became exhausted. The "Key" here is time. If you had not continued with good haste in stopping and fixing the film, the developer "WOULD" have created some fog development.

In reality, once the developer is completely rinsed off the film, it should have no further practical sensitivity to light...it is still sensitive to light, but there is no developer to continue developing the white-light exposed silver-thus it remains undeveloped and can be fixed out in the fixer.

The fix dissolves the un-developed silver rendering the image permanent and transparent. Otherwise the un-developed silver would remain and the negative would be opaque, milky with retained un-developed silver.

I use Kodak Rapid-Fix, and I wait one minute before I turn on the lights, and the film is clear at that point.

[Lynn Jones]

Don't rely on this, because it depends on both the film and the developer, but after the film has been in the developer for most of its time, the light sensitivity is reduced by a great deal, once in the stop bath where the developer is either gone or de-activitaed, there is precious little sensitivity. Many times most of us have forgotten and opened the stop bath instead of the fixer and after re-capping it didn't matter. In a few instances, I have put film in water instead of fixer and imagine my shock when I saw the milky negatives. I just put them in fixer and found little or no difference.

As I say, don't depend on this but darned seldom has our stupidity hurt us in this regard.

Lynn

[Gene McCluney]

The early wet-plate process instructed the operator to rinse the plate with water after development then it could be brought out into the light and fixed. Perhaps this advice was because the portable dark-tents that photographers had to use to sensitize and develop the plates were suffocating and hot in summer, and the less time inside the better. Development was almost instantaneous with the old Iron developer.

[Brian Ellis]

People who use the BTZS tubes routinely move the developed film into the stop bath with the lights on. At least that's the procedure Phil Davis described for use of the tubes and that's the procedure I used for some 15 years. Once in the stop bath there's no further immediate concern with light. You certainly don't need to fix film in the dark. Nothing is going to happen to it after leaving the stop bath that would create any short-term problems. The only time I have the lights off in the darkroom when processing film is while the film is being put in the tubes and the tubes are capped. After that the lights go on and stay on.

[keith english]

As Brian said the BTZS system recommends going from developer to stop with the lights on. I dim the lights to jusst enough to see what I'm doing. Since theis is no further development their is no discernable fog and the fixer removes the undeveloped silver.

[Bob Salomon]

You may have raised the base fog by a measurable amount. Some workers pre-flashed their film in the past.

[Brian Ellis]

You may have raised the base fog by a measurable amount. Some workers pre-flashed their film in the past.

Film flashing is done before the film is developed, which is a whole different deal than exposing film to light after development is completed.

[Bob Salomon]

My point was that some films are intentionally exposed to light prior to developing. Opening the tube prior to fixing might raise the base fog level.

[D. Bryant]

My point was that some films are intentionally exposed to light prior to developing. Opening the tube prior to fixing might raise the base fog level.
Sorry Bob that just isn't going to happen during post development exposure to light. Those that don't beleive this should test it for themselves. As Brian correctly pointed out it isn't a problem and the late Phil Davis pointed that fact out too. So if it was good enough for Phil then it's good enough for me and it has been proven true in my darkroom.

Cheers,

Don Bryant

[Bob Salomon]

Sorry Bob that just isn't going to happen during post development exposure to light. Those that don't beleive this should test it for themselves. As Brian correctly pointed out it isn't a problem and the late Phil Davis pointed that fact out too. So if it was good enough for Phil then it's good enough for me and it has been proven true in my darkroom.

Cheers,

Don Bryant
You ever take a sheet of film out of the developer and leave it in a room with the light on prior to rinsing or fixing? What happened to it after a few minutes exposure?

[sanking]

No one is suggesting that film won't fog if you just pull it out of the developer and leave in room light without farther processing. It certainly will. However, in BTZS type procedure the cap is removed from the tube after development is complete, in room light or subdued room light as one prefers, and the tube is then immediately placed in a a tray of acid stop bath for 10-15 seconds. After 10-15 seconds in the stop bath the film is removed from the tube, in full room light if you like, and fixed in a tray.

I have developed hundreds of sheets of film this way, and in many cases where I was testing, measured densities with a sensitometer. There is no measurable fogging of the film with this procedure that the sensitometer is able to discern.

Sandy King




You ever take a sheet of film out of the developer and leave it in a room with the light on prior to rinsing or fixing? What happened to it after a few minutes exposure?

[Bob Salomon]

"sensitometer"

Densitometer?

Did you compare base fog against identical sheets that go into the fixer in the dark and were not exposed to light?

[sanking]

Sorry, I expose test film with a sensitometer but measure densities with a densitometer.

But no, I have never directly compared two identical sheets of film that were not exposed to light at all. I have compared identical sheets that were exposed to a step wedge with a sensitometer. The step wedge has a square about 0.5" in size that is covered by a piece of opaque black tape so for all practical purposes you could say this section of the film received no light.

Sandy King







"sensitometer"

Densitometer?

Did you compare base fog against identical sheets that go into the fixer in the dark and were not exposed to light?

[Bjorn Nilsson]

"sensitometer"

Densitometer?

Did you compare base fog against identical sheets that go into the fixer in the dark and were not exposed to light?

While I havn't done these densitometer tests myself, I do indeed trust the current sellers of the BTZS tubes, who claims to have made these tests with "positive results", i.e. no difference in between total darkness and a subdued but normal light. (I don't quote here, as I don't feel the need to watch the videos again, but that is the intention anyhow.)
What is more important is that after learning about this, I have been able to work in a more relaxed way in the darkroom, knowing that disaster will not strike because of having the lights on when opening a tank at the end of a developing run. With the CombiPlan, this creates ways of working in a faster, more streamlined way.
Finally, I have not noticed any added density, nor locally neither generally on the few negatives where I've indeed practiced the idea of dumping the developer by opening the tank in a subdued, but normal light and continuing by quickly adding a stop bath etc. There is no noticeable difference in printing times, nor in contrast to what I normally get.

//Björn

[Andrew O'Neill]

I did this once with Kodak IR film with no problems...strange.