Clip tests

[Mike Panczenko]

I have sent film in for clip testing numerous times but wonder, beyond checking dmin what do they do?

 

Do they check for physical damage, xrays, check to make sure emulsion matches the can (to make sure misidentifaction is not the issue?), do they check age and mfg. date, or is it just a yes/no? Which is what I've gotten usually. What is standard lab opertating procedure ? Also is it the same as a sensiotomic test?

Edited September 13, 2009 by Mike Panczenko

[Adrian Sierkowski]

As far as I know they're just telling you the density on the neg, from which you can figure out how badly fogged (if fogged) it is.

[K Borowski]

Well, since you can normally spot most of that stuff visually, the only inspection is that of a skilled operator.

 

The chances of a skilled operator mixing something like that are practically nil, no offense.

[Mike Panczenko]

Well, since you can normally spot most of that stuff visually, the only inspection is that of a skilled operator.

 

The chances of a skilled operator mixing something like that are practically nil, no offense.

 

 

I wasn't talking about myself Karl- I'm wondering about SE distributors, in particular. One SE place I get film from prints the RGB levels on the can tape itself. But others do not, so I will often send those rolls in for clip testing anyways- I rarely act as a DP, so the amount of film I actually shoot when I do get the chance is low enough to be able to afford the scattered clip test. Considering though that different emulsions have different base fog densities, I was curious how thorough an inspection the labs will do on the film. For example, if film was bought from a SE reseller that came from a student film- I would necessarily trust that the can would match the actual film. So when they do the clip test, if they did not actually inspect the emulsion to ensure it matches the can, they could be providing an inaccurate Dmin to compare to. Also, physical damage such as pressure marks can be there, but not in image area. Basically, problems can be there beyond basic age fog.

 

So how in depth do they get when they clip test? Are they checking the edgecode to make sure it matches the can, then comparing it to the Dmin values they have for that particular stock? Are they doing an eye inspection to, or is it just thrown onto the densitometer and given no in depth visual inspection, to ensure no physical damage or abberations outside of picture area? That's more what I'm getting at.

[Charles MacDonald]

I have sent film in for clip testing numerous times but wonder, beyond checking dmin what do they do?

 

Do they check for physical damage, xrays, check to make sure emulsion matches the can (to make sure misidentifaction is not the issue?), do they check age and mfg. date, or is it just a yes/no? Which is what I've gotten usually. What is standard lab opertating procedure ? Also is it the same as a sensiotomic test?

If you ask nicely, the lab may be persuaded to return the "clips" and then you can check the edge print for type and date. Normally they will just junk the blank clip or use it as leader on someone's film. Checking for d-min covers both heat and x-ray fog, and if the film is NOT uniform the test would be an automatic fail.

 

If they detect physical damage they would be reluctant to run the film at all for fear of having to rethread the processor.

 

A sensometric test is similar, but the sample is exposed to a step light source and the density is plotted to make sure that the film covers it's curves. This is more likely to be done to check out a processing line than to check out film itself.

[Mike Panczenko]

If you ask nicely, the lab may be persuaded to return the "clips" and then you can check the edge print for type and date. Normally they will just junk the blank clip or use it as leader on someone's film. Checking for d-min covers both heat and x-ray fog, and if the film is NOT uniform the test would be an automatic fail.

 

 

 

Very interesting! I did not know it covered heat too. Now since they do not automatically check the edge print for type and/or date, this makes me wonder: Do all modern emulsions have the same dMin? Is a clip test stock-agnostic? I send it in and I get word on the film, but my question last week made me curious more about the nitty-gritty of all this. I did arrange to visit a lab in about 2 weeks, so I'm sure that will solve many questions, and raise many more!