Topic: Clip Testing Film

[Mike (happyforest)]

Has anybody tried this clip test. To determine an approx starting point for film\developer testing?

"Clip test
This can also be used to determine an approximate developing time for an unfamiliar kind of film.

Cut off a small piece of the film and develop it in full room light, using the development time you consider most likely to be correct. Wash it in water, fix it in fixer, wash it again, and let it dry.

Then compare your sample to the fully exposed end of a correctly developed roll of the same or similar film. Your sample should be almost but not quite black; strong lights should be visible through it. If it's not very dark, increase development or mix fresh developer; if it's pitch-black, use a shorter developing time. "

This comes from http://www.covingtoninnovations.com/xtol/index.html

Thanks

Mike

[Blaxton]

I haven't tried this.  It's the first I've heard of it, actually.  It makes sense in some ways but I wonder if it would  get you any closer to choosing a starting point for development than the manufacturer's suggestion. 

I plan to develop some film later this evening.  Maybe I'll give this a try.

[Mojave]

I know that A&I Photographic does it but I have never done it myself. My understanding is that they do it at A&I to see if they need to push or pull the developing. I dont trust it myself and prefer to let the chips fall where they may in regards to my exposures. I try not shoot at anything other than the specified ASA of the film and metering for shutter speed and aperture with a digital camera, if Im not sure about the light.

[Mike (happyforest)]

Blaxton.

The film I am trying to use is Tech Pan.  I've used Acutol in the past with some success and I've tried Xtol using 1:5 dilution but the film didn't develop fully nice light greys.  Similarly I have used Rodinal recently and had both extremes grey like the Xtol and extremely dark\over developed.  All times\dilutions have been researched on the web.  Of course the other issue which I will need to bottom out is what to rate the film at but I need a reasonable development time.

I do intend to have a try over the weekend with this but just thought I see if anybody here has tried it out.

I suppose this test is akin to finding the minimum exposure to achieve maximum black on printing paper, where the paper is developed to finality.


Mojave

This clip test is different to my understanding of how clip test are carried out in traditional processing labs.  Where they trim a few frames from the exposed film, develop as normal and assess contrast etc. then adjust the processing time for the remainder of the film.

Thanks for the replies.

Mike

[Francois]

What I do see in this procedure is that since it is processed in full room light, there should be a strong sabattier effect which will alter the densities quite some bit...

Usually, a clip test is done by loading a piece of exposed film (in the dark) that is processed properly in a regular tank. Once the processing & fixing are done, density is compared to what it should be and a second clip test is done to verify if the results are OK. If not, the test continues until it is considered good enough.

[Pete_R]

Doesn't make sense to me. Development is linked to exposure so if you fully expose the film the development required to get Dmax will be minimal. But as you'll never fully expose the film when shooting normally, the development time you determined from the clip test will be useless. At best, you could say it will give you the minimum development time.

[Photo_Utopia]

Has anybody tried this clip test. To determine an approx starting point for film\developer testing?

I think the test is only to confirm that your developer is still active, I don't think you can use it for film/developer time evaluation.

[Mike (happyforest)]

Thank you all for your thoughts on this technique.

As previously mentioned I am trying to determine the time required to develop some technical pan.  I have previously used times taken from the massive development chart with mixed results generally the film has been under developed, typically the film leader extremely light in colour.

I have been thinking about how I could use this technique for a little while and at least one flaw with it is that you have to develop for a fixed time and for me this is a problem.  I have no idea where best to start. 10, 20, 30 or XX minutes.

So I decided to modify this suggested technique a little.

I developed several small strips of film as recommended, but at various intervals removed a strip and fixed it.  Creating a sort of test strip.

 I then used these to visually decide when increased development seemed to given no further benefit to density. Very subjective I know but the best I can do without having the means to measure density.

The starting time I chose was taken from the massive development chart.

Rodinal dilute 1+150 for 7 minutes.  (This is for film rated at 25asa, my next problem to solve.) (My stand development dilution as 1+100 for 60 minutes so the 1+150 seemed a reasonable compromise.)

The intervals chosen were:  3.5, 7, 10.5, 14, 17.5, 21, 24.5.

Having compared them side by side, I determinate that 17.5 mins seemed to be the point were there was little increase in density for the extra time.

I have quickly run a short roll (three frames) through the camera nominally rated at 25 asa, developed using 17.5 minutes and got reasonable negatives.

Still room for improvement but I have a better starting point than I have had previously.

Thanks once again.

Mike

[Francois]

Well, your technique is good.
Using the test strip method is no worse than separate timings.

One way to judge density by eye is to hold up the film on a piece of written paper... Here's a shot of the Kodak book where they explain it.

[Mike (happyforest)]

Francois

Thanks for this.  I'll see how these negatives\stand up against the text test.

With the three frame test I did I used the auto bracketing feature on the camera.

This took three images one at 25iso one at 0.3 EV (32iso?) under and one at 0.3EV (20iso?) over.

The photo attached above is the 0.3 EV under, which to me seemed the best of the three.

Mike