Test strip print calculator
Is it worth to get one for the exposures tests? Or can I make one in a transparent acetate sheet? I getting a bit of trouble in doing the traditional way, the print always come ups to dark. I cover almost all the paper, expose for 2 seconds, then slide the covering a bit and exp. 4s, then 8 then 12 or sixteen, etc. the final exposure is made with out any cover (right or wrong?) and that small last part should correspond to the 2 seconds, since the first one will always got light, corresponding to the longest exposure time and being the darkest. Yes? Or I am completely east of eden?
If I have understood what you do then you gradually uncover the paper until at the end the whole paper is uncovered which means that the whole paper gets whatever exposure you give the last section so if the exposures are doubled each time and you give say 5 exposures of say 2,4,8,16,32 then the least exposure is the last with 32 secs and the most is the first with 32+2+4+8+16= 62 secs.
Originally Posted by Rhodes
No wonder that it is all too dark. Try 2 secs then cover that section then 4 secs and cover that section and so on. This will give you 2,4,8 etc which is your aim.
It can get confusing. For the price of the Firstcall calculator you can buy a Paterson 5 strip printer which allows you to uncover then cover each strip for the exposure which is what I have tried to describe above. If you have to uncover then cover with plastic strips it is impossible to make mistakes. The Paterson also allows you to select the best part of the negative and then move the test strip printer each time so the same section of the negative is printed each time. All you do is close all the strips then move the printer until the second strip is under the same section of the negative then open that one for say 4 secs if the first strip was 2 and so on
You want to cover the paper progressively as you make strips. So start with an uncovered sheet and make your first exposure. Cover a small strip, make another exposure, repeat until you have made strips on the whole paper.
There are two schools of thought on the timing for the strips. First is equal number of seconds for each strip, so you end up with 2, 4, 6, 8, 10... This is easy to do with a regular timer, which is why it's popular.
The second method involves using fstop printing so each strip gets exposed with twice as much (or some fraction of a stop) as the pervious strip. For example 2, 4, 8, 16, 32... As you can see in 5 strips you have covered a range of 2 to 32 seconds vs 2 to 10 seconds. In addition each strip will be denser than the previous one by an equal amount. The downside is with a regular timer it's difficult to get the calculations right.
I recommend you stick to the first method for now. Make large strip increments to get you into the ballpark, then make another strip with smaller increments to fine tune the exposure. So start with a sequence of 10 second exposures so you will have a strip at 10, 20, 30, 40, 50, 60 seconds. Then, if for example the 30 is too light and the 40 is too dark make a second strip. Give the whole paper 30 seconds, and then make strips at 2 second increments. So you then have 30, 32, 34, 36, 38, 40. If the ideal looks to be between 34 and 36, then a 35 seconds exposure should be just about right.
If you want to explore fstop printing I can recommend it, but I think it really requires a timer that supports it built in. There are many threads on the subject, but I wouldn't worry about it for now. The only reason I brought it up was your times you quoted looked like you might have been attempting something like this.
Last edited by L Gebhardt; 12-15-2013 at 09:50 AM. Click to view previous post history.
Just to be sure, you need to start with the long exposure first. My example is 32 16 8 4 2 1 1. I then get a test strip with 64 32 16 8 4 2 1.
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+1 you must cover the test strip in steps.
Second section will get the initial 2+4=6. If third exposure is eight third section will get 2+4+8=14. So second/first=3x, too large ratio.
Try 2 secs then cover that section then 4 secs and cover that section and so on. This will give you 2,4,8 etc which is your aim.
What I do. Have a stopwatch with three nice big pushbuttons start, stop and reset. I let the stop watch do the sums for me. One hand for the stopwatch, the other for the enlarger switch. Assume I want a sequence 2, 4, 8, 16 seconds. Expose whole 2s. Mask first cm (or 1/2 inch if you prefer). Expose until the stop watch is at 4s. Advance mask one step, expose until the 8s mark. And so on.
(A) 2s is actually too short to be reproducible. Useful only for a first rough estimate. Aim for an exposure time of 10s at least; close the lens diaphragm if necessary.
(B) When you need to nail down the exposure, you need finer steps for the intermediate times. I use 1/2 stops, which is not hard to memorize, because it's just the sequence of f-stops 2, 2.8, 4, 5.6, 8, 11, 16, 22, etc... Except the difference between two steps is 1/2 stop, not 1 full stop (as would be the case if you dialled these numbers on the aperture ring). With a paper grade 3 or more, I use 1/3 stops; also easy to memorize because it's the sequence of ASA/ISO sensitivities; but leave that for a later time once you have digested the basics.
[C) You seldom have samples of important tones all present in the small area covered by a test strip. You may need to expose two test trips in different areas. Then develop/fix together; saves time.
(D) Be aware of drydown: light print tones will be slightly darker once the paper is dry.
I have one and yes they are really handy.
Mark Barendt, Beaverton, OR
"We do not see things the way they are. We see things the way we are." Anaïs Nin
To the OP:
Don't get confused by the seemingly contradictory progressions for making test strips. There are two different techniques at work here.
Some (like me) start by giving the entire test strip a base exposure and then cover it progressively in predetermined intervals (like 2,4,6,8 seconds, etc.)
Others (like Christopher Walrath above) start with most of the test strip covered and uncover it progressively. The intervals are appropriately different.
Either method works fine, as does the print projection scale. Use whatever method is comfortable for you.
FWIW, I like the flexibility of a test strip over a projection scale so I can use whatever values I like (plus I don't have to buy a projection scale )
I also like a progression of percentages so that each strip is the same exposure difference. However, it really doesn't make that much difference. The main thing is to find a base exposure that you can begin with and make refinements from there.
After a darkroom afternoon time, well I get a more normal results, but still not get a decent test strip. The trouble with the Paterson test printers is that it only exist in 4x5, and I am falling in love with 8x10 paper!
No sweat. You do not need to cover the entire paper with the printer in order to get a good exposure indicator. Just make certain to center it under the projection of an important portion of the subject. You will get enough to make a good determination.
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