TEST STRIP PROBLEM
Finally, I've set my darkroom up(durst M300) and I have started printing my BW negatives.
I have noticed that my test strip does not match the final print.
Of course, I did not change any setting or paper from test strip to final print.
Also, I have seen that if I make a test strip switching ON/OFF every 5 seconds the enlarger, makes darker strip than leaving the enlarger always ON.
Yes there is a difference between say, five 5 second exposures and one single 25 second exposure. I leave the enlarger on and, by the beeper on my timer quickly move the card an inch or so after every three (in my case) beeps. In this way, each segment of the test strip has received a continuous exposure for the time in question.
You should also compare a dried test strip to a dried print. A wet print looks much different to dried one.
I view my test strips as a "ballpark" approximation of the final print timing.
When I said "leaving the enlarger always on" I meant moving the card every 5 seconds while the enlarger was ON.
That is unusual - when there's a mismatch normally you get a lighter one because of the switch-on time of the lamp and/or stabiliser. What sort of timer are you using? If it's not a digital electronic one it's quite possibly out of calibration; maybe 5 seconds is really 5.5 for instance?
Originally Posted by gfevan
Define 'ball park'. I try to get highlights to within 1/12 stop and test strip for that. If my final print is out more than that, why make one?
Originally Posted by Mike Kennedy
Have you ever tried it the other way around, moving the paper instead of the card? This way, test strip and final print match exactly, and you can test strip any area of interest and not just across a changing subject.
Originally Posted by gfevan
1. Take a big thick card and cut a hole into it, the size of your typical test strip.
2. Put the card onto your baseboard and position the hole where you want to have the test strip.
3. Tape the card down on one side, so you can lift it up like the page of a book.
4. Lift it and put your paper underneath.
5. expose the first test strip.
6. Now move the paper and do it again for a longer time.
It takes longer, but is very accurate and allows you to get the right time for exactly the spot on the print where it matters. If you like it, you can buy or make yourself a fixture which makes this all a lot easier.
You find better instruction at my website under:
My test strips are not strips at all but two small full frame
prints printed 2-up on 5x7. I've been turning the paper 180
degrees for the second exposure. The paper though could be
pulled half way through the easel; easy with the 5x7 Speed
Easel. Full frame exposure tests. You'll like them. Dan
You can get a multiple test strip and the final print to match exactly.
If you are doing the timing by jerking the cardboard with the enlarger on, or using an analog timer, then results shouldn't be expected to match.
The turn-on and warm-up time for a PH-2xx enlarging bulb is on the order of 50 milliseconds, for the average 5-step strip with 5-10 second intervals this time can be ignored for most purposes. If you are using a cold-light then the only way to get really exact results is with a shutter, though you may find an integrator/compensating timer gives acceptable results.
An application note describing how to find the lamp turn on delay.
I like that. Very good technical note. It's a keeper, but the type face... ?
Originally Posted by Nicholas Lindan