TEST STRIP PROBLEM

[gfevan]

Hi,
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.

 

[BobNewYork]

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.

Bob H

 

[Mike Kennedy]

I view my test strips as a "ballpark" approximation of the final print timing.

 

[gfevan]

When I said "leaving the enlarger always on" I meant moving the card every 5 seconds while the enlarger was ON.

 

[RH Designs]

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.

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?

 

[RalphLambrecht]

I view my test strips as a "ballpark" approximation of the final print timing.

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?

 

[RalphLambrecht]

When I said "leaving the enlarger always on" I meant moving the card every 5 seconds while the enlarger was ON.

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.

Try this:
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:

Dead Link Removed

 

[dancqu]

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

 

[Nicholas Lindan]

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.

 

[RalphLambrecht]

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... ?

 

[dancqu]

View the Entire Negative Exposure Tests

You can get a multiple test strip and the final
print to match exactly.

The 2 up on 5x7 method I've mentioned in post 8 is a straight
forward, most reveling, real world method. At least a several
second exposure is needed each print. Up to the entire area
of the negative may be printed then evaluated.

I've abandoned strip testing. For those who use an Enlarging
meter of who's ever manufacture the step up to full size
prints is simplified. Dan

 

[Nicholas Lindan]

I like that. Very good technical note. It's a keeper, but the type face... ?

"Swiss721 LtEx BT", Arial-like. What is showing up at your end?

 

[RalphLambrecht]

"Swiss721 LtEx BT", Arial-like. What is showing up at your end?

A very stylish type face with huge capitals and extremely small lower-case letters. Attached is a screen shot.

 

[mike c]

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

Dan could you elaborate on your method of test strip. Whats 2up??

mike c.

 

[aparat]

I like that. Very good technical note. It's a keeper, but the type face... ?

I like the font

 

[Kirk Keyes]

Nicholas - the pdf looks like Ralph's does on my computer. It maybe Arial like, but it's not Arial. I think it's the extended font and the extra spacing in the words that make it look funky. Like something from Star Trek. That's fine for labelling Turbolifts and Jeffries Tubes, but it's hard to read your article that way.

 

[RH Designs]

Nicholas - on my screen it looks like Ralph's screen-shot too and is hard to read. Have you ticked the "embed fonts" box when you generate the pdf file? If not, results are unpredictable as the reader's computer will select one it thinks might be similar, but it's often wrong!

 

[Steve Smith]

I've abandoned strip testing. For those who use an Enlarging meter of who's ever manufacture the step up to full size
prints is simplified. Dan

I don't use test strips very often. Instead I cut a piece of paper into 2" or 3" squares, estimate the exposure and try it on an area with a good range of tones. After two or three of these 'test squares' I am usually there.

I bought a Paterson enlarging meter a few days ago for £2. I haven't had a chance to try it yet though.


Steve.

 

[dancqu]

Dan could you elaborate on your method of test strip.
Whats 2up?? mike c.

Two up is two prints on the same sheet. With a 5x7
sheet each print is about 3 1/2 x 5. The exact size
depending upon the negatives format.

I use a 5x7 Single size Speed Easel and cover half
the sheet with a card for each of the two exposures.
Quick and easy to do. Full negative exposures make
evaluation easy too. I may be doing some 5x7
testing using 8x10 sheets. Dan

 

[Nicholas Lindan]

Have you ticked the "embed fonts" box

Evidently not...

One more time http://www.darkroomautomation.com/support/AppNotePH212LampDelay.pdf

 

[RH Designs]

Yep, that works!

 

[Kirk Keyes]

I looks beautiful for me, too!

 

[RalphLambrecht]

Evidently not...

One more time http://www.darkroomautomation.com/support/AppNotePH212LampDelay.pdf

Perfect!

 

[mike c]

Well Dan, thanks for the replay . I'm still confused how the two prints on the one 5X7 make a test strip. Are you stepping the exposer on each print?

 

[dancqu]

Well Dan, thanks for the replay . I'm still confused
how the two prints on the one 5X7 make a test strip.
Are you stepping the exposer on each print?

I usually guess-timate a first least exposure then after
rotating the paper give a second exposure half again
longer. Often one sheet with the two exposures has
me in the ballpark and I'm ready to go with best
estimate to 5x7; one exposure.

What sold me on the method is having ALL of the
intended print's image available for evaluation.
I believe the method to be two or three birds
with one stone. Dan