Test strip times and printing times

[nlochner]

I dont have any problems with making multiple 5 second exposures....


Nlochner

[Photo Engineer]

Kodak used to recommend a single 60 second exposure with a cardboard covering the print for varying times. Thus the portion of the strip exposed for the full 60 seconds would be darkest and each of the sections would recieve 10 seconds less exposure.

There are three reasons why you should not use multiple exposures.

1. Light bulb on and off cycle is unpredictable. (timer error especially at short times)

2. Light bulb on and off afterglow is uneven and startup changes as the cycles continue. The bulb filament is warmer each cycle and starts differently. Hue changes as well with heat.

3. Less commonly known, some photo products don't respond evenly to multiple exposures. There is a kind of a reciprocity failure effect that is cumulative. This BTW, was a serious problem with earlier laser color papers as the overlapping scan lines got multiple exposures and the paper response was not the same as with regular white light exposure. That has now been corrected.

PE

[fhovie]

I never use a strip - I make a test exposure - usually my first guess is within one stop - then I use the fstop chart to make the next - since film esposure is not linear - I do not use a linear exposure strip - fstop charts are the way to go. You could probably invent one - each stop is twice the exposure as the next - mine is broken down to 1/3 stop steps and goes several stops plus or minus for each exposure time out to about 30 seconds max. Past that - do it in your head - We use stops when exposing the negative - I never understood why we would stop using fstops when printing.

[Edwardv]

Crikey.

I am kicking myself

After all these years [size=3][color=blue]it finally dawned on me[/color][/size] as to why most of the time my test strips didn't match the density of my prints !!!! I'm so stupid. I knew about the enlarger bulb warm up time, but never thought to factor it in.......

Arghhhhh!

Is there anyone else out there who has made or is still making this mistake, I need moral support by knowing you at least exist !

Yes, me too. Now I got a headache. But would this be compensated by a Zone VI compensating timer?

[Dan Henderson]

f stop printing based on non-incremental test strips makes so much more sense to me now that I've adopted the methods. And the bear so much similarity to the way the aperture and shutter speeds work in the camera that they are (or should be) second nature to a photographer. I really don't understand why students are not taught that way from the beginning.

[Dan Henderson]

oh yeah, I also wanted to say that Ralph Lambert has excellent directions for a test strip printer in his even more excellent book, "Way Beyond Monochrome."

[Paul Howell]

You can use a Kodak projection print scale, a pie shaped step wedge, place it over the print and set your timer for 60 seconds and read the print in seconds 2 to 48.

[nolindan]

On the subject of multiple short exposures == one longer exposure and the accuracy of progressive test strips:

With an incandescent enlarger, in my case a Beseler 45 and #212 enlarger bulb, several small exposures do indeed equal one long exposure.

Using a grade 5 polycontrast filter ten 2-second exposures produce exactly the same shade of grey as one 20-second exposure. Ditto test strips of the sort where 1:1:2:4:8:16 ... second exposures are made as cardboard is used to progressively cover up the paper.

If the total exposure time gets to be greater than 45 seconds then reciprocity failure will begin to factor in and short exposures won't sum
in a linear fashion. At 45 seconds reciprocity failure is only just noticeable
in normal printing.

If you use a cold-light head this won't be the case unless you use a compensating timer [better known as an 'exposure integrator']. Even with a compensating timer errors will occur because the spectral sensitivity of the light sensor will not be the same as that of the paper: the spectrum of the light will change as the lamp warms up and a non-spectrally-matched sensor will not track the response of the paper.

[Mr_Rocketkiller]

Is there anyone else out there who has made or is still making this mistake, I need moral support by knowing you at least exist !

Chalk one up for stupidity on me! My only excuse is I just started in a darkroom class about a month ago, and we were taught to use multiple exposures for test strips. Now I see why my test strips were always slightly off...

[Ray Heath]

Just a simple observation and a question. If I tested printing times and the result was 7 three second exposures, why would I want to make the print another way?

Or another way, if you make a test (experiment) and it gives you a result you want why would you change it when you make the full print?

It does not make sense to test one way and print another.

beause Joe, 7x3sec is harder to control than 1x21sec, ie once you start the exposure you'll lose count of how many 3secs you've done

it is correct, and easily demonstrable, that 7x3 is a lot shorter than 1x21, my procedure in such a situation is to redo the test strip as say 15+5+5, so if the 'correct' exposure is actually something like 18 the new test will soon prove it, then 1x18 is much more accurate

don't worry about wasting paper on test strips, better to waste strips than waste whole sheets, do as many tests as you need to be confident of a good result

a further consideration si not to change aperture to alter time, because when enlarging it's more important to have the lens stopped down to the middle of it's aperture range than it is to keep to a particular range of times