prints get lighter consecutivly

[res]

I recently started printing again and the first print looks the way I would expect. But each print after is much lighter when done for the same time (exposure and developer). I can't find what would cause this. I am using ansco 130 formula for developer, an acetic acid stop, and fotoformulary fixer(which is actually to old) and kentemere kentona paper. I don't do anything different after the first print and yet they come out lighter, like it was exposed half the time,this is very frustrating. One thing, I used amidol in the developer tray a couple weeks ago and before that but I don't see how that could do this. Anyone have any ideas? I only have a few minutes on the computer so I will look here tomorrow. Thanks.

 

[SuzanneR]

Is your darkroom cold? If the developer drops in temperature that may cause the print to be lighter. I haven't really used the asnco 130 formula so I may be wrong, but I did have this problem once with a different developer.

 

[Jim Noel]

If the tray was not cleaned extremely well there is a chance some amidol clung to the surface. It would then be absorbed by the fresh developer, but, I think, weaken rapidly. Since this is a powerful developer, it would account for the first print or two being more developed.
I keep separate trays for amidol, pyro developers, and conventional developers.

 

[David H. Bebbington]

Suzanne's tip is good - also, are you using an enlarger timer? Is it stable long-term? Might be worth checking with a stopwatch to see that a given setting really is the same every time.

 

[Donald Miller]

You failed to mention whether you are contact printing or enlarging...if you are enlarging, what type of light source? Cold lights are known to drift and will change as they are used unless you have some type of stabilization or light integration system to maintain the light output.

 

[pentaxuser]

In anticipation of your return to the computer, are you saying that without changing anything in terms of lens aperture, the setting on the timer etc you are getting a proper print then literally a few minutes at most later, a print that looks as if it was exposed at half the previous exposure?

If so it's a complete mystery to me and presumably rules out temperature change and cold light drift unless this is a sudden phenomenon as in one minute it's OK then the next it isn't.

Was the developer fresh? Here again I can imagine a point at which it exhausts quite quickly but not going from good to bad in the space of one print?

Is the second and subsequent prints progressively lighter or is each print after the first the same i.e. no progressive deterioration so print 2 is the same as print 3,4, etc

I take it that there is no chance that you haven't altered the aperture by one more stop? I ask this because on each subsequent neg I open up to max for fresh focusing then stop down again. In this procedure it is easy to stop down one more stop than intended.

pentaxuser

 

[res]

I managed to get back to the library tonight so in response its possible the tray had leftover amidol it is quite stained and I will clean it good tonight.
I am enlarging with a cold light and no regulator but my 2nd print was within 10 -20 minutes of the 1st(I didn't know it changed).
nothing in apurature or anything changed and the darkroom stays about the same as outsides temerature which is in the 70s and humid. I mixed the developer just a few days ago. thanks again Ill look back and try again tommorrow. thanks.

 

[srs5694]

I suggest an experiment to narrow down the cause: Expose two identical prints of the same negative, one immediately after the other -- within a minute or two of each other. Mark each one on the back so you can identify them later. Set one aside (in your paper safe) and develop the other. Wait a few minutes (10-20, as you say that a noticeable change occurs in that time), then expose a third identical print, mark its back, and develop it and the previously exposed but undeveloped print in quick succession (or at the same time).

If the change in brightness of the prints tracks with the time of exposure but development time has no effect, then you can be pretty sure that the cause is your enlarger's light source growing dimmer over time. If the change tracks with development time but not exposure time, then it's likely an effect of the developer.

Note, however, that exposed but undeveloped prints can change a bit over time; even with perfectly controlled development, the image can change a bit as the undeveloped print sits in the paper safe. This latent image change could throw a monkey wrench into the analysis, so I recommend using as short an interval as you're sure will produce an effect to avoid confounding that effect with the latent image changes. I've not done any careful tests of this matter, but I do recall noticing it once with color paper after a delay of about half an hour -- this delay created slightly more vibrant colors. I don't know if B&W paper would respond as quickly as this or what the effect would be.

 

[MurrayMinchin]

I am enlarging with a cold light and no regulator but my 2nd print was within 10 -20 minutes of the 1st

I'm pretty sure that's it; if you keep a cold light on while focusing, composing, and doing test strips it warms up quite a bit and produces more light than when it first gets turned on. If you then leave it turned off for ten minutes, it'll cool down and produce much less light.

It should be easy enough to test for by doing one print after focusing, etc, while the lamp is warm...one ten minutes later when it's cool... then a third after leaving the light turned on for a few minutes.

Good luck, and welcome aboard APUG

Murray

 

[Neil Miller]

I think Murray has got it - I use a cold light and leave it on all the time so the light output stabilises. Before this, iff I tried to make test strips with bursts of light they were meaningless because the light output varied so much at switch-on, so I now leave the light on constantly and use a swing-out safe-light filter over the lens. I now make test-strips by covering the whole of the paper with black card, swinging the filter out of the light path, and consecutively uncovering the paper.

You need to spend some time blocking all the light-spills so paper doesn't get any extra exposure when you are taking it out of the box, processing, etc, but you do get repeatable results. Maybe the life of the bulb is increased, too?

One drawback is that my RH Designs analyser/timer is now a bit OTT: I only use the ticking 'metronome' function - if I'd have known the problem before hand I would have got a cheap metronome and a whole lot of paper at the same price!

Regards,
Neil.

 

[MurrayMinchin]

One drawback is that my RH Designs analyser/timer is now a bit OTT: I only use the ticking 'metronome' function...

Hi there Neil,

I don't know if you knew this, but RH Designs does make a timer just for cold lights with a light sensor for reading the lamps output;

http://www.rhdesigns.co.uk/darkroom/html/stopclock_vario.html

Murray

 

[Neil Miller]

Thanks for that Murray!

I wish that it was available when I bought my unit, but it was a very long time ago and the sensor wasn't available then. I think it came out a long time after - maybe a couple of years - and I had got settled into another way of working by then.

Regards,
Neil.

 

[Neil Miller]

One thing about the compensating timer occurs to me after reading the link Murray posted - the compensation can only be applied during exposure, obviously - if the light output increases the timer speeds up, if it decreases the timer slows down. But if the light output fluctuates during the making of a test-strip, the timer has no way of knowing about this or compensating for it, so a print based on the test strip might still be lighter or darker than expected.

No big deal - who banks on the first print being bang-on anyway (I'm well pleased if I can get a decent representation after 3 attempts plus test strip) - but it does make me question the value of expensive gadgetry.

I know these devices suit some people (probably a lot of people, as there seems to be a big market for them) very well indeed, but there's a lot to be said for Michael A Smith's "outflanking the print" technique - even though I still make test-strips! I think (just my own, humble opinion) that the money saved by buying a metronome or other cheaper timing devices is put to a much better purpose by spending it on film or paper. Others may, and do, disagree.

Regards,
Neil

 

[photographs42]

........ But if the light output fluctuates during the making of a test-strip, the timer has no way of knowing about this or compensating for it, so a print based on the test strip might still be lighter or darker than expected........
Regards,
Neil

Why? :confused: Why is the test strip any different?
Jerome

 

[RH Designs]

if the light output fluctuates during the making of a test-strip, the timer has no way of knowing about this or compensating for it, so a print based on the test strip might still be lighter or darker than expected.

Not true, because a compensating timer is compensating during the making of the test strip as well. The number on the timer display can be interpreted as units of light volume rather than intensity - whenever you set say ten "seconds" you'll get the same exposure whatever the brightness of the lamp. The point of a compensating timer is exactly to make your print match the test strip!

The issue with exposure meters is they can't apply the same compensation unless you have a second sensor measuring the lamp brightness above the negative and compensating for any changes, which gets very complicated.

You can successfully use our Analyser with cold light, and many people do, simply by leaving the lamp on as long as possible. Just disable the lamp saver function which switches the lamp off after five minutes (to save tungsten bulbs) and leave the timer in "Focus" mode until just before you're ready to make the print. Provided the lamp has been on for many minutes and is thoroughly warm, and you don't spend more than a few seconds placing the paper on the easel and starting the exposure, the lamp brightness won't change that much.

 

[MurrayMinchin]

As I understand it, the timer considers a "second" as a given 'volume' of light...meaning that 1 "second" when cold will be very long, and 1 "second" when warmed up will be quite fast, but the paper will receive indenticle exposures.

This is the way it worked with my Zone VI compensating metronome, where it would go, "beeeeeeep.........beeeeeeep..........beeeeeeep" when cold and "beep...beep...beep" when warmed up, but the paper got the same exposure.

Check out the pdf version of the user manual in the technical section of RH Designs website...I believe it comes with a metronome too.

Murray

 

[MurrayMinchin]

D'OH!

I should take typing lessons to learn how to type faster...I see Richard cleared it all up while I was slowly pecking away...

Murray

 

[Neil Miller]

Think about it - the timer needs some time to speed-up or slow down once it determines that the light output is fluctuating. For optimum, repeatable results this requires the exposure time to be above a certain level, the enlarger to be warmed-up and the exposure to be made as soon as possible after measurements are taken (see Murray's link). If the cold head is flashing on-and-off (I think it does with the RH timer - it's been a long time since I used it in this mode) to make a series of test strips, then this is where the error sets in. Even if you move a card across the photo paper and keep the head on, the intervals are still quite small.

Richard Ross of RH Designs says: "...We do have customers successfully using the Analyser with cold light. The issue is short-term fluctuations - in other words if the light output changes between measurements, or between measuring and exposing, then the result may be incorrect. However, if you warm the tubes up well before starting to print these short term fluctuations are minimised..."

They can be minimised (not eliminated) and possibly ameliorated even more with some user-calibration of the unit, but as I'm pretty low-tech myself I prefer to use my eyes and count clicks. Each to his own.

Regards,
Neil.

 

[Neil Miller]

Richard - here's a (there was a url link here which no longer exists) to a previous posting of yours.

Regards,
Neil.

 

[Neil Miller]

Richard and Murray - I've re-read your posts and understand now what you mean by "units of light" and how - theoretically - this should ensure that the test strip chosen matches the print. My problems arose with the analyser pro - I don't have (and have no plans to get) the compensating variety.

However, I did use the Analyser Pro with both a cold light and a condensor head, and still found that the print varied from the chosen test strip. I even had small differences in test-strips made sequentially - just to test the repeatability of the meter. Even being talked-through the process by someone from RH Designs on the telephone (which was very courteous - was it you, Richard?) didn't help.

The most significant reason for this that I have been able to find is the theory (Fred Picker's?) that separate cumulative exposures are not equal to one long exposure of equal duration - I mean this to be taken in the light of my experience with the Analyser Pro and a condensor enlarger.

I do accept that a compensating timer can work around this, thanks to your explanation.

Regards,
Neil

 

[RH Designs]

Think about it - the timer needs some time to speed-up or slow down once it determines that the light output is fluctuating. For optimum, repeatable results this requires the exposure time to be above a certain level, the enlarger to be warmed-up and the exposure to be made as soon as possible after measurements are taken (see Murray's link). If the cold head is flashing on-and-off (I think it does with the RH timer - it's been a long time since I used it in this mode) to make a series of test strips, then this is where the error sets in. Even if you move a card across the photo paper and keep the head on, the intervals are still quite small.

Our compensating timer requires only a millisecond or two to respond so it's not going to introduce a significant error.

There is indeed a school of thought which suggests one long exposure does not equal the sum of several short ones but I have personally never found this to be an issue. Some enlargers take time to illuminate after power is applied and I expect this is the reason some people observe this phenomenon - for example if it takes half a second for the lamp to come on, five 10 second exposures would total 47.5 seconds, not 50. Ordinary bulb warm-up / cool-down time isn't an issue unless your test strip exposures are very short; to a large extent warm-up is balanced by cool-down.

If you find a difference between one single and several cumulative exposures, the simple answer is to make test prints rather than strips, with each print receiving the whole exposure. Our timers can operate in this mode if required.

 

[fschifano]

No offense to RH designs, but this whole thread makes me question the usefulness of cold light heads for the home darkroom worker. Incandescent bulbs have very quick response times, and modern VC materials are already calibrated to the light output of these devices. Go with a cold light and you need to start thinking about a couple of things. Is the color temperature of my florescent tube correct? Is it already warmed up and producing maximum light output, or will the light output fluctuate during exposure? In the end, does it really produce a result superior to what can be achieved with a standard diffusion type color or variable contrast light source powered by incandescent light? I'm inclined to think not. A cold light might be useful in a lab where high volume output is the norm. Once the tubes are warmed up, they are not likely to be off long enough to cool down; and the lower heat output, lower power consumption, and longer bulb life can be considerable advantages. For the home worker putting out maybe a few prints in an evening, a cold light is overkill offering no real advantage, and introducing a couple of considerations that must be addressed.

 

[MurrayMinchin]

Hmmm...maybe people aren't aware that a photocell gets installed into the light source, and that the timer is always compensating. A "20 second" exposure while cold will be idenitacle to a "20 second" exposure while warm...even if in real time there is about a 10 second difference between the two.

Murray

 

[Roger Hicks]

... this whole thread makes me question the usefulness of cold light heads for the home darkroom worker. Incandescent bulbs have very quick response times, and modern VC materials are already calibrated to the light output of these devices....

I'll drink to that. A lot of the mystique of cold lights is ritual and sympathetic magic, nothing to do with getting good prints with modern materials.

Cheers,

R.

 

[res]

well I tested and it was the fact that the light is less bright when cooled down even just after a few minutes. I just switched to a cold light last year and hadn't used it much untill now, I never knew this about cold light heads but its ok now that I know. Thanks for the responses.