Test strips look different to full size print (RA-4)

Bumba · Dec 9, 2018

Hi,

When I scale up my test strips to full size prints, the full size is a little darker and any colour cast is stronger.
The filters, timing and enlarger hight are the same. I'm processing with a jobo drum and keep chemicals at 35 degrees for both. I'm using a smaller drum for the test strips which uses 40ml and the the full drum for the full print with 120ml. The processing times are the same.

Any idea why this is happening? I didnt think using more or less chemical volume would make a difference. Is this the cause or is it a problem when exposing.

Any help is appreciated and I hope this makes sense.

Thanks

foc · Dec 9, 2018

Are the test strips you are using, cut from the same paper batch as the full size prints?

Mick Fagan · Dec 9, 2018

You don't explain how you do your test prints. If they are, say: increments of 2.5 seconds each, in a strip one after the other, adding up to say: 15 seconds in total, then the time the enlarger lamp takes to get to full illumination for each mini exposure will usually mean your test print will be slightly lighter than the single exposure of your full sized print.

My take on test prints is to do increments in stops or partial stops, using my Jobo Variomat easel. Initially I would use full stops for the four exposures on a single sheet of 20cm x 25cm paper. This would invariably be 2.5 sec, 5 sec, 10 sec and 20 sec. I would pick the closest density to what I want and run a test in half or one quarter f/stops around that chosen test print. This way the enlarger lamp is on for the same time a full print will be on and any difference between a whole print as opposed to a test print, will see minimal to almost no change in density.

As an additional difference, as a colour print is made darker (more density) it will become more red. In colour printing you may have noted you only change filtration for two of the colours, Cyan is not used. Cyan/red is controlled (generally) by print density. The more exposure or density given, the more red, the less exposure the print will be more cyan.

If your filtration is completely on the money, then you will certainly see this cyan/red change easily. If your filtration is close, then you will still see the difference, but other colours may creep in.

As mentioned, greater accuracy will be obtained if your test paper and your final print are from the same batch, better still, from the same box or roll.

Mick.

Bumba · Dec 10, 2018

Yes, the paper is the same batch and chemicals are the same.

Thanks for the advice Mick. I think you might be right. I normally expose 5 mini sections on a test strip (1/4). When I made the full print I did have the bulb on for a while as I composed the image on the easel and checked the focus. I'll test it out and see if that's the cause.

I've also attached an image showing a section of test strip on the full print to show the difference.

Thanks for the help. I'll report back

koraks · Dec 10, 2018

I'm not sure your development is complete in the test strip. That's the first thing I'd rule out : make sure that test strips and full sheets get the same development.
For a buld-warmup difference, the difference between the print and the strip that you see is really quite large. I never see this kind of difference even though I always do strips at 2 sec increments which means the bulb has to warm up quite a few times. The difference is never even close to the difference I'm your prints which is something like half a stop or more.

Mainecoonmaniac · Dec 10, 2018

There are many factors that that causes a color shift that include paper batch, chemistry, and temperature. One often overlooked is print time. I usually change print density with F-stop instead of time.

Bumba · Dec 10, 2018

Thanks for the replies. Quick update, made a test strip today ranging from the bulb being used from cold to having been on for 5 minutes and warmed up. There was no difference between the bulb just being turned on and having been on for 5 minutes.

I make sure that they are developed for the same time. I allow for a longer drain time using a drum but use a shorter agitation time so in total both the test and full prints are in the developer for exactly the same time. The photo doesn't do the test strip much justice but it doesn't look underdeveloped in real life. The blacks look nice and deep.

Really stumped on this one. I'll have a think on it and get back to you all

Bumba · Dec 15, 2018

I'm back for some more advice. Been doing some more tests this week. Was wondering if my chemicals are a different temperatures each time I develop. I try and keep them at 35 degrees each time.

Can anyone give me any advice on the effect ot temperature on developer and prints? Say like a 1 degree difference either way

Thanks

koraks · Dec 15, 2018

RA4 isn't very temperature critical, particularly not to the extent you have shown here. FYI I use it at room temperature with ca 90 second development time. RA4 is essentially a develop-to-completion process. Variations in temperature may cause color shifts, but a one degree difference will likely result in no noticeable shift.
I remain with the hypothesis that your test strips aren't fully developed (I have ready your response to it but remain unconvinced). Why don't you develop the strips in the exact same way as the prints? Ie same tank, same amount of developer, etc. In case you're using the developer one shot and amount trying to economize: be my guest, but imo one shot development is unnecessarily wasteful. Just make something like a quart of developer and replenish it from time to time.

pentaxuser · Dec 15, 2018

I am puzzled. If you have eliminated all the variables( same paper, same chems, same processing time, temp etc between the test strips and final print then by definition, both the chosen strip and full print should look the same. I know this is stating the obvious but like Koraks and others I suspect all variables are not the same.

Just a long shot but in the first post you mention "scaling up " the test print to the full size one. If this means that you have the enlarger head higher for the full print than the test strip then this will change the light intensity and the same correct test strip exposure(e.g. 10 secs) at say 25cms will not be the same as 10 secs at 35cms.

Not trying to insult your intelligence but it is just as thought. I have no idea about the level of your experience but in my early days I'd have tested with a 4x5 sheet with the enlarger head at an appropriate height for 4x5, then used the correct time and then raised the enlarger head to accommodate a 8x10 without thinking of the consequences

Best of luck with your deductions as the the cause

pentaxuser

Mick Fagan · Dec 15, 2018

I don't believe any small variation, as you describe it, will make that much of a difference. I did drum developing of prints with RA4 and the prior to RA4 colour developing with differences of a few degrees C, with realistically, no real difference.

One thing I eventually did, was to practice a pseudo replenishment system. It worked quite well and I kept it up until I bought a paper processor. Essentially I would at least double the minimum amount of chemistry required, with larger drums I almost tripled the chemistry. If say, one required 50ml to develop a piece of paper, then I would use at least 100ml or most likely 150ml. At the end of the process I would remove 50ml then add enough new chemistry to get back to 150ml, or whatever my original amount was.

Mick.

Bumba · Jan 24, 2019

Thanks for all the continued advice everyone. I've been trying everything to figure bout what's causing the difference. I was convinced that the test strips were underdeveloped after koraks suggested it but it's not the case.

The only thing I could put this down to is that I use this homemade mask for my test strips so I can expose small areas at different colour filters. This is made of cardboard and for some reason that I can't understand this is causing the difference. It's more of a cyan cast when using it as when I texted at longer exposures the cast was still evident.

Bumba · Jan 24, 2019

This is the cardboard mask I use on my easel. I normally use it on test strips but used it on a full sheet for this one. It's made of cardboard and the black strips are tape to stop light getting through.

This is the difference caused by using the cardboard mask. The paper, chemicals, temperature, enlarger height, timer and filters were all kept exactly the same. I normally change filtration for each segment when using the mask but on this example I left them all the same so I could see the difference between the two prints.

I hope this makes sense and someone knows what's going on because I'm so confused as to why this is happening.

Sorry for the long post and thanks in advance

MattKing · Jan 24, 2019

Your mask is reflecting red light on to the paper, leading to a cyan cast.
Res Ipsa Loquitur

koraks · Jan 29, 2019

While the mask may very well explain the cyan shift, it does not explain the lack of density in the strips. I'd expect the opposite.

koraks · Jan 30, 2019

I'd solve the density issue first. Different exposures will induce color balance shifts, so dial in exposure first and then work on any color issues that remain.

monst · Jan 30, 2019

Have you tried building the exposure the same as the test print, like 4 x 3 second exposures instead of the one 12 second?

Photo Engineer · Jan 30, 2019

One thing I think that is missed here is that with color, it is always best to do tests by varying the aperture and not the time. So, keep time at 10 seconds and do an aperture series instead of a time series. This eliminates any possible reciprocity failure between layers.

PE

Bumba · Feb 5, 2019

Thanks for all the advice, it's really helped me out. I think I've solved my problem and as someone mentioned it was a combination of 2 things.

I solved the cyan shift by making a new mask out of black card. I also solved the density issue by increasing my time for development from 45 secs to 1 minute 10 secs. I could probably have used a shorter time but thought I should overdo it.

I reuse my chemicals but never normally increase my development time. Can anyone give me some advice on how much development time should be increased when reusing chemicals. I use them at 35°c btw.

Thanks

koraks · Feb 5, 2019

I can't really comment on that; I use a total volume of 500ml Fuji MP90 RA4 which I replenish at something like 10-20% per session with a session being a few to maybe 15-20 8×10's. I keep the development time constant at about 100 seconds at room temperature (15-20C). Prints come out the same all the time.

DREW WILEY · Feb 5, 2019

Attempting to replenish chemistry is probably not the best idea if you're having consistency problems. RA4 chem is cheap enough to use one-shot in drums. I mix it fresh for each work session.

Bumba · Feb 18, 2019

I'm back again and I think I've sorted the issue of the blue cast on my test strips but I'm still having a problem getting the correct drnside on my test strips. I normally reuse my chemicals but I mixed some new chemicals last weekend and I'm having the same problem of low density in my test strips.

This is my procedure for both:

Full size print: Place sheet of paper in the easel and exposure paper. Develop paper at 35°c for 45 seconds using a jobo processing drum with 120ml of chemicals.

Test strip: I use a 1/4 of a full sheet. Using a black card mask, I expose 5 different sections of the paper at different filter settings. I develop again at 35°c for 45 seconds, however, I use a smaller test strip sized jobo drum (modular part of the full drum) and use the appropriate amount of chemicals (40ml but I use 50ml).

I'm still finding a difference in density between the two even when exposed for the same time with the same filters.

What factors can affect density in an image? I can't seem to figure this one out. I tried extending the development time and that helped I think but I think I'm missing something else as surely the density should be the same if they are developed at the same time.

Thanks for any help as this is driving me mad haha

koraks · Feb 18, 2019

Tey developing them identically. So the test prints in the same drum with the same amount of chemistry as the full prints.

Bumba · Feb 25, 2019

I'm reusing my chemicals but I still get good looking results on a full size print. I have just mixed up some fresh and am getting the poor density with fresh too.

I developed 2 test strips in the full size drum with the same timings and amounts for a full print. One test strip using the mask and one with out. Both test strips had poor density leading me to believe that it's not the development or the mask causing the low density.

The only thing I can put it down to is the paper. Is there something about cutting paper or using smaller bits that causes density issues? It doesn't make aesen to me really but it is what it is. Test enlarger is at the same height too btw.

Finding this very strange

koraks · Feb 25, 2019

No, cutting paper will not influence the image characteristics. There must be another variable to your process that changes between test strips and full prints. But it is very, very strange indeed.

Test strips look different to full size print (RA-4)

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