Establishing Base Exposure

[Richard Lee]

I was wondering how those who practised f-stop printing went about establishing a base exposure for each negative.

Gene Nocon for example appeared to advocate doubling test print exposures i.e., 5, 10, 20, 40secs etc, in line with f-stop principles. Les McLean, on the other hand, seems to make his test prints on a linear timing basis using small increments; typically, three seconds. If I understand him correctly, it is from this, that he then makes a further test strip in f-stop increments.

I am the proud owner of an RH Designs f-stop timer wherein the default base exposure is set at ten seconds. Is it reasonable then, to always start from this point for all negatives and thereafter increasing the exposure by 1/4 of a stop for each test strip? I am aware, of course, that this default can be altered.

I tend to standardise on print size, so I'm guessing that I can do the same for my base exposures and stick with the RH default (provided the len's aperture remains constant).

Any words of wisdom would be greatly appreciated.

Regards,
Richard

[Leon Taylor]

I set my stopclock pro to about 2 seconds, then use the test-strip generator using 1/6 stop increments and concentrate on an important highlight area. If I feel the base should be between two steps I just adjust manually using the 1/12 or 1/24 option. My lens settings/enlarger/average neg density etc means my prints usually end up with a base somewhere around 5 seconds


If I'm split grading I'll do this for the soft grade base exposure, then use 1/4 increments when testing for the hard grade base.

[Dave]

I always make a near whole frame 1/4 stop test print on 10x8 R/C paper. Generally using 5 seconds at f22 as a base exposure, this gives me about a 3 stop range across the paper.

[Richard Lee]

Leon: Many thanks for your interesting and insightful reply. I am surprised however, that you appear to favour very short exposure times, and wonder if these hamper dodging & burning? While my Stopclock (purchased for a 'song' from the auction site, incidentally) doesn't have the 1/12 and 1/24 stop option; I suppose these are only required when short exposure times are preferred?

Dave: I'm also very grateful for your response - characteristically lucid as ever. I'm pleased to learn that your method for producing test strips is encouragingly similar to my own, except that I'm finding that the optimum strip is invariably on, or above, :wag: the higher end of the scale. Incidentally, how do your results on RC convert to FB paper (even when allowing for dry down)?

Best regards,
Richard

[Leon Taylor]

Leon: Many thanks for your interesting and insightful reply. I am surprised however, that you appear to favour very short exposure times, and wonder if these hamper dodging & burning? While my Stopclock (purchased for a 'song' from the auction site, incidentally) doesn't have the 1/12 and 1/24 stop option; I suppose these are only required when short exposure times are preferred?

Hi Richard

I find the 1/12 and 1/24 invaluable no matter how long the base exposure time - especially for fine control of highlight values. I reckon it is vital to get the highlight tone exactly correct to make prints shine so the more control available, the better.

As far as short base times hampering B&D control - I dont think it does really. I'm just used to it. I dont like using my lens at anything smaller than f11 so this limits the print times really. I do a lot of split grade printing though, and with the extra filter factor of the hard exposure, with which I tend to do most of my burning anyway, burn times are extended somewhat.

[RH Designs]

The earlier StopClock is rather different from the Professional model. You can set the base time in increments of 1/4 stop or 0.1 sec (up to 25.5 sec, 1 sec thereafter). It was designed based on Gene Nocon's book - the base exposure is important to get right, hence the ability to adjust time in small steps, but burning in is less critical. A quarter stop interval was good enough for Gene so I figured it was good enough for me too, although since then I've come to realise a finer interval is useful! Your base exposure is going to depend a lot on the enlarger type, negative density, size of print, etc so it's not really possible to give a definitive starting point. Leon and Dave must have brighter enlargers than mine - I usually need a base exposure in excess of ten seconds!

As others have said, make a test strip in 1/4 stop intervals which should get you into the ballpark. Judge the exposure only on the highlights. If your test strip is too dark, reduce exposure by one full stop and try again. If it's too light, increase the expsoure by one full stop. Once you have the approximate base expsoure on the test strip adjust the base exposure using the 0.1 sec controls so that the highlights look right. Usually you can interpolate the right exposure from adjacent strips on the test print.

At this point, if the shadows are too dark (blocked up) use a lower paper contrast grade, or if the shadows are too light (muddy print) choose a harder grade. You will probably have to adjust the exposure to maintain the highlight exposure if you change grade - ignore those who would tell you exposure for Multigrade paper is constant across paper grades. It isn't, except for a specific light grey tone.

Good luck :)

[Dave]

It’s quite perverse, invariably my test strip will indicate an exposure for the first work print of 10 seconds at f22 on a 10x8 R/C sheet, but if I skip the test strip, that isn’t the right exposure. Annoying that!

Changing paper types is a matter of knowing the characteristics of each of those that you use. There is a fixed relationship between exposure and contrast of each type, so a simple calculation will get you from, say, Kentmere VC Select to your super expensive FB special paper, well close enough to progress to the fine tuning stage.

I was going to say that the pivot point around which exposures swings when adjusting contrast is a grey highlight, but Richard (RH) put it so much better than I. It is something that confused me when I first started printing as I followed the oft repeated advice to expose for the highlights, and change the grade to control the shadows, but found that’s not quite right.

The use of the f-stop printing method is not limited to time adjustments, it also makes aperture, and enlargement changes easy to cope with.

[percepts]

I was going to say that the pivot point around which exposures swings when adjusting contrast is a grey highlight, but Richard (RH) put it so much better than I. It is something that confused me when I first started printing as I followed the oft repeated advice to expose for the highlights, and change the grade to control the shadows, but found that’s not quite right.

That depends on your filters. If using Ilford filters then it is right (ish) but with durst dichoic filters then it is a middle value.

The idea of setting print time for highlights and then adjusting contrast for shadows never made sense to me. The reason is because if you set film exposure for shadows and development for highlights then you should get a neg which prints close to grade 2. BUT with roll film you may have lots of different lighting ranges. They all get exposed for shadows so it will will be the highlight contrast which needs altering and not the shadow contrast. For that reason I think the Durst dichroic filtration is better because you can alter both time and contrast to get to where you want to be. With ilford filters, if you set the print time on highlight when the neg highlight density is high, there is no way you will get your shadow detail back by altering contrast. It will just block up because of excessive print time. But with durst dichroic filtration(Y+M) the mid pivot point doesn't lead to so much excessive print time and by altering print time in conjunction with contrast you can get to correct balance of time and contrast more easily IMO.
There is a way round this and that is to always develop negs a little soft and expose for the highlights and not the shadows which gives you room to play with shadow contrast having set print time for highlights.

[Leon Taylor]

why does there have to be so many ways to skin a rabbit :) ?

how does split grade printing fit in with your assessment Rob? I'm asking seriously ... I tend to split grade all my prints these days using ilford filters. I guess that way I am using time for both contrast and exposure so the best of both worlds? other than time and effort of course.

[RH Designs]

The idea of setting print time for highlights and then adjusting contrast for shadows never made sense to me. The reason is because if you set film exposure for shadows and development for highlights then you should get a neg which prints close to grade 2.

With film, development controls contrast; with paper, paper grade controls contrast. Exposing paper for the highlights is exactly equivalent to exposing film for the shadows - in both cases you're at the foot of the density curve of the material. Exposing paper based on the blacks never made sense to me!

With ilford filters, if you set the print time on highlight when the neg highlight density is high, there is no way you will get your shadow detail back by altering contrast. It will just block up because of excessive print time.

If it blocks up, your filter is too hard. If however your neg has bullet-proof highlights (usually caused by over development) then you may need to resort to other methods such as flashing to get detail into them. One of the problems with VC paper is that the contrast in the highlights is not very controllable (the paper curves will demonstrate that - the toe area doesn't vary very much with grade) and that's why some printers prefer graded papers.

Whether you split-print or use a single filter has no effect, apart from the fact that you can get intermediate grades using split-printing with Ilford filters.

[percepts]

Its not really relevant for split grade printing because we are are not looking for a print pivot point with split grade printing. Nor are you looking to get the neg to fit a grade 2 paper with zero or Y+M filtration.

My thinking is that if you have calibrated neg development to give a full 10 stops of subject range in the negative which prints onto a grade two paper, then most subjects will be short of that 10 stops range so you can happily expose for the highlights without blocking up the shadows. You just need to be careful of subjects with more than 10 stops range.

[percepts]

The pivot point for Ilford filters is around print density 0.3 which is approx a zone 7 print value. Perhaps a tad darker but certainly not as dark print value 6.
The pivot point for durst Y+M filters on my L1200 is around density 0.7 which is the same as an 18% grey card.

There is a siginificant difference which means using Ilfords filters makes little change to highlight contrast contrast when you change filter.
But with with my Durst using Y+M filtration, changing contrast makes a change to both highlight and shadow contrast. That needs to be offset with print time changes to retain correct highlight print density. But it does means you can change contrast at both ends and not just one end.
With Ilford filters a change in grade requires smaller change in print time because their is little change in highlight contrast.

I tested a vario head for my durst modular 70 years ago. The pivot point on that was 0.5 but for grade 4 and 5 it shifted significantly.
Dave uses a Vario head on his L1200 and I suspect it is better than the Modular 70 unit but I haven't tested it so don't know where the pivot point is.

Using split grade printing means you don't have to worry about the pivot point or Y+M values.

(p.s. all my tests were done on Ilford MGIV FB)

[Mike O'Pray]

I tested a vario head for my durst modular 70 years ago.

Rob I know that the thread asking you to mention the oldest thing in the darkroom excludes yourself but at your age I think an exception can be made:D:

Mike

[percepts]

Rob I know that the thread asking you to mention the oldest thing in the darkroom excludes yourself but at your age I think an exception can be made:D:

Mike

ho ho ho

modular-70

[Trevor Crone]

I think split grade printing is a very versatile method of printing allowing one to make very fine changes in contrast. As I've said before on this forum my method of SG printing is slightly different as I usually start at grade 2.5 (Ilford MG head). If the print looks soft I reduce the grade 2.5 exposure in increments of 10-20% and add the grade 5 exposure, usually in increments of 20% as most papers are slower in this region. Likewise if the print looks too contrasty I reduce the grade 2.5 exposure and increase the grade 0. I carry on this way until I get the look I'm after.

I try to 'peg' my negatives to print around grade 2.5 for this is the midway point in contrasts available to me using the MG head. Thereafter it is easy for me to slide up and down the contrast scale using this method if the negative should need adjusting in overall contrast.

This method works well for me as I ascertain a base exposure for grade 2.5 on my first work print before I feel the need to adjust contrast and any further adjustments to my printing plan. Areas of highlights, e.g. skies, usually receive additional exposure using just grade 0. Unless I need to locally add more contrast then I will add grade 5 to the burn.

[B&W Neil]

Trevor, that's very interesting as I usually start from grade 2.5 with the MG head as well. I don't do SG all the time but keep it up my sleeve for those occasions when I have a difficult negative.

Neil.

[Trevor Crone]

Trevor, that's very interesting as I usually start from grade 2.5 with the MG head as well. I don't do SG all the time but keep it up my sleeve for those occasions when I have a difficult negative.

Neil.

Neil, It does seem to make sense to start bang in the middle and take it from there. Like you I don't print every neg the SG way but it is such a versatile way of printing.

[Jon Butler]

We have been here on this subject many times.
I prefer to use fix grade 2/3 papers but have to print on MG these days because most papers are MG.
Even with MG paper I start with no filters as a base which is about equivalent to G 2.5 and sometimes may have to burn in with a lower or higher grade.

I said above sometimes as most of my prints are made with no filtration.
I do use spilt grade printing when printing other peoples negatives.

I aim and are obsessed to trying to make the perfect negatives that that print themselves.
If I sound like nutter I'm sorry but I am a negative freak.
JON.

[percepts]

to add to my earlier post:

If you always expose for the shadows you will get consistent negative density for the shadows. That negative density should always print for the same time to retain the shadow detail and separation. But that isn't what is usually taught which is to print for the highlights.

On roll film from subject to subject you will have different highlight negative densities according to subject contrast range and as we know you can't employ + or - development to cater for that on roll film as each subject is different. So you end up needing a different print time for the highlight of each negative. But how can that be correct if you have consistent shadow densities which should all have the same print time or thereabouts. Simply put, it can't.

But if you always expose negs for the highlight then you will get consistent highlight negative densities and providing the SBR is not too great your shadow separation and detail will be retained. It then becomes logical to use contrast adjustment to control shadow print density which also fits very well with Ilford filters as the speed point is on a highlight value of around zone 7. So if you expose negs for zone 7 then you will get remarkably consistent print times for every negative except the few that exceed a 10 stop subject range. For those longer range subjects revert to exposing for the shadows so that you don't get blocked shadows. You will get a neg more difficult to print but the detail will be in the neg.

[Stoo Batchelor]

I think split grade printing is a very versatile method of printing allowing one to make very fine changes in contrast. As I've said before on this forum my method of SG printing is slightly different as I usually start at grade 2.5 (Ilford MG head). If the print looks soft I reduce the grade 2.5 exposure in increments of 10-20% and add the grade 5 exposure, usually in increments of 20% as most papers are slower in this region. Likewise if the print looks too contrasty I reduce the grade 2.5 exposure and increase the grade 0. I carry on this way until I get the look I'm after.

I try to 'peg' my negatives to print around grade 2.5 for this is the midway point in contrasts available to me using the MG head. Thereafter it is easy for me to slide up and down the contrast scale using this method if the negative should need adjusting in overall contrast.

This method works well for me as I ascertain a base exposure for grade 2.5 on my first work print before I feel the need to adjust contrast and any further adjustments to my printing plan. Areas of highlights, e.g. skies, usually receive additional exposure using just grade 0. Unless I need to locally add more contrast then I will add grade 5 to the burn.

Very informative post Trevor. I have copied it for future reference as I am sure that it will come in very handy. A great thread all round from all involved.

Stoo

[Trevor Crone]

Very informative post Trevor. I have copied it for future reference as I am sure that it will come in very handy. A great thread all round from all involved.

Stoo

Stoo, with some experience with this method you can 'short circuit' it so to speak, for example with a negative that obviously requires more contrast I start my base exposure at grade 3/3.5 rather then the usual grade 2.5. After the first straight grade 3 print I start to reduce the grade 3 base exposure and start adding the grade 5 until I achieve the look I want. An example of this is my photograph of the Sea Stacks at Vik, Iceland. The grade 3 base exposure was 14.5 seconds + grade 5 base exposure of 3.5 seconds, total 18 seconds base exposure. The sky was burnt in at grade 0 for 14 seconds. It took me four prints to get to the final version although the others are quite acceptable.

[Stoo Batchelor]

Stoo, with some experience with this method you can 'short circuit' it so to speak, for example with a negative that obviously requires more contrast I start my base exposure at grade 3/3.5 rather then the usual grade 2.5. After the first straight grade 3 print I start to reduce the grade 3 base exposure and start adding the grade 5 until I achieve the look I want. An example of this is my photograph of the Sea Stacks at Vik, Iceland. The grade 3 base exposure was 14.5 seconds + grade 5 base exposure of 3.5 seconds, total 18 seconds base exposure. The sky was burnt in at grade 0 for 14 seconds. It took me four prints to get to the final version although the others are quite acceptable.

Again, I thank you Trevor.

Perfectly explained, and it even sounds like something even I could master. As you know, I have had very little success with the usual path of split grade printing using the 0 and 5 grades alone.

Copied and stored,

Cheers

Stoo