Split grade printing contrast

[pentaxuser]

Thanks ercidan. I am now just curious as to what the explanation for your original observations in terms of contrast might be. You told us what you did and it posed a situation you did not expect which seems counter intuitive to what you thought should happen and I'd agree. You are rightly looking for an explanation and I am trying to harness a court of inquiry to ascertain an explanation which so far seems to be lacking. Indeed what useful information that has been given about your exposure system would seem to suggest that what you found you should not have found.

I hope that this doesn't "fizzle out" as some threads do with a kind of shoulder shrugging explanation that "it was just one of those things" It might be OK for Frank at the piano to say that when "its quarter to three, there's no one in the place 'cept you and me, so set 'em up Joe .... "

However your thread deserves more, even if it is the conclusion that something happened which remains unknown as the theory of VCCE means that unless there was an unknown gremlin which may forever remain a mystery, it should not have happened.

pentaxuser.

 

[MattKing]

Why would you expect the contrast settings to be perfectly linear, and centred exactly at an equivalent to grade 2.5?
If you are going to use split grade printing, it makes sense to do your initial "straight" print using split grade techniques.

 

[ericdan]

Thanks ercidan. I am now just curious as to what the explanation for your original observations in terms of contrast might be. You told us what you did and it posed a situation you did not expect which seems counter intuitive to what you thought should happen and I'd agree. You are rightly looking for an explanation and I am trying to harness a court of inquiry to ascertain an explanation which so far seems to be lacking. Indeed what useful information that has been given about your exposure system would seem to suggest that what you found you should not have found.

I hope that this doesn't "fizzle out" as some threads do with a kind of shoulder shrugging explanation that "it was just one of those things" It might be OK for Frank at the piano to say that when "its quarter to three, there's no one in the place 'cept you and me, so set 'em up Joe .... "

However your thread deserves more, even if it is the conclusion that something happened which remains unknown as the theory of VCCE means that unless there was an unknown gremlin which may forever remain a mystery, it should not have happened.

pentaxuser.

I agree. With constant exposure I should've arrived at a print that looks just like a straight 2.5 print.
Instead I get something that is slightly more contrasty.
Correct me if I am wrong, but given what I've learned in the thread so far, instead of a more contrasty print I should've gotten a less contrasty print with the 50/50 split.

what I mean is:
Perfect constant exposure: 50/50 split should look just like a 2.5 straight print
Not perfect constant exp due to faded filters: 50/50 split should look less contrasty since the grade 5 exposure is dimmer.

could it have anything to do with doing grade 0 first?
Doesn't it take a little while for papers to sensitize before they actually react to light?
I think that's why some people pre-flash their papers.
I wonder if I'd see the same results if I started with grade5 and then did grade 0.

 

[Svenedin]

I agree. With constant exposure I should've arrived at a print that looks just like a straight 2.5 print.
Instead I get something that is slightly more contrasty.
Correct me if I am wrong, but given what I've learned in the thread so far, instead of a more contrasty print I should've gotten a less contrasty print with the 50/50 split.

what I mean is:
Perfect constant exposure: 50/50 split should look just like a 2.5 straight print
Not perfect constant exp due to faded filters: 50/50 split should look less contrasty since the grade 5 exposure is dimmer.

could it have anything to do with doing grade 0 first?
Doesn't it take a little while for papers to sensitize before they actually react to light?
I think that's why some people pre-flash their papers.
I wonder if I'd see the same results if I started with grade5 and then did grade 0.

I don't have your exact enlarger but I do have a similar VCCE system on a different enlarger. I also have the RH Designs Analyser Pro and I spent a long time (and nearly driving myself mad) calibrating this device. I can tell you that your "constant exposure" isn't very constant if you actually go through a calibration process. It also varies (a lot) between papers.

 

[mfagan]

I have an LPL VCCE and did paper contrast tests described by Anchell in “The Variable Contrast Printing Manual.” I found, as Matt points out, that the 2.5 setting does not necessarily provide the equivalent contrast (“range number”) as a “2.5” graded paper (range number ~95). So, with Matt, I found that the VCCE settings do not provide a linear increase in contrast. That is, the 2.5 setting does not result in a range number (paper grade) that is the average of the grades that the 0 and 5 settings provide. They are settings, not calibrated paper grades. Now...I know I should be able to provide my test data here, but I have a note from home . I moved and have not yet unpacked everything. I will look diligently tomorrow, however.

 

[Svenedin]

I have an LPL VCCE and did paper contrast tests described by Anchell in “The Variable Contrast Printing Manual.” I found, as Matt points out, that the 2.5 setting does not necessarily provide the equivalent contrast (“range number”) as a “2.5” graded paper (range number ~95). So, with Matt, I found that the VCCE settings do not provide a linear increase in contrast. That is, the 2.5 setting does not result in a range number (paper grade) that is the average of the grades that the 0 and 5 settings provide. They are settings, not calibrated paper grades. Now...I know I should be able to provide my test data here, but I have a note from home . I moved and have not yet unpacked everything. I will look diligently tomorrow, however.

There is no 2.5 paper grade. i'm not actually that ancient but I learnt at school on graded paper only (I should mention to North American friends that "school" does not mean higher education in UK parlance except perhaps "medical school" which in my case is applicable). I do however use, from time to time Ilford fixed grade papers 2 or 3. Personally, I regard these as superior to MGIV but they are rather expensive and the only grades Ilford still make. What we make of as the actual filter grades is at best imprecise and at worst a bit meaningless.

 

[mfagan]

That’s why I put the 2.5 is in quotation marks. The equivalent range number would be approximately 95.

 

[Svenedin]

That’s why I put the 2.5 is in quotation marks. The equivalent range number would be approximately 95.

Fair enough. Very late here in the UK 0240 Zulu +1

 

[mfagan]

You’ve inspired me to look for my paper test records now (it’s only 2148 US east coast).

 

[cowanw]

The lever pulls all filters out of the way and gives white light.
At 0 the yellow filter will be completely in the way of the white light and the magenta filter will be completely out of the way.. Expose a piece of paper to your negative for a time such that you get an effect in the midtones.
Now expose a second piece of paper for the same time, at 5. You will find the same midtones will be much much darker.
Alternately have a look at the filter coverage at the 2.5 setting and see how much of each colour filter is in the way, if you can.
Your presumption assumes that the partial covering of the light by each filter at 2.5 is exactly half as actinic (or takes twice as much time) as each filter at total coverage, 0 and 5.
If you look on the insert that comes with Ilford papers the one colour setting table places 2.5 at 5m, 3 at 25M, 3.5 at 50M and so forth. Not a linear relationship.

 

[Ian C]

With respect to post 21:

“ . . . a very fine line exists for certain prints in terms of contrast and exposure which may not be achievable with the 0.5 grade steps afforded by Ilford filters.”

The following applies to the current version of the dyed-acetate Ilford Multigrade filters—not to dichroic filters, and not necessarily to dyed-acetate filters from other suppliers.

Any intermediate grade wanted can be obtained by using any two filters that span the desired grade. Figuring out how to do so requires constructing an appropriate model. It’s too much work for many. However, it’s easy to figure out how to arrive at 1/4-grade increments.

There are two cases:

1. Both filters from the same range.

Example 1. Suppose that you’ve made a 20-second grade-2.5 test print and a second one at grade 3 at the same aperture. Both prints have approximately the same density, but different contrast. You judge that grade 2.75 would look best. Give the next print half the required exposure at the low grade and half at the high grade to obtain the mid-point grade.

In this example you can expose for 10 seconds at grade 2.5 and 10 seconds at grade 3. This should result in a print of 20-second density and grade 2.75 contrast. This could also be done with the combination of grades 2 and 3.5.

2. Using one low-range and one high-range filter.

Example 2. You’ve made a 20-second grade 3.5 test print and a second 40-second print at grade 4. Both prints should be approximately of the same density, but differ in contrast. Suppose you want to achieve grade 3.75 contrast.

Give the next print 1/2 the required low-range exposure and 1/2 the required high-range exposure to obtain the desired midpoint grade

Expose for 10 seconds at grade 3.5 and for 20 seconds at grade 4. The density should match that of the test prints, but with approximately grade 3.75 contrast. This could also be done with the following pairs of filters: (3 and 4.5) and (2.5 and 5).

Although finer contrast increments can be obtained, most folks would find 1/4-grade increments sufficient and fairly easy to figure out

With respect to post #1:

Apparently the dichroic-filtered VC head is delivering more exposure to the high-contrast emulsion layer (or layers) at the grade 5 setting in the mixed-grade exposure than in the single exposure at the marked grade 2.5 setting. It’s a photo enlarger—not a sophisticated scientific instrument costing a huge amount. Such a variation in the light system of a photo enlarger is not unreasonable. It might be that the contrast grade delivered at the marked “grade 2.5” setting is closer to 2.2 – 2.3. Experimenting with various dial settings until the contrast matches that of the mixed-grade 0 and 5 print will show you the single dial setting required.