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Thread: The BTZS Paper Test, Do I compensate for Ilford filters?

  1. #1

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    The BTZS Paper Test, Do I compensate for Ilford filters?

    Bought myself a 4x5 21-step tablet and re-read the chapter in BTZS for how to do the paper test. My initial goal was to see the effects of the grades by eye - I wasn't initially going to worry too much about graphing them. This was to get an idea of how Ilford Coldtone differs from neutral but I plan on testing ADOX paper next (once I have some).

    Anyways, couple deviations I have to content with - I don't have the bellows extension for my D2 for my 150mm lens. I mostly print with my 135mm. Book indicates 150mm is best, but that would mean I'd have to print on 8x10. Instead I was thinking of using my 135mm for now which lets me print 1:1 (4x5) so I can save paper.

    Second, I use Ilford filters. The book is a bit vague here. It says to get the correct exposure with no filters used. But then it says NOT to adjust the exposure when using filters. But I know filters 4 on up normally require double the exposure. Should I compensate for this?

    Any other suggestions on carrying out this test?

  2. #2

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    Re: The BTZS Paper Test, Do I compensate for Ilford filters?

    I find it useful to contact print the straight 21 step tablets next to each other if I want a visual difference between films. Saves paper and seeing the shifts next to each other is easier than with the 4x5 tablet. The 4x5 is much easier to print and for film testing.

    You should not need to adjust the times for the contrasty filters. The paper scale is less than the range of the step wedge. A grade -1 will use about 1.8 density range, grade 5 will be about .6 and the tablet covers 3.0. Seeing the shift between them all is informative. You will need to adjust your exposure so that both extremes work.

    I trust the results from contact printing more than projection because of falloff from the lens and the light source (condensers and diffusion). If you have a meter that reads in 1/10ths of a stop or better it's informative to see how uneven things are by measuring on the baseboard. This will tell you if your 135mm lens is going to work. You can minimize falloff effects on the test by reading as close to the center of the target as possible when using the 4x5 target. Just remember that the falloff will be magnified (plus or minus) based on the contrast. So more effect on the higher grades.

    If you don't have the bellows you can print on strips from 8x10 with just the central portion of your wedge. That will save paper.

    Test both contact and projection to see the differences.

  3. #3

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    Re: The BTZS Paper Test, Do I compensate for Ilford filters?

    Ah good call on testing the fallout with a meter. I have a Sekonic 758 so I can see if it may be sensitive enough. I think I'd be fine with contact printing, I was just worried about the Callier Quotient. I have an Aristo Cold Light on my Omega D2 which is a diffusion head so that Quotient affects me less (with my D2 condensers it was pretty extreme) though not sure by how much.

    Initially I just kinda wanted to have some tests to get an idea of what the filters are actually doing, optionally between papers. Should help me figure out base exposure times but also which papers are contrastier than others (or so was my thought).

    I didn't quite follow this:

    Quote Originally Posted by Larry Gebhardt View Post
    You should not need to adjust the times for the contrasty filters. The paper scale is less than the range of the step wedge. A grade -1 will use about 1.8 density range, grade 5 will be about .6 and the tablet covers 3.0. Seeing the shift between them all is informative. You will need to adjust your exposure so that both extremes work.
    Basically you're saying I should NOT change the times from 00 to 5, but I SHOULD make sure the base exposure is enough to make sure I get useful results at 00 and 5? Perhaps it will become clear when I actually do the tests As a follow up though if I don't compensate for #4 and above, would I still compensate for them when printing? Ilford suggests if I'm say using a #2 filter but want to go to a #4 I need to double my exposure (either time or by opening the lens up 1 stop).

    If I understand how the strip is supposed to work - that would mean the results would be shifted by 2 steps (since each step is 1/2 stop) from where I ran the tests if I didn't change the time?

  4. #4
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    Re: The BTZS Paper Test, Do I compensate for Ilford filters?

    Can you post a link to this "BTZS Paper Test" in question to know what is to be tested.

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    Re: The BTZS Paper Test, Do I compensate for Ilford filters?

    You do adjust times when printing pictures of course. But do what Larry said for the tests.

    Contacts are scientifically better, because if you enlarge, your test is only "valid" for that lens and enlarger. I personally will do an enlargement test to illustrate the flare, as a demonstration for my typical setup, but I only do one or two of those. The rest of the tests (the family of filters) I would do by contact.

    When you make all the test contacts at the same exposure time, you can see how much more time you need for filter 4 and 5 because the white tone you want will be shifted from step to step. Just count steps and adjust your picture printing time a half stop for each step difference "between what you got and what you want".

  6. #6

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    Re: The BTZS Paper Test, Do I compensate for Ilford filters?

    Multigrade filters 4, 4.5 and 5 require twice the exposure than filters from 00 to 3.5, see here page two https://www.ilfordphoto.com/wp/wp-co...Multigrade.pdf.

    If you change the filter then light greys will remain the same, but as you increase the grade the shadows get darker and mids are more contrasty.

    So a recommended procedure is to adjust first light grey of the print and then increasing the grade until the shadows are dark enough for you.

    In this test all strips were exposed the same, 2 Lux during 20 seconds. The 2 lux were metered before placing the filters.

    Click image for larger version. 

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    From left you have the result with grades 0, 1, 2 and 3. You see that steps 12 are similar, but as grade increases the blacks are closer to that reference step 12.

    Then it comes grades 4 and 5, if exposure had been doubled then the grey in the step 9 would had been in the step 11, like with the other filters. (Grade 5 is upside down)

    At right you have an exposure with no filter, with 2 Lux going directly to the wedge... light grey has moved 2 or 3 steps up, telling that without a filter we should expose the half than with filters 00 to 3.5, and 1/4 than with filters 4 to 5, to have the same light grey in the same step.

    So if you make a calibrated plots then you may meter on the easel to know the exact density you will reach in any scene point.

    I had been teached by a retired very good printer that worked a lot in the wedding business. He was all day long printing. He told me that he usally nailed the prints (both BW and color) by accurately metering on the easel.

    He told me that in the same way we may perfectly expose an slide we also may expose paper perfectly.

    Of course a sound BW print may require a lot of work to refine the aesthetics, with burning, dodging, etc, etc. But with no test strip, just metering, we may predict the density in any spot.

    I found that an excellent reference to meter on the easel is using a Lux Meter app for the smartphone, that uses the ambient light sensor (for screen auto brightness).

    That sensor it's not scietifically good because it's very directional, but it works perfect on the easel. And the cost is LOL, if you have an smartphone.

  7. #7

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    Re: The BTZS Paper Test, Do I compensate for Ilford filters?

    It's important to note that the speed drop at G4 & up is much less on both Multigrade Classic FB & Cooltone FB - ISO P drops from 230 to 210 & 250 to 225 respectively.

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    Re: The BTZS Paper Test, Do I compensate for Ilford filters?

    Quote Originally Posted by m00dawg View Post
    Ah good call on testing the fallout with a meter. I have a Sekonic 758 so I can see if it may be sensitive enough. I think I'd be fine with contact printing, I was just worried about the Callier Quotient. I have an Aristo Cold Light on my Omega D2 which is a diffusion head so that Quotient affects me less (with my D2 condensers it was pretty extreme) though not sure by how much.

    Initially I just kinda wanted to have some tests to get an idea of what the filters are actually doing, optionally between papers. Should help me figure out base exposure times but also which papers are contrastier than others (or so was my thought).

    I didn't quite follow this:



    Basically you're saying I should NOT change the times from 00 to 5, but I SHOULD make sure the base exposure is enough to make sure I get useful results at 00 and 5? Perhaps it will become clear when I actually do the tests As a follow up though if I don't compensate for #4 and above, would I still compensate for them when printing? Ilford suggests if I'm say using a #2 filter but want to go to a #4 I need to double my exposure (either time or by opening the lens up 1 stop).

    If I understand how the strip is supposed to work - that would mean the results would be shifted by 2 steps (since each step is 1/2 stop) from where I ran the tests if I didn't change the time?


    I have a Sekonic 308 that gives 1/10th stops. I'd assume the 758 would be similar. Better yet is a Darkroom Automation meter that's accurate to .01 stop. It's a very useful tool at a decent price. You should be able to use it as a densitometer to read your step wedge for actual light levels at the paper to account for light falloff, but I haven't bothered with that yet so no idea if it works in practice.

    Yes, double the times when you print. Though in reality a simple doubling won't give the best print and you should probably make new test strips to get it just perfect.

  9. #9

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    Re: The BTZS Paper Test, Do I compensate for Ilford filters?

    Thanks everyone! I think that gives me enough info to give this a go! To recap sounds like I should start with contact printing (and maybe make a print via the enlarger just to see once I'm done to compare), keep the time the same once I get a proper (filterless) exposure.

    Excellent idea about using my phone as well! I use an incident meter app on the phone when I'm in a pinch and that indeed worked great (and did confirm there is indeed some falloff on the edges).

    Hopefully I can try this tonight. Probably will only have time to print tests but excited to see how this all works out! Thanks again folks!

  10. #10

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    Re: The BTZS Paper Test, Do I compensate for Ilford filters?

    Did my first tests last night! Here are the results! I think it went pretty well overall. The hinge on my (basically new, argh) PrintFile contact printer is broken and I haven't 3D printed a new one yet. This means a few of the tests I didn't have the glass down all the way so those may be a bit skewed.

    Even so, the affects of the filters are visible. A few steps are subtle but they're there. 4 and 5 are interesting. Perhaps the exposure was slightly off or the voltage to my cold light changed slightly but 5 does seem to have more contrast but shows a tad bit more exposure.

    Also does look like 4 and 5 do require a stop more exposure almost exactly so that was good to validate.

    My contact settings ended up being 135mm lens at f8 for 21" with no ND filter on the cold light which got made steps 21 and 20 white when using my filterless tests (which is what BTZS recommended). Usually when printing actual prints I have to use a ND filters (usually 2 or 3 stop) so base printing times are around 15-21".

    Max black for the no-filter test looks to be step 11. If I understand things correctly, that means minimum max black would be 5 stops less exposure at 21" (if printing a contact sheet with the same head height)? That makes some sense since I usually use my 3 stop ND filter and tend to be at f8 for 35mm and 120 and f11 or f16 for 4x5 at around the same same exposure time.
    Attached Thumbnails Attached Thumbnails cooltone-00.jpg   cooltone-no-filter.jpg   cooltone-0.jpg   cooltone-1.jpg  

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