I want to make a test neg, now what?

Discussion in 'B&W: Film, Paper, Chemistry' started by Eric Rose, Aug 19, 2007.

  1. Eric Rose

    Eric Rose Subscriber

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    I want to shot a pic of my Kodak step wedge thingy. So what should I do, meter the white and the black and determine the SBR from that and adjust the developing accordingly or meter just the Zone 3 part and adjust the exposure for that and develop at what is considered my normal iso.

    Film is cheap I can always do it both ways but I was wondering what you wold do. And no I don't have a Stoufer (sp) step wedge etc. I hope to make my own using the film I generally use, Efke PL 100.
     
  2. Donald Miller

    Donald Miller Member

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    Eric, If I were doing this I don't think that I would use the film as the basis for a self made step wedge...my reason is that the characteristic curve of the film comes into play. In other words while the steps of a step wedge from Stouffer or someone else is perfectly linear in terms of it's steps the film step wedge will not be linear especially on the toe or the shoulder regions of the film.

    If I were going to tailor my process along the lines of BTZS I would purchase a step wedge from Stouffer...they are like less than $10 US and when I had one, I would first contact print the wedge on the paper that I wanted to use and at the grade I wanted to use. From that the exposure scale of the paper can be determined...(by counting the number of steps between no exposure and maximum exposure)...next you could determine the density range your negative needs to be to match the paper. Normal contrast range would be SBR 7 (High EV minus Low EV plus 5) For expansion conditions (low contrast below SBR 7) you would arrive at an extended development time. For contraction conditions (high SBR above 7) you would diminish your development times...That is the simplified version of BTZS that I use.
     
  3. Eric Rose

    Eric Rose Subscriber

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    thanks Don.
     
  4. JeffD

    JeffD Member

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  5. Eric Rose

    Eric Rose Subscriber

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  6. Nick Zentena

    Nick Zentena Member

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    With out digging my Stoufer out isn't it on Ilford film? I thought my 4x5 step wedge was on Ilford film.

    If you order the Stoufer be carefull with their shipping price to Canada. Might be better to order from a dealer then direct unless they've changed shipping prices.
     
  7. vet173

    vet173 Member

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    Why? Test with a standard. Saves time and money in the long run.
     
  8. JeffD

    JeffD Member

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    I understand that, especially with the cost of a step wedge, but, believe me, it is money VERY well spent.

    I agree with Don Miller- if you photograph a linear step wedge, to make your own film step wedge, your step wedge is not going to be linear, but will be subject to a curve, and any conclusions derived from it cannot really be useful. This is assuming you are trying to make a transparency step-wedge from your negative, for the purpose of testing other films.

    However, you can get some useful info from photographing your printed wedge. If you *evenly* illuminate it, and meter the various patches, and photograph it, then you can check the resulting densities on your processed negative for film speed and development time.

    I would think that you could meter one of the darkest non black patches, and place this on zone 1 (give it 4 stops less exposure than your meter suggests). If, when you develop the film (using, say the vendors suggested time), and check the densities, this patch should have a density of .1 over film base + fog. If that is the case, then whatever EI you used to rate the film is pretty accurate. The .1 density number seems to be what is commonly accepted as the least amount of density over filmbase + fog that will yield a very slight off-black tone when printed.

    Hopefully you will have a patch, in the reflective wedge, that you meter to be 7 stops brighter than your zone 1 patch. This would be your "highlight", and you probably would want to test your development to obtain something like a 1.2 density over film base plus fog. This number seems to be what most people feel a grade #2 paper will print as just off white.

    The beauty of a stepwedge, and Donald Miller pointed out, is that you can contact print it on your chosen paper, with your chosen filtration (for VC paper), and can quickly see what kind of tonal scale you need to go for when developing. your Zone VIII exposure (7 stops over zone I) may need a little more or less density than the commonly accepted 1.2 over film base plus fog.

    Once you nail that down, you can test development to get a zone VII metered patch to equal that same density (+1 development), or to get a VI metered patch to equal that density (+2 development), etc.

    This method of photographing a printed reflective step wedge will undoubtedly seem crude, especially when viewed by BTZS afficianados, but, it is more than sufficient for most people. If you are using variable contrast paper, where you can adjust your contrast range up or down a little to correct, then you should be set.

    Hope this helps you, or maybe someone else who stumbles on this thread.
     
    Last edited by a moderator: Aug 21, 2007
  9. Eric Rose

    Eric Rose Subscriber

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    Thanks Jeff.