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Thread: converting slides to B&W

  1. #1

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    converting slides to B&W

    All,

    Apologies in advance if my question is somewhat stupid with an obvious answer to all the pros here.

    I remember reading somewhere that slides/chromes are generally more sensitive to incorrect exposure than for example B&W film, where the latter would have a larger exposure latitude than the former. (please correct me if am wrong, in which case you can disregard the questions below)

    1. If the paragraph above is true, does it then imply that the B&W film would have a greater tonality than a slide/chrome digitally converted into B&W?

    2. Now to the real question (the answer to which might have large effects on my choice of film): Will there be a noticeable difference in tonality and exposure latitude between a scanned slide/chrome converted into B&W and a scanned B&W neg?

    3. What are your recommendations? Do you regularly shoot slides and convert into B&W or is this the equivalent of a mortal sin?

    Many thanks in advance.
    /Magnus

  2. #2

    Re: converting slides to B&W

    Magnus,
    Apologies in advance if my question is somewhat stupid but
    what is "tonality"?

    Exposure of slides is more critical than exposure of negatives because there is no printing stage at which any compensating for slight exposure errors can be made. With colour or monochrome negatives something can be done at the printing stage to salvage the situation, provided the negative is only slightly over- or under- exposed.
    Colour slides are better slightly underexposed than overexposed but getting it just right is best and the latitude is small. Colour negatives are better slightly overexposed than underexposed -that leaves the printer a decently substantial density of negative to salvage something from.

    Exposure errors also cause colour casts in colour materials, which is not much of an issue with monochrome. If the colour cast is slight something can be done to improve this also at the printing stage but if it's there in a slide it's there and there it is.

    Copying i.e. re-photographing a slide or photographic print is not the same as photographing the subject in the first place. Brightly lit areas of the subject are imaged in the slide as thin areas with not much colour in them and in the print as pale areas ditto through which the backing paper shows. In the original subject the colour in these areas is just as saturated as anywhere else. Scanning digitised data into a computer presumably does not record the bright areas of the subject as "washed out" areas. Rather it would record data for the colour and data for the brightness. Photographing the original scene with a digital camera is equivalent to scanning it and should record more saturated colour in the bright areas than scanning a slide or print in which colour loss in these areas has already occurred.

    I guess this mightn't answer your question but I don't quite understand your question. Sorry.
    Last edited by Kendrick Pereira; 27-Jul-2006 at 12:25.

  3. #3

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    Re: converting slides to B&W

    Hi Magnus,

    Generally speaking, any conversion from analog to digital and vice versa (scanning included) introduces certain degree of degradation. Be it an image, a sound recording or anything else.

    Next, negative film in general, be it b&w, chromogenic or color, has a larger exposure latitude than any slide film. There may exceptions, but I don't know of any. If there really are, I'm sure somebody here will chime in.

    So, on to answering your questions:

    1. You don't say what would be the output of your B&W film - conventional print or digital print after scanning it. Judging by the way you formulated the question, I assume your b&w-converted slide woud be printed digitally. If you'd print the b&w conventionally, I would wager on it showing a very visible difference.

    2. If it were scanned as well, all bets would be off, depending on the skill factor of the operator. Again, in principle, any difference in analog should carry over and even be exaggerated after converting to digital, due to the inevitable losses introduced by the conversion process.

    Since slide films have narrower lattitude, they should come out of the scanner containing significantly less detail than any negative film. On the other hand, silver b&w emulsions (as opposed to chromogenic ones) are more difficult to scan than any regular color film because the scanner CCDs "see" them differently.

    Once scanned, the actual conversion from color to b&w should not introduce significant degradation, provided it is done competently.

    3. Photography is an art, not a religion. Therefore, everything's allowed, just like in love or wars. If it works for you, then there's no reason you shouldn't be doing it. For me, discovering what works and what doesn't and how does it work when it does and why not when it doesn't is the best part.

    But I bet some here will disagree and I'm sure we'll hear from them too. Which is great, because we'll both learn something from it. You'll find out the answers to your questions, and I'll get to test my understanding of the process...

  4. #4
    reellis67's Avatar
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    Re: converting slides to B&W

    1) That is true because you only have what is there to begin with, and if the scan does not capture %100 of that information, then you will end up with even less.

    2) If you are planning on scanning, I would suggest black and white print film. Others may disagree, but for me, having the most detail recorded would be the best option unless you have a specific need for a transparency.

    3) I use black and white negative film, print it, and scan the print if I want to display it online. As for sin, it's a personal choice, there is no right or wrong as long as you are doing what you want to do for a reason that makes sense to you.

    - Randy

  5. #5

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    Re: converting slides to B&W

    Quote Originally Posted by reellis67
    2) If you are planning on scanning, I would suggest black and white print film. Others may disagree, but for me, having the most detail recorded would be the best option unless you have a specific need for a transparency.
    Makes sense. But, on the other hand, starting with color film, either negative or transparency, would allow him to have both options and also to have more lattitude in conversion to b&w. E.g. play with filters, amplify certain colors or subdue the others, etc.

    Negative film would still be more flexible, I think, except that slides tend to have finer resolution.

    It also sounds like a good case for digital... Large format digital, of course, just so I don't test the tolerance limits here. ;-)

  6. #6

    Re: converting slides to B&W

    "Negative film would still be more flexible, I think, except that slides tend to have finer resolution."

    I have often heard this said but have yet to be convinced that it is so. I have recently been projecting our 35 mm slides and also have a project going to scan a large selection and have 4"x6" prints made for our kids' photo albums. Ditto with colour and b&w negatives. The slides do not seem to my eyes to have finer detail.

    By the way, Magnus are we talking of small slides [35mm or 2 1/4square] or large format transparencies?

  7. #7

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    Re: converting slides to B&W

    Quote Originally Posted by Kendrick Pereira
    "Negative film would still be more flexible, I think, except that slides tend to have finer resolution."

    I have often heard this said but have yet to be convinced that it is so. I have recently been projecting our 35 mm slides and also have a project going to scan a large selection and have 4"x6" prints made for our kids' photo albums. Ditto with colour and b&w negatives. The slides do not seem to my eyes to have finer detail.
    I'm not sure myself, that's why I said "I think". But on the other hand, I'm not sure you'd be able to see much of a difference on 4x6 either...

    Myself, I prefer to go digital for projects like that anyway.

    When I want to enjoy the process itself, I turn to 4x5.

  8. #8

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    Re: converting slides to B&W

    Thank you all for taking the time to answer.

    To clarify; I have no access to a wet darkroom so any prints would have to be made by way of digital.

    Shooting in colour (I prefer slides) would allow me to have a colour image which can be converted to B&W in Photoshop (added flexibility). The basic question is whether this method would generate B&W prints of lesser quality than those from a B&W neg when the differences in film characteristics are taken into consideration.

    Marko/reellis: I think you are hitting the nail on the head, at least as far as my limited knowledge goes.

    Kendrick: The question is more of a general one, and I assume there would be no difference in outcome for different formats. Please correct me if I am wrong.

    Marko: I agree this is a good case for digital (LF of course) as the final image would have been reproduced the least amount of times. There are of course other factors that detract from the digital systems that are currently available (price, resolution, iso, noise etc.)

    /Magnus

  9. #9

    Re: converting slides to B&W

    Most of the latitude you get from either B&W or color negative film comes from the fact that the film captures a much wider dynamic range than you can possibly put on photographic paper.

  10. #10

    Re: converting slides to B&W

    Magnus: I was just wondering if the comparison was between results obtained by scanning, say, 35mm colour slides and 4"x5" b&w negatives. I think the latter could be expected to deliver better image quality when you print from your computer. If your only concern is exposure latitude I think you are right about the same principles applying the same way to different formats: but you also ask, "Do you regularly shoot slides and convert into B&W or is this the equivalent of a mortal sin?" Exposure latitude is not the only consideration which bears on this choice though of course it might be the only aspect you are inviting attention to here.

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