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  1. #71
    RalphLambrecht's Avatar
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    By the way:

    The latest update of the spreadsheet, including very detailed instructions are now available.

    You'll find it here:

    http://www.waybeyondmonochrome.com/WBM2/Library.html

    and here:

    http://www.darkroomagic.com/DarkroomMagic/Darkroom.html

    The spreadsheet is now fully compatible with 21 and 31-step Stouffers. The instructions could use another English edit, but that would have delayed posting by another week. I hope it helps and you will report back with any issues you may have, so, I can improve it for future use.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  2. #72

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    I can't wait to get started. Thanks for the book and the reply.

    Charles

  3. #73
    PeterB's Avatar
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    Thank you for providing these instructions and Excel Worksheet Ralph.

    page 3/8 of the pdf says "Film has a different sensitivity to different wavelengths of light. Therefore, select a light source with a color temperature representative of your typical subject matter and setup."

    How do I measure the colour temperature of my light box upon which I will place the Stouffer step wedge ? Can I do this with a digital camera ? I'd like to ensure it is close to daylight.

    regards
    Peter

  4. #74
    RalphLambrecht's Avatar
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    How about a window?
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  5. #75
    PeterB's Avatar
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    Lol ! I guess I had incorrectly assumed that wouldn't give me diffuse light but if all the background terrain is out of focus then of course it will be diffuse. Then I also thought it wouldn't necessarily be at the right colour temperature because unless it was pointing straight up it would pass light reflecting from the surrounding terrain. OK so perhaps if I find a window with a view of a landscape plus blue sky with some puffy clouds thrown in for good measure it should be perfect.

  6. #76
    RalphLambrecht's Avatar
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    Quote Originally Posted by PeterB View Post
    ... Then I also thought it wouldn't necessarily be at the right colour temperature because unless it was pointing straight up it would pass light reflecting from the surrounding terrain. ...
    Peter

    That will be close enough. You want some of the surrounding terrain. Just the sky alone would be too high of a color temperature. Avoid early morning and late afternoon. You can also get some daylight bulbs for you light table, but I would not go through that expense.
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  7. #77
    PeterB's Avatar
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    Hi Ralph,
    the window didn't work ! Initially because the 'best' window position only let in afternoon sun which gave too much flare for my lens (yes I could have blocked that direct light into the lens but too much hassle again). The other problem is that with my lens it was impossibly difficult to get diffuse even light because the background wasn't sufficiently out of focus. So I then got a pane of glass from a photo frame and positioned it in a perfect place looking out to some trees, blue sky and a grey wooden fence, only to have the same problem with the background being too in focus. The other problem I then encountered was clouds moving into view changing the exposure levels !

    Can you comment on my next plan which is to get a piece of bright white cardboard and use that as a backdrop reflecting direct sunlight through a pane of glass about a few metres away upon which I have taped the transmission step. The white card should be neutral (i.e. have no colour cast) (excluding effects of any optical brighteners fluorescing). I would then set my camera exposure to a grey card sitting in the same sunlight, or even use a hand held light meter to get the incident light level.
    regards
    Peter

  8. #78
    RalphLambrecht's Avatar
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    Peter

    I thought it was obvious not to photograph directly into the sun, my mistake.

    Quote Originally Posted by PeterB View Post
    ... the window didn't work ! Initially because the 'best' window position only let in afternoon sun which gave too much flare for my lens ...
    What is wrong with that window in the morning?
    Regards

    Ralph W. Lambrecht
    www.darkroomagic.comrorrlambrec@ymail.com[/URL]
    www.waybeyondmonochrome.com

  9. #79
    PeterB's Avatar
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    Quote Originally Posted by RalphLambrecht View Post
    I thought it was obvious not to photograph directly into the sun, my mistake.
    I take responsibility ! It wasn't directly into the sun, the lens seems rather susceptible to flare so direct sunlight falling on it (but the sun itself not in the frame) is enough to noticeably reduce the contrast. I am using a Mamiya C330 with 80mm lens. I really need to get a lens hood as they are more subject to flare than the newer super multi coated lenses.

    Quote Originally Posted by RalphLambrecht View Post
    What is wrong with that window in the morning?
    I touched upon this when I described how moving my portable pane of glass didn't work either. When I said the background wasn't sufficiently out of focus what I also meant to write was that the background has different colours throughout it and causes some of the Tx steps to be illuminated with light from the blue sky, others from some green trees and others from buildings or fences . None of those light sources are neutral enough in colour to preserve the original colour temperature of the direct sun which is about 5500K.

    That is when I came up with the idea of using a white piece of card or paper to reflect direct sunlight back through a pane of glass a couple of metres away to which I affix the Tx step. I would ensure the white is behind the Tx step when viewed through the camera. Even if you still think I should use the natural environment can you comment on my idea 'cause in my mind it is superior to using some typical scene out of a window.

    Rgds
    Peter.

  10. #80
    Lee L's Avatar
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    To assure an even background for the step wedge, it's easiest to have a sheet of translucent perspex, opal glass, or a diffusion theatre gel behind the wedge. Backing with a clear piece of material (or nothing) will always produce the problems you're encountering and create an uneven background for the step tablet unless you have a very evenly lit uniform surface behind it. Make sure no direct shadows fall on the back of the diffusion material you use, as that will cause local 'density' differences.

    To avoid flare, mask off the area around the step wedge + diffusion material with darker material, perhaps a larger piece of foamcore, and use the lens hood you mentioned. You could also use a 5000K fluorescent lamp in a clamp lamp reflector behind such a set up to make something consistent and usable at any time of day or night.

    Lee



 

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