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  1. #11

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    I've seen the same in Ektar scans when underexposed. The shadows shift to purple. Didn't matter if I developed or a lab developed. I started shooting to make sure the shadows had enough exposure and I don't really see it often any more. Ektar can handle quite a bit of overexposure. This does bring up a subject I posted on quite a while back about the Ektar data sheet giving exposure settings for ISO 50 film, not it's box speed of 100. If you look at the recommended exposure settings for given lighting in the datasheet it's the same as Velvia 50. Things that make you go "Hmmmmmmmm".......



    Quote Originally Posted by jbl View Post
    Thanks for the help everyone. Some more data.... I've seen this with two rolls of Portra 400 I processed myself a couple of months apart with a different mixing of chemicals (same concentrate, just two batches of working solution). I've also seen this with a roll of Reala I shot back in July that was processed commercially at a decent lab (it was at a fairly good local camera store, not at a mini lab). I'm attaching a few examples of this.

    portra-1 is the example from August that I processed. portra-2 is the example from the other day that I processed. reala is the example from July that was commercially processed. Only one of these photos is any good :-).

    -jbl

    Attachment 46281
    Attachment 46282
    Attachment 46283

  2. #12

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    I just checked some of my Portra 400 scans and I see the same purple shift in dark, underexposed areas. It becomes more noticable when you boost the lower end of the tone curve to lighten the dark areas. I don't think it has anything to do with your processing, it's more a trait of the film when scanned. I can't say if the same thing would happen when using traditional printing techniques.

    Quote Originally Posted by Lamar View Post
    I've seen the same in Ektar scans when underexposed. The shadows shift to purple. Didn't matter if I developed or a lab developed. I started shooting to make sure the shadows had enough exposure and I don't really see it often any more. Ektar can handle quite a bit of overexposure. This does bring up a subject I posted on quite a while back about the Ektar data sheet giving exposure settings for ISO 50 film, not it's box speed of 100. If you look at the recommended exposure settings for given lighting in the datasheet it's the same as Velvia 50. Things that make you go "Hmmmmmmmm".......

  3. #13
    markbarendt's Avatar
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    Quote Originally Posted by Lamar View Post
    I just checked some of my Portra 400 scans and I see the same purple shift in dark, underexposed areas. It becomes more noticable when you boost the lower end of the tone curve to lighten the dark areas. I don't think it has anything to do with your processing, it's more a trait of the film when scanned. I can't say if the same thing would happen when using traditional printing techniques.
    A color exposure is actually made up of 3 separate exposures, one for each color layer.

    The layers don't always balance so to print we adjust color balance by adjusting the luminance of the layers separately.

    In a typical photo as long as you are printing from the straight line portion of all three layers you can do a fair job of balancing.

    The problem comes when we reach the toes. Since the layers don't always get balanced exposure we skew things to balance the mid tones and then the toes won't balance. The luminance on the toes don't balance at the same place the straight lines do so you start getting color casts in the shadows.
    Mark Barendt, Ignacio, CO

    "We do not see things the way they are. We see things the way we are." Anaïs Nin

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