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01-20-2013, 11:46 PM   #1
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Capturing reds on digital

I was in the shower (where I do all my brilliant thinking) and it occured to me that a digital sensor captures IR as well as visible light, but a filter is used to remove the IR light. As well as that, I have noticed people saying that quality film captures reds much better than digital. So my point is, I was wondering what if the filter is part of the reason for that, and would it be possible to change the filter to increase the spectrum of red reaching the sensor?

Just thinking out loud and seeking opinions =) Won't be offering my K-5 up for this mod lol

01-21-2013, 06:16 PM   #2
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I don't have anything to contribute to this thread, I'm just trying to learn more about properly capturing reds -- mine tend to be oversaturated. So I'll be interested in others' expertise in this regard.
01-22-2013, 10:20 AM   #3
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QuoteOriginally posted by OrchidJulie Quote
I don't have anything to contribute to this thread, I'm just trying to learn more about properly capturing reds -- mine tend to be oversaturated. So I'll be interested in others' expertise in this regard.
Oversaturated reds is a problem with digital sensors. The red channel tends to clip, especially in bright sunshine conditions. Two possible approaches: 1. dial down your exposure until the red channel no longer clips. 2. Shoot raw, adjust the red channel in post-processing.

Also, it you have your camera set to 'vibrant', change it to 'natural'.
01-22-2013, 12:48 PM   #4
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Agree with everything MPrince said. I learned this the hard way with my K100D, now with the K-30. I haven't seen any other way, at least with Sony sensors. I think those Fuji sensors with 2 types of photosites of different sensitivities were supposed to be the best for reds.

01-22-2013, 01:39 PM   #5
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Im also mostly posting to subscribe to the thread, so I can read answers.
What I noticed with reds is that white balance and "camera calibration" play a huge role. I sometimes play with the hue of the red (and purple, violet) just to make the red on the photo seem like the red I remember from being there. Digital sensors still have room to improve
01-22-2013, 06:45 PM   #6
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QuoteOriginally posted by MPrince Quote
Oversaturated reds is a problem with digital sensors. The red channel tends to clip, especially in bright sunshine conditions. Two possible approaches: 1. dial down your exposure until the red channel no longer clips. 2. Shoot raw, adjust the red channel in post-processing.

Also, it you have your camera set to 'vibrant', change it to 'natural'.
Thanks. The default image setting on the K-r is "bright", and I noticed very early on that a lot of color (not only the reds) was oversaturated so I changed it to "natural". That helped quite a bit. Now I just have to practice and experiment, I suppose.

My first "exposure" (no pun intended) to this red saturation stuff was at work, where I use a D80 (I know, I know, but it's the company camera, I'm stuck with it) for various and sundry company purposes. Some of the subjects (flowers) are very, very red. I was running into the saturation issues there, and not always under bright daylight, either. Bracket city, for those. Will have to adjust and bracket on the K-r, too.
01-22-2013, 06:50 PM   #7
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QuoteOriginally posted by SteveB Quote
Agree with everything MPrince said. I learned this the hard way with my K100D, now with the K-30. I haven't seen any other way, at least with Sony sensors. I think those Fuji sensors with 2 types of photosites of different sensitivities were supposed to be the best for reds.
I feel better, knowing I'm not the only one puzzling with this. When 'togs with a lot more experience than I have acknowledge that it's an issue, I feel just slightly less of a noob. Just slightly!

Thanks for sharing your expertise, it's much appreciated!
01-22-2013, 06:53 PM   #8
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QuoteOriginally posted by Na Horuk Quote
Im also mostly posting to subscribe to the thread, so I can read answers.
What I noticed with reds is that white balance and "camera calibration" play a huge role. I sometimes play with the hue of the red (and purple, violet) just to make the red on the photo seem like the red I remember from being there. Digital sensors still have room to improve
Do you set your WB for each situation? I've generally allowed the K-r to do it "auto", but mostly that's because I've not been shooting in any unusual lighting conditions. Not yet, anyway.

01-22-2013, 07:32 PM   #9
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QuoteOriginally posted by OrchidJulie Quote
I don't have anything to contribute to this thread, I'm just trying to learn more about properly capturing reds -- mine tend to be oversaturated. So I'll be interested in others' expertise in this regard.
https://www.pentaxforums.com/forums/photographic-technique/190276-shooting-red-roses-2.html
01-23-2013, 04:24 AM   #10
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Thanks! That is definitely useful, much appreciated.
01-23-2013, 10:50 AM   #11
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The sensor doesn't do color directly. Instead, there's a filter directly over each pixel that makes that pixel red, green or blue. The filter is called a Bayer filter, not the aspirin but a Kodak scientist. His system has twice as many green filters as red or blue, for good reasons.

Now the camera's meter doesn't do color either (I believe high-end cameras of other brands do, but not Pentax). So the meter can be fooled by subjects with strong reds or blues and not much bright green to balance them out. The meter just sees light, comes up with an exposure and reds or blues end up overexposed. The classic case is a red rose. You carefully frame one bloom against a nice background, make sure the focus is right, choose a wide aperture, but forget about the dark green leaves. They trick the meter into the wrong setting, and you have a red blob photo. The error is usually greater than something you can recover even by shooting in RAW.

Add in white balance errors and flower photos can be disappointing, though this is something that using RAW can fix. The presets for daylight or shade can help JPG shooters.

It's one use for a spot meter - put the spot meter on the flower and it should be right for that flower. Fill flash can help by lighting up the greens but the matrix metering might still be wrong to start with. A concrete sidewalk can be used as a gray card and maybe even help with white balance if it is really gray, not mossy.
01-23-2013, 11:14 AM   #12
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QuoteOriginally posted by OrchidJulie Quote
Do you set your WB for each situation? I've generally allowed the K-r to do it "auto", but mostly that's because I've not been shooting in any unusual lighting conditions. Not yet, anyway.
I usually shoot auto WB, but since I shoot raw I can always adjust WB in post. I usually adjust WB if there are red objects or any people in the photo, to make those look normal.
But general landscapes or other images, I shoot auto WB or even CTE. Depends on what I want to accomplish.
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