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05-20-2015, 08:57 PM   #1
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Sensors. K-50 vs K-3. Any difference?

My question narrows down to the ability to render reds. My K-50 simply will not render reds - the deep, rose-red colors - with anything close to what I'd like. So, aside from having more MP, is the K-3's sensor more capable of color rendition?

05-20-2015, 09:14 PM   #2
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My K50 has trouble with this also. I keep meaning to drag out my K100D Super to see if it can render the reds.
05-20-2015, 09:16 PM   #3
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QuoteOriginally posted by Dewman Quote
My question narrows down to the ability to render reds. My K-50 simply will not render reds - the deep, rose-red colors - with anything close to what I'd like. So, aside from having more MP, is the K-3's sensor more capable of color rendition?
Have you adjusted your custom image settings? The default Pentax profiles tend to over-saturate reds. Shooting in RAW helps recover them, too.

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05-20-2015, 11:21 PM   #4
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I shoot RAW and find moving the red hue slightly towards orange when processing the RAW files (around +8 on the red hue slider in Lightroom) will make reds look more realistic (as other conversations on the forum also tend to agree on). Also as discussed in many other threads, digital cameras tend towards overexposure on the red channel well before the green and blue channels. I use the three channel histogram when reviewing images and where I deem red tones to be important, dial in enough -ve exposure compensation to ensure the red channel isn't burning out. The single luminescence histogram won't show a red channel only overexposure as it is an average of the three colour channels that it is displaying and often the single channel overexposure is masked by the averaging.

Red flowers and sun sets are two subjects where I've learnt to watch the red channel closely.

05-20-2015, 11:45 PM   #5
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QuoteOriginally posted by Dewman Quote
My question narrows down to the ability to render reds. My K-50 simply will not render reds - the deep, rose-red colors - with anything close to what I'd like. So, aside from having more MP, is the K-3's sensor more capable of color rendition?
This has nothing to do with the sensor but with how the sensor raw data are processed. Depending on JPG settings and especially the color profile (i.e. how raw data are translated to RGB values) you can get dramatically different results with the same Raw data.

When shooting JPG or Raw using the Pentax software you cannot change color profile settings but only fiddle with the JPG settings. In proper Raw development software (Raw Therapee, Lightroom) you can also use different DCP color profiles, even create your own if you have e.g. a Colorchecker24.
05-20-2015, 11:53 PM   #6
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To my understanding, Any "Bayer array sensor" (including K-3 and many camera's in the market) out of the box struggle to render deep red colored areas and for example produce a sharp rose petal!
You can find the reason in their sensor design!
A bit more info about the sensors: Understanding Digital Camera Sensors
05-21-2015, 02:55 AM   #7
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I don't think you'll find a lot of difference between Pentax sensors when it comes to reds. I try to under expose a little bit when shooting red, which seems to help and I shoot RAW, which helps a lot. I think using a setting other than Bright if shooting jpeg -- Natural or even Muted would be helpful. Bright (and some of the other jpeg settings) really bump the saturation, which can give unusual results sometimes.
05-21-2015, 05:54 AM   #8
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My K-3, like every other camera, also struggles with reds. However, I find it easier to recover and reconstruct the reds on images from my K-3 easier than I could on images from my K-30 - especially at low ISO settings. I don't know if it's because the K-3's sensor has lower noise, wider dynamic range, or if the exposure system has been tweaked.

05-21-2015, 06:09 AM   #9
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I might mention that I normally shoot JPEG in "Natural" on the custom settings, and in that setting, when shooting a deep rose-red, I reduce the saturation, kick the hue a little toward the blue side and reduce the high/low key adj. and also reduce the contrast. This seems to be the best I can manage, but it still leaves a lot to be desired. I've decided this is the best I can do with this particular camera and sensor. So.... this is to say I usually avoid shooting reds!

---------- Post added 05-21-15 at 07:17 AM ----------


Last edited by Dewman; 05-21-2015 at 06:18 AM.
05-21-2015, 06:45 AM - 1 Like   #10
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I have a k-50, shoot raw and use Lightroom mostly. To tame the reds, I use the Red channel in the tone curve. At the 255 point, I pull down that end of the straight line curve a bit. And, at the 0 point, i pull up on that end of the straight line. You may get by pulling down the 255 end of the curve/line and leaving the 0 end alone. You'll end up with a line with a slope that is less than 45 degrees, which lowers contrast and saturation. I make the tone curve adjustment before any other adjustments. You can tweak things a bit in the Hue, Saturation, and Luminosity tab.

Last edited by T Evergreen; 05-21-2015 at 06:53 AM.
05-21-2015, 06:50 AM   #11
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For deep reds you underexpose slightly.... and process with levels to even out the channels. A red flower on your porch, close to your computer will enable you to get a handle on it. Just shoot at different exposure levels and process until you get something you like. I seem to remember -.7 EV is what i settled on last time.
05-21-2015, 06:57 AM   #12
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Here's an example of adjusting the red channel in the tone curve as I described above:
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05-21-2015, 06:59 AM   #13
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Ha, ha, I have one of those too.... but I just have the result, not the before and after. I basically processed to bring out the veins in the petals, they were blasted in the original image I took.


Last edited by normhead; 05-21-2015 at 07:15 AM.
05-21-2015, 07:06 AM - 2 Likes   #14
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This screen shot also show the adjustment to the tone curve:
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05-23-2015, 03:36 AM   #15
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QuoteOriginally posted by T Evergreen Quote
I have a k-50, shoot raw and use Lightroom mostly. To tame the reds, I use the Red channel in the tone curve. At the 255 point, I pull down that end of the straight line curve a bit. And, at the 0 point, i pull up on that end of the straight line. You may get by pulling down the 255 end of the curve/line and leaving the 0 end alone. You'll end up with a line with a slope that is less than 45 degrees, which lowers contrast and saturation. I make the tone curve adjustment before any other adjustments. You can tweak things a bit in the Hue, Saturation, and Luminosity tab.
Interesting, I either wasn't aware or had forgotten that LR allows individual channel adjustment of the tone curve. In addition to the precautions/PP technique I mentioned in an earlier post in this thread, that's yet another spanner I can pull out of the toolbox to wrangle unruly reds. Thanks!
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