[RAART]

I thought that Pentax is really good with colors then on the last weekend I encounter problem with red color overexposing and loosing details. First I was thinking that I had spot metering but I didn't, after checking exif... I did not overexposed the picture I think and if, probably minimal but still thinking that exposure was right. I did not have problem with red colors usually but this red got me... To save the picture and just about curiosity I decided to create a virtual copy in the LR than from there I underexposed the copy for 1 stop and combined both of them in NIK HDR software. The image was ok, but none then less I am still wondering if it is only the Pentax who is plagued with this problems or all cameras have similar problem.

Does anyone else has occasionally this problem.

TBH I did not had this problem before, this is the first time even I shoot the red flowers before. Strange...



Here is the regular processed picture, from e where I was starting from...



and here is the stacked PP one...

---

Last edited by RAART; 06-16-2015 at 02:00 AM.

[Sorver]

I thought that Pentax is really good with colors then on the last weekend I encounter problem with red color overexposing and loosing details. First I was thinking that I had spot metering but I didn't, after checking exif... I did not overexposed the picture I think and if, probably minimal but still thinking that exposure was right. I did not have problem with red colors usually but this red got me... To save the picture and just about curiosity I decided to create a virtual copy in the LR than from there I underexposed the copy for 1 stop and combined both of them in NIK HDR software. The image was ok, but none then less I am still wondering if it is only the Pentax who is plagued with this problems or all cameras have similar problem.

Does anyone else has occasionally this problem.

TBH I did not had this problem before, this is the first time even I shoot the red flowers before. Strange...



Here is the regular processed picture, from e where I was starting from...



and here is the stacked PP one...

[

I only recently experienced this problem also with my k-3 and a red flower I will have to go back and see if I can find it I was ready to use the grey card to see if the metering was still behaving.

[narual]

This is a constant problem with digital cameras in general, I think, but both of my Pentax cameras seem more susceptible to it than my nikon was. Both red and magenta can cause it.

I mostly run into it with flowers on sunny days, and with bands and other staged events where the red lighting can cause it.

When I'm photographing in a garden (I visit botanic gardens now and then, and every couple years I have to photograph an event where people open up their gardens up to visitors), I turn on the RGB histogram view. That can help a lot - you'll see if red is blown out before you get home and try to process the shots. The regular histogram isn't useful in this situation because it weighs green much more heavily than red (and barely uses blue at all). Your green channel can be fine while red and blue aren't, and you won't see it unless you look at the RGB histogram. (I really wish you could choose just one color to show, or that you could get the RGB as an overlay on a full sized photo instead of the tiny one)

It's something to do with the camera trying to balance brightness to get an average of 18% grey, but the bayer sensor has twice as many green sites as red and blue, and it's more sensitive to green than to red, and red than to blue... so a closeup of a red flower on green is going to blow out the red because it thinks the scene is darker than it really is.

I've also read suggestions that an IR Cut filter can help a lot, as the sensor is still somewhat sensitive to near IR light just above where the human eye can see it.

Or just do it the easy way, which is how I handle most locations where I'm not 100% sure on the exposure anymore. Shoot in raw and take bracketed shots with either +2, -2, or both. You'll throw away a lot more shutter actuations, but you're covered for exposure problems and you can merge them for HDR if you need to recover both high and lowlights.

[biz-engineer]

I had the same problem, and it was significantly worse with the K-3 vs K-5. Solution was to expose (underexpose) for the red. Canon 7D also show this problem but to a lesser extent than Pentax K-3. What's surprising to me is that it seems that the K-3 does not take advantage of its 86K RGB sensor. With the 86K sensor, the camera exposure should detect this red pattern and expose accordingly.

[TER-OR]

There are a few threads about this on the forum. The CMOS sensors are "hot" for red. The solution seems to be to deliberately underexpose a bit, and of course shoot RAW. We'll see whether Sony or other sensor manufacturers addresses this in the future. Given their 16MP sensor had this issue, and so does the 24MP I wouldn't hold my breath.

[RAART]

I read all threads already but strange thing is that I did not had this problem before. I shoot already a plenty of red flowers and never had a problem as I was really careful with exposure. This is the first time I run into. Yes, I did have slightly overexposure when red color was dominant but very rare and not so drastic like this time. The funny thing is that it was overcast day without sun rays even peaking through the clouds. Just a giant soft-box, diffused light and I did not even expected a red to be blown out that way.

With K-5II I never run into this, nor with my old Nikon D300s... Too bad that I do not have Nikon or K-5II now just to compare how they are behave.

Maybe I should look for back-up body into Fuji or much better Sigma...

I could do a bracketed exposure but with flowers moving I do not think it is good idea, unless I do not have wind at all however fortunate me who lives 300m from Lake Ontario, there is always a breeze.

What was worried me is if the last update did something to it, as I did not had experienced this so drastic before. I guess this is just temporary paranoia...

That with IR filter might be a good idea as the sensors are more sensitive to broader spectrum but I was always thinking that each manufacturer placed proper filter into Bayer array and we do not have to play with additional filters here. My guess here is that Sony did not made good job on 24.3MPx sensors. Just wondering again how Fuji will behave in such condition as they have exact numbers for every channel (RGB) of pixels in one array. Sigma probably will be the best without any questioning here.

Will look further into and I might spend a money on Color Checker... or get a Sekonic lightmeter with color checker included.

---------- Post added 06-16-15 at 09:47 AM ----------

Here are two screenshots where you will see that luminance adjustment in LR helped a lot but still...

Before any adjustments, everything on "0"



After luminance adjustment only...

[dcumpian]

My K-3 isn't as bad as my K-r was, but I always underexpose out of habit when there is a lot of red/magenta in a shot.

Regards,
Dan

[DoctorX]

I have this problem on my K-3 with a particular species of red flower but not all red flowers. I wonder if the flower is reflecting light outside the visible spectrum that is messing with the sensor. Just a guess. Does not appear to be a problem with my Nikon coolpix or iPhone,

[wkraus]

Here are two screenshots where you will see that luminance adjustment in LR helped a lot but still...

Before any adjustments, everything on "0"

After luminance adjustment only...

Interesting... the unadjusted histogram shows the red channel is not really blown. There are several factors involved. Shooting raw, as already mentioned, is mandatory to properly handle these colours. Next, which colour profile are you using? sRGB with its small gamut will make a mess out of these saturated colours. ProPhoto RGB will be able to separate even highly saturated colours (but again you will not be able to print the output as no printer can reproduce such a wide gamut). Finally, the details may be there but your monitor may not be able to display them--most monitors are not. I have access to a wide gamut display in my office and with highly saturated colours there is a lot of difference as compared to my MacBook Pro retina display.
FWIW, I downloaded your unadjusted sceenshots and the reds that are there (internally in Lightroom at least) are all blown. AFAIK, Lightroom uses ProPhoto RGB internally.

[stevebrot]

I am still wondering if it is only the Pentax who is plagued with this problems or all cameras have similar problem.

All digital cameras have problems with intense true reds and yellows. It is a characteristic of electronic photodetectors in general, regardless of sensor type (CMOS, CCD, or what have you).* The detector linearity varies by wavelength and its output is more difficult to manage at the warm end of the spectrum. As a result, both red and yellow tend to "block up" prematurely and lack smooth tonal gradation.


Steve

* My K10D (CCD sensor) was terrible with yellows and worse with reds and my K-3 (CMOS sensor) carries on the tradition.

[rawr]

There have been several threads that highlight other potential factors in troublesome reds that you may like to explore:

- JPEG encoding schemes and compression levels can impact red rendering, so those may be some settings to experiment with;

- the settings for noise reduction can impact red rendering. For the K-3 in particular, reduce the level of chroma noise NR, and red detail (cf the Imaging Resource test charts) suddenly comes back. LR usually sets the chroma noise NR default too high for the K-3, even for base ISO.

Using other RAW software can also sometimes have interesting impacts on red and other colours, and so experimenting with other RAW tools can be useful - Pentax Digital Camera Utility springs to mind as a good option. Every RAW processor that I have ever used seems to have a different opinion about reds.

[RAART]

Interesting... the unadjusted histogram shows the red channel is not really blown. There are several factors involved. Shooting raw, as already mentioned, is mandatory to properly handle these colours. Next, which colour profile are you using? sRGB with its small gamut will make a mess out of these saturated colours. ProPhoto RGB will be able to separate even highly saturated colours (but again you will not be able to print the output as no printer can reproduce such a wide gamut). Finally, the details may be there but your monitor may not be able to display them--most monitors are not. I have access to a wide gamut display in my office and with highly saturated colours there is a lot of difference as compared to my MacBook Pro retina display.
FWIW, I downloaded your unadjusted sceenshots and the reds that are there (internally in Lightroom at least) are all blown. AFAIK, Lightroom uses ProPhoto RGB internally.

I checked and LR has ProPhoto RGB set if the file is handled in external editor Photoshop CC and sRGB if in some other external editor. I don't think that you can change color space in LR at all, speak must be ProPhotoRGB as this is the default. Maybe it is my monitor but anyway I will replace it soon anyway but still... I have another RAW file untouched at all with same problem and the only thing that I do prior any editing is to change to "Embedded" profile under Camera Calibration, but that's it. I use always embedded profile as this gives me more accurate colors then Adobe Standard.

I uploaded this file here: https://drive.google.com/open?id=0B-iswHReGS-cbnJ2U2EtdWROMFU&authuser=0

You can play with it as I do not need it... you can also check the histogram on your computer.
Lens used here is FA100mm ƒ3.5

EDIT:

Here is the original file, posted at the beginning of the thread: https://drive.google.com/open?id=0B-iswHReGS-ceWwzNHFFbXlrTW8&authuser=0

Lens used here is DA50mm ƒ1.8

[Funsize]

Reds were pretty much the main reason I shoot in raw+. Most of the time I dont need the raw file but if there's something bright red I've got to use raw and fiddle with the luminance sliders. Usually turning down orange would help more than just red alone.

[RAART]

I have this problem on my K-3 with a particular species of red flower but not all red flowers. I wonder if the flower is reflecting light outside the visible spectrum that is messing with the sensor. Just a guess. Does not appear to be a problem with my Nikon coolpix or iPhone,

Hmmm... Right now this is a biology. I am not sure what to think about it. I shot before under similar condition red flowers and was ok but not particularly this one.

---------- Post added 06-16-15 at 02:46 PM ----------

There have been several threads that highlight other potential factors in troublesome reds that you may like to explore:

- JPEG encoding schemes and compression levels can impact red rendering, so those may be some settings to experiment with;

- the settings for noise reduction can impact red rendering. For the K-3 in particular, reduce the level of chroma noise NR, and red detail (cf the Imaging Resource test charts) suddenly comes back. LR usually sets the chroma noise NR default too high for the K-3, even for base ISO.

Using other RAW software can also sometimes have interesting impacts on red and other colours, and so experimenting with other RAW tools can be useful - Pentax Digital Camera Utility springs to mind as a good option. Every RAW processor that I have ever used seems to have a different opinion about reds.

I do have only access to Photoshop and Lightroom but it will be excellent if someone has Capture One and open the RAW file posted earlier and check for the reds.

As for the lens it was used FA100mm 3.5 in that raw file...

[wkraus]

I uploaded this file here: https://drive.google.com/open?id=0B-iswHReGS-cbnJ2U2EtdWROMFU&authuser=0

Would like to play but Google Drive won't let me download the files. I get a warning that it cannot be scanned for viruses and then if I click again I'm in an endless loop reloading the same page. Do you use Dropbox too?