Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
04-07-2012, 05:08 PM   #1
Inactive Account




Join Date: Mar 2012
Photos: Albums
Posts: 100
K-5 sensor red sensitivity?

Greetings all! I'm new to the forum, and this is my first post

I purchased a K-5 with kit lens plus the DA21 Limited in December and have been trying to learn the camera. My background is really old-school--Minolta SR T-101, Hasselblad 500C, Calumet 4x5 rail camera, etc. Although I've had digital cameras in the past, this is the first serious digital purchase for me.

Today I was doing some test shots and found that the sensor seems to be incredibly sensitive to red/orange in RAW mode. Some orange-red flowers were really blown out, despite a nominally "correct" exposure. A red gasoline can had a similar problem, although not as severe. Also, skin tones seem a bit on the pink side. Greens and grays (such as landscaping & tree bark) seem to be balanced.

So, my question is (after having searched and not found any previous threads)--is the K-5 sensor especially sensitive to reds and oranges?

04-07-2012, 06:40 PM   #2
Administrator
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 40,981
Not that I know of - it might be because of the white balance you are using, or how you're developing the raw files.

Adam
PentaxForums.com Webmaster (Site Usage Guide | Site Help | My Photography)



PentaxForums.com's high server and development costs are user-supported. You can help cover those costs by donating. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

04-07-2012, 06:52 PM   #3
Inactive Account




Join Date: Mar 2012
Photos: Albums
Posts: 100
Original Poster
Thanks for the reply, Adam--the blown out reds are in the non-developed raw (DNG) photos.

I'm using auto white balance--the green foliage around the red flowers looks fine and properly exposed. Focusing is another issue, however, and there are already plenty of threads on that topic, so I won't discuss it here.
04-07-2012, 09:19 PM   #4
Veteran Member
Anvh's Avatar

Join Date: Sep 2011
Posts: 4,616
Never had much problem with mine either.
What kind of program are you using to develop the raw and could you maybe change the colour profile?
Also what kind of screen are you looking it at, is it calibrated?

04-07-2012, 09:36 PM   #5
Pentaxian
Wheatfield's Avatar

Join Date: Apr 2008
Location: The wheatfields of Canada
Posts: 10,043
The subject of reds blooming has come up from time to time on another forum I inhabit. The concensus seems to be that it isn't a Pentax problem per se, but a photography problem ( reds were a problem with film, coincidentally). The cure, if there is one, is to watch your red histogram very carefully and expose for that histogram at the expense of the other two.
04-07-2012, 09:38 PM   #6
Site Supporter




Join Date: Oct 2009
Location: North
Photos: Gallery
Posts: 3,778
Try to use RAW and process under 'Natural' picture style.

That should tone down the reds.
04-07-2012, 10:21 PM   #7
Veteran Member
maltfalc's Avatar

Join Date: May 2010
Location: Winnipeg
Photos: Albums
Posts: 371
QuoteOriginally posted by Asha Quote
the blown out reds are in the non-developed raw (DNG) photos.
are you sure about that? if you lower brightness or exposure when you're converting your raws, do the blown reds stay blown and just get darker, or do they regain detail?
04-07-2012, 10:41 PM   #8
Ole
Administrator
Ole's Avatar

Join Date: Sep 2006
Location: Copenhagen, Denmark
Photos: Gallery | Albums
Posts: 3,783
Red and yellow easily become overexposed. I use a negative EV compensation when photographing red or yellow flowers. Apparently the light meter gets tricked by these colors. All DSLRs I have experienced share this "feature".

04-07-2012, 11:25 PM   #9
Pentaxian
JohnBee's Avatar

Join Date: Sep 2008
Location: front of computer
Posts: 4,496
QuoteOriginally posted by Asha Quote
Thanks for the reply, Adam--the blown out reds are in the non-developed raw (DNG) photos.

I'm using auto white balance--the green foliage around the red flowers looks fine and properly exposed. Focusing is another issue, however, and there are already plenty of threads on that topic, so I won't discuss it here.
I've found that MANY raw developers push the red channel to get more pop out of them. However... if you develope your image with neutral colors you'll find things to be much easier to manage.
04-07-2012, 11:37 PM   #10
Forum Member




Join Date: Apr 2010
Photos: Albums
Posts: 91
Hi, I often experience the same issue with read and magenta colors when shooting indoors but it is easily correctable. In Aperture I slightly decrease saturation and luminance of specific color. I believe there are similar tools in any RAW convertor. I'm not sure if that an Aperture (software) or K-5 (hardware) issue but since all the details are there it can be fixed.

See the attached 100% crops of image before and after correction.
Attached Images
View Picture EXIF
PENTAX K-5  Photo 
View Picture EXIF
PENTAX K-5  Photo 
04-08-2012, 12:28 AM   #11
Veteran Member
Philoslothical's Avatar

Join Date: May 2011
Posts: 1,723
I once saw an article about how various sensors handle colour, and remember that Pentax pushes reds nearly to the limit very easily. Thing is, I'll be damned if I can find the bookmark for it now. Might have been on DxOMark.

As Ole mentions above, yellows can be brutal, too. I have much more trouble with yellows, especially in warm light, than I do with reds.

The upside of this, is that if you don't blow the channel, you can get some ridiculously beautiful reds right off the camera. This is one (subjective) thing that quite a few people associate with Pentax.
04-08-2012, 07:34 AM   #12
Inactive Account




Join Date: Mar 2012
Photos: Albums
Posts: 100
Original Poster
Thanks everyone for all the replies! Did a little more research last night...turns out a silicon detector response curve pretty much peaks in the reds and into the IR. This is probably one reason the K-5 has an IR filter integrated with the sensor. There is a UV/IR Cut filter I can get for the front of my lens that levels out the red response. Right now, I only have a UV filter, so the reds are pumping through the optical system quite happily.

To answer the camera raw questions--I opened in camera raw straight from the DNG. The reds are blown without any manipulation. When I do try to manipulate (reduce exposure, saturation, etc.), I can regain some detail, but not all. In this case it is interesting artistically, but something I definitely need to control going forward.
04-08-2012, 08:13 AM   #13
Inactive Account




Join Date: Mar 2012
Photos: Albums
Posts: 100
Original Poster
QuoteOriginally posted by Wheatfield Quote
( reds were a problem with film, coincidentally)
When I shot film, I mostly did B&W, and the highest sensitivity for those films is blue to green. When I shot Ektachrome, the shift was more to blue also, but in later formulations, the E-6 films were more balanced. I occasionally shot Kodachrome which had red sensitivity, but they never became overexposed. I rarely ever shot color negative film, but I have heard there were some Fuji formulations that had punchy reds and yellows, presumably to reproduce good skin tones for portraiture. None of my experience really comes close to the behavior of the sensor with reds, LOL
04-08-2012, 09:52 AM   #14
Brooke Meyer
Guest




QuoteOriginally posted by Asha Quote
Thanks everyone for all the replies! Did a little more research last night...turns out a silicon detector response curve pretty much peaks in the reds and into the IR. This is probably one reason the K-5 has an IR filter integrated with the sensor. There is a UV/IR Cut filter I can get for the front of my lens that levels out the red response. Right now, I only have a UV filter, so the reds are pumping through the optical system quite happily.

To answer the camera raw questions--I opened in camera raw straight from the DNG. The reds are blown without any manipulation. When I do try to manipulate (reduce exposure, saturation, etc.), I can regain some detail, but not all. In this case it is interesting artistically, but something I definitely need to control going forward.
Digital sensors have a linear response, unlike film. I also shoot DNGs. I routinely reduce the Luminance & Saturation in Camera Raw for Reds and Yellows, sometimes Greens and in Theater lighting, Blue and Purple. The good news is, the detail is there, something I often emphasize by converting to B&W with Nik Silver Efex. You'll also be surprised at the effect of Orange Luminance & Saturation on Reds & Yellows.
Attached Images
View Picture EXIF
PENTAX K20D  Photo 
04-08-2012, 09:55 AM   #15
Pentaxian




Join Date: Oct 2011
Location: Savannah, GA
Posts: 4,989
QuoteOriginally posted by Asha Quote
Thanks everyone for all the replies! Did a little more research last night...turns out a silicon detector response curve pretty much peaks in the reds and into the IR. This is probably one reason the K-5 has an IR filter integrated with the sensor. There is a UV/IR Cut filter I can get for the front of my lens that levels out the red response. Right now, I only have a UV filter, so the reds are pumping through the optical system quite happily.

To answer the camera raw questions--I opened in camera raw straight from the DNG. The reds are blown without any manipulation. When I do try to manipulate (reduce exposure, saturation, etc.), I can regain some detail, but not all. In this case it is interesting artistically, but something I definitely need to control going forward.
Some monitors are set to blow out the reds. Make sure whatever screen you are looking at is calibrated.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
camera, dslr, k-5, k-5 ii, k-5 iis, k-5 sensor, k5, pentax k-5, sensor
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Autofocus sensor sensitivity starbase218 Pentax DSLR Discussion 3 12-24-2011 05:02 AM
expanded sensitivity ? mrfatpooh Pentax K-r 13 07-03-2011 07:52 AM
Expanded Sensitivity rvannatta Pentax K-5 10 05-19-2011 02:27 AM
Why would you want Expanded Sensitivity off? Javaslinger Pentax K-5 8 01-19-2011 09:16 AM
Infra Red Sensor on K10D for Remote channeler Pentax DSLR Discussion 18 04-08-2008 07:06 AM



All times are GMT -7. The time now is 07:28 PM. | See also: NikonForums.com, part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top