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07-24-2013, 07:30 PM   #1
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Pentax SMC M 50mm on K-30: Blue Tint

Today I mounted a manual foucus 50mm f2 on my new K-30 body. I enthusiastically took a few photos (mostly wide-open, in case that's relevant) and noticed they had a distinct blue tint to them. I quickly swapped my lens to the 18-55mm (with hood on) and snapped a few again: Same subject matter, same place, all a few minutes apart. But the 18-55 produced images with a colour balance that I would call excellent. Why the diff??

Oh yeah, I can't post any examples since I won't be near my PC until next week. But anyone whose seen this will know exactly what I mean.

Interestingly the tint can be elimiated by applying the Color effects filter in-camera. I am more perplexed (and curious) than ever.

07-24-2013, 07:41 PM   #2
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What white balance setting are you using? Also, the coatings of some lenses, especially older ones, can leave a color cast. This can change based on the ambient light. The coatings on modern lenses are pretty much better.

Many of us use some kind of imaging editing software (I use Lightroom), and shoot in RAW, and fix these things after the fact. You can also use the custom white balance setting along with a known white (or neutral grey) to get it right the first time.

Look here: k-7-how-do-white-balance-question


Last edited by Kozlok; 07-24-2013 at 07:51 PM.
07-24-2013, 07:42 PM   #3
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I find my M glass has a bluish tinge to the CA - M85/2 is known for it.

besides cropping, this is SOOC.... M85/2 at f2.8 or f2.0 (cant remember)
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Last edited by mattt; 07-24-2013 at 07:46 PM. Reason: added photo
07-24-2013, 07:56 PM   #4
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Kozlok, I use AWB. That didn't seem to make a difference when using the 18-55mm where everything just turned out. Before I do any post-processing I'd really like to know what the cause is. I've seen some similar complaints going back a few years, but no one posted an answer.

mattt, this definitely isn't CA, it's a consistent colour across the entire photo. The entire pic is evenly tinted. Again, I apologize for not being able to post samples right now.

07-24-2013, 08:48 PM   #5
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I use K and M lenses on my K5 quite frequently and haven't noticed this vs my DA lenses as a pattern, but I rarely use AWB. AWB isn't neutral, it sets it to something based on what it thinks it sees. It could be setting the WB differently with each lens.

Try setting the WB to something, like cloudy or shady and do the same test. That would tell you if the camera was forcing that tint or if it is coming from the glass.
07-24-2013, 08:54 PM   #6
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QuoteOriginally posted by troika Quote
I use K and M lenses on my K5 quite frequently and haven't noticed this vs my DA lenses as a pattern, but I rarely use AWB. AWB isn't neutral, it sets it to something based on what it thinks it sees. It could be setting the WB differently with each lens.

Try setting the WB to something, like cloudy or shady and do the same test. That would tell you if the camera was forcing that tint or if it is coming from the glass.
Just curious, do manual lenses affect the camera's WB setting?
07-24-2013, 09:09 PM   #7
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Seen this as well on a M50/1.7. In their day, they typically had a skylight filter on the front to warm the images a touch. But I also found on digital that 30 year old skylights filters added odd tints, maybe the dyes in the filters deteriorating?

And yes, the M85/2 can go a little crazy with blue CA at F2-2.8 but it seems very neutral with colours overall which I imagine was a good trait for a portrait lens.

I switched to Raw to resolve M lens wb issues. The white balance is then just a parameter stored in the file and not baked into the image like jpeg. I found that when correcting wb, the tint often also needs a little tickle. End results can be good and worth the extra step.





M50/1.7 from Single in March 2013.
07-24-2013, 09:17 PM   #8
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I don't know. I've never tested it. The thing with AWB is that you (I) don't know what they do or how they do it. Someone knows, presumably. There's a program and it measures something and makes a decision about where it thinks the WB should be set. I'll test with a few of my lenses later and see what happens, I'm curious, but it would be really interesting on the OPs K30 and with his lenses, since he's noticed it happening.

From my limited experience, I'm not sure I agree that modern coatings are intrinsically better. I love old glass and I feel like I get consistent and predictable results with them. With the DA lenses I've had or used, I've gotten some good results, but not necessarily better and not necessarily more consistent. Then again when I am using a DA lens, I'm almost always letting the camera make more decisions for me (AF).

WIth out a doubt, Pentax DSLRs do or should be all rights, understand a DA lens much more clearly than anything else you mount on it. The camera recognizes it as soon as it's mounted and it does things like tune the shake reduction appropriately for the focal length (I just learned). That coating was designed for that sensor and the programing in the camera's software. Call it an educated guess that it may also think "Oh, a DA 18-55 lens with blah blah coating set at this apreture and the user wants me to pick a WB setting. Cool, no problem".

With an M lens, it says "K or M Lens" and asks you for the focal length and that's it, except for stop down metering. I don't actually know how the AWB algorithm works, but it's a good theory that it might not understand in the same way through an M lens what it does through a DA lens and maybe in the OPs circumstances, it guessed "Tungsten" incorrectly. Easy to test. Set the WB to Sunny or Shady or Cloudy and shoot something with one lens, swap it for the other and shoot again in the same light.

If the M lens still has a consistent blue tint comparatively, then it's something about the lens. If not, it was the camera making a different choice for you based on the lens you had mounted. I'm curious now too.

You might also shoot the M lens with AWB and then the DA lens set to Tungsten and see if the results are closer. That would suggest that the camera was setting itself that way with the M lens.

07-24-2013, 09:35 PM   #9
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Thanks all for taking the time to reply. Although my M50 came with some sort of filter, it was not on when I first noticed the tint. Since I was kinda testing the lens I made sure it was off. In fact, I did another test after putting the filter back on, and I didn't notice any difference.
Kozlok's theory regarding different coatings on the older lenses brings up some interesting questions. Hopefully I'll have time to try some more tests tomorrow.
07-24-2013, 09:52 PM   #10
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I did a quick test. Different lenses, different camera, different lighting, but I was curious and am procrastinating some work.

I shot my piano keyboard with a DA 40 ltd and then with an SMC 55 with the camera set to AWB. Then I did the same with the WB set to Tungsten. I've had the 40 for less than a week, by the way, so I'm just getting to know it.

Essentially, the 40 in both settings looked great, I'm really impressed with this lens early on (but I digress). The white keys in both DA40 photos were pretty white, just like what you would expect in a keyboard photo. The difference in white between the K lens with the camera set on AWB and with it set on Tungsten was pretty noticeable. That sort of supports my theory that my camera is better at making a AWB choice for me with a DA lens than it is with legacy glass. (I think Tungsten is the right setting the room I'm in).

The thing is, though that I don't think my keys are that white. It's an old, well played piano and they're kind of yellow. I don't think the SMC 55 replicated the off-white perfectly in either setting, but I think in the both settings the DA made it whiter than it actually is. I don't know...my theory is unraveling. It's interesting, I'm not sure what it means.
07-25-2013, 07:36 AM   #11
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I just took the M50 out for a quick spin this morning. The skies shifted between sunny and cloudy, so I made sure to sample both conditions. All I can say is: The colour reproduction was absolutely perfect. So now I'll wait for evening in the shade (as yesterday) and see if the blue tinit comes back.
07-26-2013, 02:25 AM   #12
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My experience of Pentax M-era lenses is that they have a colour response which is a bit subdued at the red end. If there's not much red in the image, you won't notice anything, but if there is, the net result is an image which appears to have a blue cast (and somewhat low contrast).

This is in comparison with most other lenses, whether of that era or modern Pentax lenses (which have a particularly good colour response).
07-26-2013, 08:45 AM   #13
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I've found I can remove the blue cast in my pictures by setting white balance to shade mode. I've tried to duplicate the results but I've had commitments in the evening and the weather conditions here haven't been quite right, either. More testing on the way...
What I did notice was the pictures most heavily affected were taken with the aperature set at f2 and f2.8. Those taken with the 18-55mm lens were not affected at all at any setting.
I'll post a few sometime next week to give a clear comparison between my two lenses.
07-27-2013, 10:20 AM   #14
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QuoteOriginally posted by m42man Quote
My experience of Pentax M-era lenses is that they have a colour response which is a bit subdued at the red end.
I can't respond to the OP's issue since I don't have a K-30, but I know that there is no particular color cast or shift with my M-series glass on the K10D. In fact, the only lens on my shelf that has a particular cast to it is my Sigma 50mm macro. That lens has a definitive "warm" cast.


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07-28-2013, 06:59 AM   #15
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Please remember that when your subject is in the shade on a sunny day it is being illuminated by the blue sky only. I would expect a slight blue tint on subjects in the shade.
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