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04-23-2012, 04:54 AM   #1
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Macro - Zeiss 25/f2.8 ZK - overdriving color question

Morning, Well I usually shoot landscapes, citylights and the like. However, I acquired a new Zeiss 25mm f2.8 ZK. Just saying that the lens is nice is an understatement. I really want to use it for 'scapes, but the lens has this extra additional capability. The focus throw adjustment takes 355 degrees of the 360, and close focus is at 6 inches. 180 degrees or half of the focus adjustment throw is from 6 inches to 12 inches. This coupled with the f2.8 aperture makes this (for me) a real macro lens. So, I have been playing around with it quite a lot.

In my playing, I have come across a number of things. Its spring here in the desert, well at least the previous weekend anyway - its now 100+ degrees, but the flowers were out and I went out and shot a few. What I found was that the yellow ones, especially during the day, really over drive and over saturate the metering on my K5 (center averaging). It took a while, but I am wondering if just center spot would provide better metering, so that I would not be over saturating the color, which I am finding just blows out the fine detail. This did not dawn on me until the second or third round, trying different things back on the computer post processing the images. The yellows just blow the detail out of the water. At first I though I was just out of focus, but even hand holding which is difficult, I am pretty sure that I was careful and got it, and even opened up the aperture to get a better depth of field, and the color just overwhelmed everything.

I never had a lens with this capability and its a nice weapon to have in the bag (its HEAVY, but really nice!).

Anyway - here are a few shots - with the last one showing the overblown highlights....

edit - by the way the last image was 1/2000 sec at f4 with an ISO of 400 and I was no farther than about 7 inches from the cactus needles. I kept getting the buds perfectly, but the flower details are just mush (however in the viewfinder, they appear perfectly focused with great detail).



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Last edited by interested_observer; 04-23-2012 at 05:12 AM.
04-23-2012, 05:03 AM   #2
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Turn on your highlight blinkies and you will know immediately that the camera is overexposing. Then just dial the exposure down a bit to your liking. Hope this helps,
04-23-2012, 05:09 AM   #3
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Thanks!!! I would have never thought of that.

04-23-2012, 06:13 AM   #4
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Some of the reviews of ZK lenses on this forum have suggested that they underexpose.
That has not been my experience with them on the K-x.
With that camera, I normally compensate to have 2/3 EV underexposure,
and that setting works as well for me with the ZKs
as it does with DA Limiteds, a Tamron A16P, and legacy lenses.

04-23-2012, 10:06 AM   #5
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Ask Zeiss?

Have you contacted Zeiss.de in Germany by e-mail? They are very good in answering technical questions, although their terminology is little bit different and knowledge on Pentax dSLR is also limited. You can send them sample photos and ask what they think.

I have 3 ZKs that always underexposure ~ half stop and 1 always accurate. When I set in 1 of the underexposed lens to check for an unrelated issue, they replaced it and the exposure is bang on now.

PS: Your first & third photo are overexposed ~ a third to half stop to my eyes.

Last edited by MJL; 04-23-2012 at 10:14 AM.
04-23-2012, 11:17 AM   #6
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It's the way flowers reflect certain light rays to attract insects ( they don't see colors as we do )
Some lenses due to the coatings accentuate some colors, Pentax usually over exaggerate Reds. Use -EV to change exposure
but a Polarizer works best.
Another way is knowing that the lens blowsout yellows, setup a custom white balance to compensate for it.
The only lens I have that is color neutral on all flowers is an Adaptall 38-100, it has a browish gold tint unlike any other that I own.
04-23-2012, 07:55 PM   #7
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It's always a good idea to underexpose 1/3 - 1/2 anyway since your RAW file will keep the data. You can always bump the shadows up a bit. On the other hand, if your highlights get clipped, there's no detail to recover anymore.

I don't know if it's the sensor or the way manufacturers tune cameras, but digital cameras tend to blow quite a lot on reds, yellows and purples. It's more visible on some lenses, but it's always there to some extent.
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