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05-24-2010, 12:24 PM   #16
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QuoteOriginally posted by Class A Quote
I find this hard to believe. Even if a sensor already out resolves a lens, making it resolve more, will still improve the image quality (because MTF curves are multiplied in an optical chain). Something else must be going on, if you really observe a degradation when going to a better resolving sensor.
I think, I am not alone with these observations. I rarely used the 25-135 to begin with, but bought it initially as a walk-around lens for my istDS, when I would not be able to carry my usual gear with me on hikes. The lens performed quite well for such a zoom. Later I used it with a K10 during a family wedding, were I luckily wasn't the official photg, but made some snaps. The lens failed miserably, with extremely low contrast, though the images were sharp. Even at f/8 I found the results unuseable.

I have since read quite a few reports on very similar experiences. I do not have a real explanation myself, because downsampling the higher res image to a lower pixel count should yield results very much like that of the lower res cameera - but in a few cases it doesn't.

Ben

05-24-2010, 12:32 PM   #17
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No pics? It didn't happen. Unless there is something wrong with AF, even with the kit lens you should be getting images that are plenty sharp. Maybe it has to do with the way you are post processing? Impossible to tell unless you post a picture.

Below is a short article that I think all DSLR owners should read. Particularly those who have high-resolution cameras like the k-7. Get over the fact that it says Canon on it. It applies to sharpness of all DSLR's, and might answer some of the multitude of questions about "why isn't my **insert camera brand** sharp?"

Pixels and Image Size link

The last 3 paragraphs in particular, discuss the issues involved in sharpness of cameras with high-resolution sensors. Just substitute "k-7" for the camera they are talking about. It is directly applicable to you since you are moving from a lower resolution camera (k100d with 6MP) to a much higher one (k-7 with 15MP).

I doubt the issue you are having has anything to do with a "camera outresolving a lens." Some of the sharpest pictures I ever took with the k-7 were with the 18-250.

Last edited by PentaxPoke; 05-24-2010 at 12:44 PM.
05-24-2010, 01:39 PM   #18
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Another forum member I recall had a similar issue. He ended up sending it in for warranty repair and they replaced the SR assembly thingy something and it fixed the problem.
05-24-2010, 01:56 PM   #19
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Mel might be referring to my experience. Last September I took the K7 and my DA40 and DA18-250 to Italy for 3 weeks. 3000+ images later I determined I had either succumbed to Parkinson's or something was wrong with the K7. Both lenses produced the same results, unsharp at any F stop/ISO (tripod or not). Interestingly however, any images I shot of ceilings or manhole covers seemed tack sharp. Interesting I thought, SR probably didn't come into play. I sent it into C.R.I.S. with examples and they in turn replaced the entire sensor assembly. Well, either my Parkinson's has miraculously been cured or CRIS did the trick, because I'm 100% happy with the camera now.

If you bought it new, and the results from the tests mentioned above are either inconclusive or repeat your concerns, you might need to send it in. I'm most happy I took the chance..

05-24-2010, 04:55 PM   #20
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QuoteOriginally posted by Ben_Edict Quote
The lens performed quite well for such a zoom. Later I used it with a K10 during a family wedding, were I luckily wasn't the official photg, but made some snaps. The lens failed miserably, with extremely low contrast, though the images were sharp.
I see a possibility that the differences could be due to different lighting situation, e.g., side/back light that was present at the wedding. Or the lens condition has somehow deteriorated over time. I'm sure you are aware of these and other potential factors and I don't take your conjecture lightly as I know you are knowledgeable and a logical thinker. Still, I'd be wary to purport a hypothesis which seems to be based on shaky ground.
05-25-2010, 04:38 AM   #21
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Just wanted to post a couple of photos to show what the K7 is capable of. Second one is a crop of the first -- taken with the (somewhat lowly) DA 55-300. Definitely quite sharp.





These were taken in RAW, converted in ACR. I use the clarity slider in ACR, but don't usually sharpen otherwise.
05-25-2010, 05:17 AM   #22
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QuoteOriginally posted by ntlegg Quote
Compared with my K100D photos, the K-7 images generally just seem less sharp. For reference, I am using the same kit lens as I used with the K100D (saving up for an upgrade).
Nick,

as questions like your's may yield no useful answer, I kindly require you to do the following:

1. Set your kit version I lens to 35mm f/8
2. Put your camera on a tripod and use something like 1/15s
3. Print a black square and fix it to a wall, 5 tilted (the print, not the wall )
4. Use contrast AF to focus, take a shot (camera at default JPG settings, 2s self timer)
5. Crop to the printed square and attach the crop here, without changing the size of the cropped image!
E.g., if your original is like 4500x3000 and you crop to a 10% 450x300px center region, the attached image must be 450px wide.

Once you've done that, I will probably be able to tell you what your problem is.
05-25-2010, 10:50 AM   #23
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QuoteOriginally posted by Ben_Edict Quote
I think, I am not alone with these observations. I rarely used the 25-135 to begin with, but bought it initially as a walk-around lens for my istDS, when I would not be able to carry my usual gear with me on hikes. The lens performed quite well for such a zoom. Later I used it with a K10 during a family wedding, were I luckily wasn't the official photg, but made some snaps. The lens failed miserably, with extremely low contrast, though the images were sharp. Even at f/8 I found the results unuseable.

I have since read quite a few reports on very similar experiences. I do not have a real explanation myself, because downsampling the higher res image to a lower pixel count should yield results very much like that of the lower res cameera - but in a few cases it doesn't.

Ben
There's a possibility it's not specific to the higher res sensor, just a DIFFERENT sensor. As I understand it, digital sensors tend to be a lot more reflective than film, and also behave differently when given non-perpendicular illumination. This is why you now see "digital optimized" full frame lenses - the main difference is improved antireflection coatings. Good lenses from the film days (like Pentax SMC lenses) had sufficient AR coatings to begin with, but cheaper lenses sometimes weren't sufficient - the digital era has increased the "minimum bar" for lens antireflection coatings.

So the K10D's sensor may have been more reflective than the *ists, or behaved differently to non-perpendicular light.

05-25-2010, 11:04 AM   #24
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There is no reason to continue in this thread until the OP provided the info requested.
05-25-2010, 11:24 AM   #25
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QuoteOriginally posted by falconeye Quote
There is no reason to continue in this thread until the OP provided the info requested.
Two days later and his original post is still the only one he has made on the entire forum. Drive-by posting, maybe?

Last edited by Parallax; 05-25-2010 at 11:32 AM.
05-25-2010, 12:28 PM   #26
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Well, i have put three versions of one picture on line to compare: One RAW (PEF), One developped with Adobe Raw ( default settings) and one developped with DxO (default settings) I'm not really enthousiastic with the default outcome without correcting, what do you think of the default JPG and Camera RAW is this the expected Pentax sharpness?? Or does the camera needs some tweeking. Finally the result from DxO is in my opinion a big improvement. You can find the pictures over here to look at or download for further investigation look here for K7 samples
05-25-2010, 04:19 PM   #27
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I assume you're judgng by looking at the faces of the children, which are indeed softer than one might hope for. But that's to be expected, since the shutter speed wasn't fast enough to completely stop their motion, and also, the faces don't seem to be where the camera chose to focus. Instead, check out the posts in front of the children - see especially the area around their feet. I don't think there is anything to complain about sharpness-wise there, considering you're using a "superzoom". The ACR version does indeed seem softer than the DxO version, indicating that if you use ACR, you'll probably want to turn sharpening up from the default. But none of this really has anything to do with any limitations or issues with the camera.
05-25-2010, 04:43 PM   #28
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G'Day All,

I (rather sheepishly) have to admit a similar dissatisfaction with the images from my K7.

I bought the K7 as 'body only' and a couple of secondhand lenses.

From new nearly all my shots have been in the 'not worth keeping' category, soft/blurred. Some clearly my fault but most just wrong.

Images on this site taken by others with the same equipment in similar conditions were much sharper than anything I could produce.

So, what was the issue, Me the K7 or the lenses?

I purchased a number of other secondhand lenses and got similar results.

I used a tripod with 2 sec. delay and got similar results.

I checked for front/back focus, not an issue.

I finally got so frustrated I bought a Kx body and at last got the quality of images I expected from the K7 (using the same lenses).

I have posted some images on filckr but the photos from the K7 are some of my best (image quality) as I have deleted most and had trouble uplaoding to flickr this morning. I will add some more typical shots later.

I have not yet done a side by side comparison of the K7 and Kx but will do so when I get a chance.
05-25-2010, 05:01 PM   #29
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QuoteOriginally posted by alfa75ts Quote
G'Day All,

I (rather sheepishly) have to admit a similar dissatisfaction with the images from my K7.

I bought the K7 as 'body only' and a couple of secondhand lenses.

From new nearly all my shots have been in the 'not worth keeping' category, soft/blurred. Some clearly my fault but most just wrong.

Images on this site taken by others with the same equipment in similar conditions were much sharper than anything I could produce.

So, what was the issue, Me the K7 or the lenses?

I purchased a number of other secondhand lenses and got similar results.

I used a tripod with 2 sec. delay and got similar results.

I checked for front/back focus, not an issue.

I finally got so frustrated I bought a Kx body and at last got the quality of images I expected from the K7 (using the same lenses).

I have posted some images on filckr but the photos from the K7 are some of my best (image quality) as I have deleted most and had trouble uplaoding to flickr this morning. I will add some more typical shots later.

I have not yet done a side by side comparison of the K7 and Kx but will do so when I get a chance.
Seriously. Read Rormeister's post. He had a sharpness issue and there was actually something wrong with his camera. And from what I understand, there has been more than one camera that had this issue.
05-25-2010, 05:13 PM   #30
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I did when he first posted it and until this thread opened it was the only report of similar issues I had seen.

I know it's a fault of mine but I like to know beyond doubt that something is faulty before getting it fixed.
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