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Old Mar 17, 2007, 1:54 AM   #1
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Ok, I don't want to start and flame wars. My aspestous underware is at the cleaners. However, having taken well over 3000 shots with my K10D I am beginning to wonder about focus issues and I am concerned about how well the shake reduction works. As in it doesn't seem to be very good, not even as good as the SR ok the K100. It doesn't seem to come close to the Panasonic FZ30 either.

I chose the K10D because I have a nerve problem and I shake pretty good so SR was a very important feature for me and I just don't think it works well on the K10D. But, right now I want to deal with focus issues and see if I can't rule that out as the reason for soft almost blurred images. I will deal with the SR later.

I downloaded a focus test chart and took four pictures. Two in DNG processed with ACR 4, both with my Sigma 28-300 at 300mm. One has shake reduction on and one has it off. Both were shot on a tripod (I don't usually use a tripod).

The second two are basically the same as the first two except shot in JPG mode in the cameras bright mode with sharpening set to max. Again one with SR on and one with SR off. Both on a tripod.

To me they look fine and I do see a bit of difference between the images with SR on and Off, SR seems to be better. Can you all take a look and let me know what you think?

http://robertbarnettphotography.smug...0682#136535164

NOTE: See the captions under the images for details on which image is which. To see the original images move your mouse over the larger image on screen and then choose the size you want. These four images are 18MB total.

Thanks,

Robert
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Old Mar 17, 2007, 3:08 AM   #2
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Well one thing I can say if its anything like the Canon version the Sigma 28-300mm is significantly soft at 300mm especially wide open. Contrast left something to be desired at that end too in less than bright daylight.

Focus matters are usually more the lens not the camera.

This was my main reason for dumping the 28-300mm on my old Rebel and switching to the Sigma 70-300mm, (as well as a 28-70mm) and purchased it again for my K10D. Much better lens and results... and as you have probably noticed quite popular here. (Along with the nearly same Tamron 70-300mm)

Personally I find the SR quite nice... no SR is a cure all though.... the steadier you are the more extreme the results you can get, in shutter slowness... I have found almost always 2 stops and at wider FL's or being able to brace on a rail or something often 3.

In his just released review of the K10D, actully Steve felt it improved over the K100D.
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Old Mar 17, 2007, 3:43 AM   #3
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its the extreme zoom lens, having 28mm all the way to 300mm make lens design complex and you will have a compromise at one end with sharpness

- my sigma 100-300 f/4 EX is tack sharp wide open at f4 at all focal lengths

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Old Mar 17, 2007, 12:18 PM   #4
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I am aware of the difficulties with the 28-300. However, I don't like changing lenses. Too much trouble and that is not why I bought a dSLR. If I could have gotten the sensor size of a dSLR in a super-zoom advanced point and shoot like the Panasonic FZ30 (I could careless about the size) I would have done that. To me the changing of lenses it a strike against dSLR's. I also know I am in the minority in this and that is fine.

The problem with the softness is that I don't find any of my lenses to be that sharp and I have an older manual 50mm f2, a Pentax 10-17 fisheye and the kit 18-55. None of them seem to be anywhere near as close to what I get with the Panasonic, noise and things like that aside.

As for the SR, having used the Panasonic for near 20,000 photos and having used a friends K100 Pentax for 2 months I can't say that the SR in the K10D works all that great.

So what I am trying to do is figure out if I have a faulty lens that needs to be sent in, a faulty camera (be it a focus issue or something wrong with the SR) or if everything is working fine and I am just plain disappointed in the final quality of the whole thing. I need to figure out which it is before warranties are gone.

Robert
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Old Mar 17, 2007, 1:09 PM   #5
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One possible reason is the Sigma lens. Many of the "megazooms" Sigma lens does NOT have constant focal length throughout its focusing range.

So when you set your zoom at 300mm, and focus at infinity, the focal length should be as specifed: 300mm.

But as you focus closer and closer (e.g. your test chart), even though the zoom is still set at 300mm mark, you will find that the actual focal length could be much less than 300mm (very apparent if you compare the Field of View with a real 300mm lens).

This would create problem for the SR system, which receives info from the lens that it is set at 300mm, while in actual fact, it may be over-compensating, as the real life focal length is less than 300mm.

That's why when I see people reporting SR not working well, I would first ask or check which lens was being used. 9 out of 10 times, it was a Sigma "Megazoom"; the other frequently mentioned lens was the 18-200mm.

Most Pentax lenses are not affected by this problem. For example, the DA 50-200mm lens has constant focal length throughout its entire focusing range. It is 200mm at infinity, and it is 200m which focusing close. And this works well with the SR.






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Old Mar 17, 2007, 2:29 PM   #6
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Well, I will check this out with the two Pentax lenses I have, the 18-55 kit and the 10-17. I will report back shortly.

Robert
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Old Mar 17, 2007, 2:51 PM   #7
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Robert,

I too came from a Panny FZ30 and had pretty much the same problems. I was hit and miss getting tack sharp images. Are you familiar with the debug mode in the K10D? Thia has been a MAJOR revelation to me! I own 6 lenses for my K10 and every one uses a different AF setting. Mine go from -70 (Pentax DA 50-222) to +20 (Pentax 50mm f1.7). But once properly set, each lens is spot on! Do a search on dpreview's Pentax SLR Talk Forum for "debug mode" and you'll find all the answers you have there. Unfortunately, if you've updated to the latest firmware it's too late.

cheers, Wayne
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Old Mar 17, 2007, 3:09 PM   #8
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Its too late. Already updated. I wouldn't have used it anyways. If Pentax wanted non-techncians to use it they would have made it public. I am also a firm believer that a product should work as shipped and that if you have to jump through hopes to get proper functioning then there is something wrong.

Robert
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Old Mar 17, 2007, 3:20 PM   #9
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The other as pect of the 28-300mm is that it is an "economy" lens so limited optical "expensive" construction involed.... for instance another 10x is the 50-500mm BIGMA, but there are reasons it costs $1000, besides the added glass size.

Also it starts from a "normal" FL.... that is another compromise in the 28-300mm it trying to be both a wide lens and long tele in the same lens construction, necessitating some compromises, that unfortunately makes its long end suffer in image quality.

Swapping lenses can be a pain but my Sigma 28-70mm and the 70-300mm together were about the same cost, actually a bit cheaper than the 28-300mm. Also several stops faster in the wide to normal range as the 28-70mm is a f/2.8-4 lens.


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Old Mar 17, 2007, 3:55 PM   #10
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@Robert

The pictures look fine to me, I picked the "SR off"/"RAW" picture and post-processed a small area:



If you look for sharpness and strong contrasts - can crank up the in-camera sharpness and contrast to +2 and you will get something like this right out of the camera. From RAW you only have the chance to post-process.

There are other issues you should look after:

- DOF: it's different for 35mm, dSLR, digicam
- lenses and it's character: watch for reviews on your lens - no lens is "perfect": do different tests with different f-stops and zoom factor.

If you got specific questions - just ask. I am in the same boat as you are - coming from a Oly C770 UZ and using a Pentax *ist DL2 now I know what it feels like

Yours,
Th.
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