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Old Mar 18, 2007, 2:25 PM   #21
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So based on these tests I think maybe the SR just doesn't work well with this Sigma lens? Do any of you think it would do any good to send the Sigma in and have it adjusted? Or is this about what I should expect?

If this is what I should expect what two lenses would you suggest I replace the Sigma with to cover the same area but get quality like that from the 18-55 or better? Without breaking the bank?

Thanks,

Robert
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Old Mar 18, 2007, 2:29 PM   #22
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How is the Pentax 50-200? Since I have the 18-55, this should fill out the zoom range. I know it won't match the 300mm end of the Sigma and I don't care, I want better image quality and better SR support?

Anyone with samples from this lens (full size, no editing)?

Robert
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Old Mar 18, 2007, 3:37 PM   #23
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The only thing to help you with lens choice is what I discovered with a rather cheap but new Voigtlaender 28-210 zoom and a Pentax-FA 28-105/4-5.6 I got on ebay (a 7 years old lens).

The sharpness and detail is MUCH better from the Pentax, I use it now as a walkaround lens and am much happier with my results.

Really - for your sharpness problems, go out on a bright day and try for some everyday shots in a garden, of sculptures, buildings and stuff. Be sure to use different settings, including higher ISO up to 800 and f-stops, just get a feeling for how the camera "sees" things.

It really takes time to adjust to that different DOF - I still struggle on that too. You can't delete 2+ years digicam use so easy from memory... it's just DIFFERENT photography.

Good luck - as for a tele zoom, most people here say good things about the Pentax 80-320 and the Sigma/Tamron 70-300 Macro lenses. I'll look for a good price on one of these too - that should almost complete my current lens needs.

Good luck and happy snapping with your k10d!

Th.
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Old Mar 18, 2007, 10:20 PM   #24
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I have the DA 50-200 lens - it's quite sharp, though mine is a bit softer at 200 than at 100. It's afairly inexpensive, workmanlike lens and I use it all the time. If you want to see some examples, and how they compare to the kit lens, take a look at this thread about focal lengths. The pictures aren't the greatest, they've all had a bit of USM applied (as I recall, I usually add some to just about anything I shoot, especially if I resize it downwards), but no extensive pp - I didn't spend a lot of time on them: http://www.stevesforums.com/forums/v...mp;forum_id=94. They were processed with PhotoLab and PS6 because my computer was still in the shop and I was using my hubby's slow, old, limited computer.

Just my opinion, but I don't feel a need for a lens between 200 and 300, so having the kit lens, the DA 50-200 along with the A*300 is perfect for me. The quality of the A*300 is outstanding, the DA 50-200 is light enough to work well for a walk-around for me andpicture quality ispretty good,and I have the kit lens for wide angle stuff (not my usual thing, though I sure regretted not having it with me on Friday whenI had the opportunity to wander around a not-yet-completed fascinating building, but that's another story). Others like their DA 50-200 lenses more than I do (some really love them), and I plan on replacing mine with one of the new DA* lenses coming out (maybe two - I'm still thinking about the 60-250 due out in Dec.).
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Old Mar 18, 2007, 10:32 PM   #25
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Robert Barnett wrote:
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So based on these tests I think maybe the SR just doesn't work well with this Sigma lens?
NO!!! The 70-300mm and the 28-70mm are FINE lenses for their minor cost, and do work well in BOTH focus/IQ and SR.

Just the 28-300mm is just a big compromise in both cost and construction.

I'm sure SIGMA would likely tell you nothing wrong with it... it just is what it is....

A signifficantly compromied system for the convenience of not taking atvantage of what a SLR is about.... changeabe lenses for changing situations.... they are NOT about never taking a lens off....

Might as well just stick with a high end P&S for that.


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Old Mar 18, 2007, 10:38 PM   #26
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I went out and shot some shots with my manual f2 50mm (have the auto focus one on order and should be here on Monday). I have no doubt now that the camera is fine. I think I am going to pick up one of the 50-200 and once I have it I am going to contact Sigma and have them take a look at my 28-300.

I don't know why, but it doesn't seem that SR works well with this lens. Plain and simple. No issues with any other lens I have. Just the 28-300. So I am starting to think that there is something wrong with it.

When I was doing my research before buying the lens I heard a lot of things about Sigma quality control and that it is very hit and miss. If you luck out and get a good copy they are good, if not you need to send it in. So that is what I am going to look at. Once it comes back I will decided them if I want to keep it our not.

I chose the 28-300 because I wanted to match the zoom range my FZ30 had. However, now I just want good sharp detailed images if that means less zoom so be it.

Robert
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Old Mar 18, 2007, 11:35 PM   #27
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Well I never used the 28-300m on a SR camera but had enough problems as is on my old Canon Rebel.

It could very well be for the reasons suggested earlir in the thread that would have no apparant effect on a non SR camera.

>>"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."<<

Again a lot of optical/construction compromises to get that WIDe plus semi super tele all in one lens... on most standard cameras would not be an issue... but is to a SR, needing that accurate FL info for the SR to do its correction properly.
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Old Mar 19, 2007, 1:28 PM   #28
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I am not sure I follow on this. I set the lens to 150mm to focus on my test chart. I have auto focus on. What is the problem? Also I thought the:
Sigma Zoom Wide Angle-Telephoto 28-300mm f/3.5-6.3 DG Macro Autofocus Lens for Pentax AF SLRWhile not digital only was designed to function correctly on a digital SLR as well as a film SLR? Just asking I don't know.

My 50mm f1.4 arrived and the images are incredible. So once again I think it is the 28-300 which I was shooting with the most.

Robert

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Old Mar 19, 2007, 5:20 PM   #29
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Robert

You will always find prime lenses sharper than zooms, simply because the glass is set to be as perfect as can be achieved at one focal length.

Something like your 28-300mm Zoom is a very long range that the lensis expected to focus perfectly. There is a compromise, and that is usually softer focus.

If they could manufacturea lens that was tack sharp from 10mm to 400mm you would put all other lenses out of the market, but that cannot be achieved, well at least not yet. :blah:

I am glad you had tried a prime lens on your camera and can see the camera is CAPABLE of producing good sharp images and any loss of image quality is more to do with the lens selection. I suppose thats why everyone craves Pentax Limited lenses.

I use Sigma lenses and am quite happy with them, even though my 25yr old Pentax SMC-A 50mm f/1.7 has more contrast and sharper resolved images than my 12month old 28-70 f/2.6 EX Sigma lens. One cost me $500 and one cost $30 second hand, but I like the ability of the zooming and constant f/2.8 and am willing to trade off a little image sharpness for that.

I am not saying that my Sigma lens is soft by any means, but there is sharp and then there is SHARP. It is unfair to compare image sharpeness between a zoom and a prime specially when the zoom range is very long.

Enjoy your K10D and enjoy your new found budding LBA, because now you have seen the difference between lenses, you will start looking for lenses. Some of my sharpest lenses around are the older ones (Pentax, Takumar, Tokina) which I fond on eBay and second hand shops.

Crash
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Old Mar 19, 2007, 10:29 PM   #30
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Robert Barnett wrote:
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Ok, this sample has the 18-55 image on the bottom and the 28-300 on the top. Again look at the detail and sharpness. Again the in camera settings are Saturation and contrast at factory defaults with sharpness at max.

Robert
Wel that is pretty severe (awful) might actually be something physically wrong with your 28-300mm beyond the far from perfecton the optical compromise it is.... never great especially at the far end.

But I would always expect the 18-55m for its range to be much sharper.
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