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08-27-2017, 09:57 PM   #61
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QuoteOriginally posted by stevebrot Quote
My question as well. While just about any focal length has been used for landscape work with the 24x36mm format, greater utility tends to be had at 35mm and shorter. That being said, many of us learned and shot for years with a 50mm "normal" lens attached to the front of our camera and for most of us, landscapes were part of the mix.

What is the "best" lens for landscape? The only criteria are reasonably sharpness across the field with good contrast. The choices run into the hundreds, but these I can recommend...
  • Super/S-M-C/SMC Takumar 55/1.8
  • Pentax-K 55/1.8
  • Pentax-M/A/F/FA 50/1.7 (with possible exception of the "A" 50/1.7 due to pervasive aperture ring problems)
  • XR Rikenon 50/2 (PF Reviews...note that reviews complaining of plastic build are not this lens. I need to update the example links on my review )
  • Carl Zeiss Jena 50/2.8 Tessar (M42 with long product run...PF Reviews)


Steve
What Steve said about the XR Rikenon is right there. I got one for under 15.00 and it is better than my skills at using it. Very nice images and the mount is metal, and as stated earlier, no contacts for A use. Green button metering, so fully manual.
I actually prefer the images from it over my M 50 1.7, which I may list in the sale forums in the near future.


Last edited by SSGGeezer; 08-27-2017 at 10:08 PM.
08-28-2017, 12:52 PM   #62
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dfa 28-105

QuoteOriginally posted by awscreo Quote
Might want to test the lens for decentering. I believe my copy is slightly decentered also, but not to the point where it starts bothering me. I might still send it to Pentax while I have my warranty though)
How to Check Your Lens for Decentering - Articles and Tips | PentaxForums.com
Thanks for the tip. I tested the lens as described here, and know that it is not exactly perfect at all corners. I realize that the corners will not be as sharp as the center, but some corners are sharper than the others. The most accurate test would be to photograph a wall that is precisely perpendicular to the camera using test charts.

The question is, what can be reasonably expected with any given copy of a zoom lens? What is considered to be a defect?
08-28-2017, 02:03 PM   #63
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QuoteOriginally posted by SSGGeezer Quote
What Steve said about the XR Rikenon is right there. I got one for under 15.00 and it is better than my skills at using it. Very nice images and the mount is metal, and as stated earlier, no contacts for A use. Green button metering, so fully manual.
I actually prefer the images from it over my M 50 1.7, which I may list in the sale forums in the near future.
Is there a difference between the Rikenon f2 and the f1.7? I have a Sears branded f1.7 and also the f2 which came on the lower end Sears/Ricoh in the eighties. The 1.7 has great qualities at f5.6-16. I have not used it wide open much.

Dan
08-28-2017, 08:58 PM   #64
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QuoteOriginally posted by DSLRnovice Quote
Thanks for the tip. I tested the lens as described here, and know that it is not exactly perfect at all corners. I realize that the corners will not be as sharp as the center, but some corners are sharper than the others. The most accurate test would be to photograph a wall that is precisely perpendicular to the camera using test charts.

The question is, what can be reasonably expected with any given copy of a zoom lens? What is considered to be a defect?
Well, it's not supposed to be decentred, just send it back - and send others back - until you get what you paid for.

Digitalis is very happy with his Sigma 8-16mm, but it took four copies and presumably a lot of unpleasant dealings with the Sigma dealer here.

08-29-2017, 09:21 AM   #65
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QuoteOriginally posted by clackers Quote
Well, it's not supposed to be decentred, just send it back - and send others back - until you get what you paid for.

Digitalis is very happy with his Sigma 8-16mm, but it took four copies and presumably a lot of unpleasant dealings with the Sigma dealer here.
Just tested the 28-105 again today with a better target. I realized that the proximity to the corner has to be close on all shots. When the target is closer to the edge on one shot than the others, those closer to the center will appear sharper especially since the test is at the widest aperture. There is no decentering with this copy.

The one thing that threw me off from the first lens comparison was that I accidentally compared a frame that was slightly off focus. Checking in the camera made this mistake easier. After viewing on the large screen it was more evident.

Dan
08-29-2017, 01:10 PM - 1 Like   #66
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QuoteOriginally posted by DSLRnovice Quote
Just tested the 28-105 again today with a better target. I realized that the proximity to the corner has to be close on all shots. When the target is closer to the edge on one shot than the others, those closer to the center will appear sharper especially since the test is at the widest aperture. There is no decentering with this copy.

The one thing that threw me off from the first lens comparison was that I accidentally compared a frame that was slightly off focus. Checking in the camera made this mistake easier. After viewing on the large screen it was more evident.

Dan
Great to hear, Dan - have fun!

08-29-2017, 03:16 PM   #67
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28-105 corner examples

QuoteOriginally posted by clackers Quote
Great to hear, Dan - have fun!
After looking at the decentering tests on the monitor, I can see some small variations. I would appreciate some opinions from you all if you think there is a problem here. The test I mentioned earlier was at 28mm and f5.6. At that point the corners were much sharper, and very similar. I had intended to use maximum aperture as recommended by the forum article, so I re-tested at f3.5. I suspect another copy might not be any better, but am not sure at this point. I don't think the local store has another on in stock, so changing lenses would not be so convenient.

Also note that I focused first with the telephone wires in the center of the frame. I did not refocus for the corners.
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08-29-2017, 04:42 PM   #68
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QuoteOriginally posted by DSLRnovice Quote
After looking at the decentering tests on the monitor, I can see some small variations. I would appreciate some opinions from you all if you think there is a problem here. The test I mentioned earlier was at 28mm and f5.6. At that point the corners were much sharper, and very similar. I had intended to use maximum aperture as recommended by the forum article, so I re-tested at f3.5. I suspect another copy might not be any better, but am not sure at this point. I don't think the local store has another on in stock, so changing lenses would not be so convenient.

Also note that I focused first with the telephone wires in the center of the frame. I did not refocus for the corners.
Have a look at the forum article by Beholder, Dan.

There are variations too in the 'good' Sigma at the bottom, using that method.

You can take shots of a focus chart that is exactly perpendicular, and take shots rotating the camera through 0, 90, 180 and 270 degrees.

If one side is decentred, that will also be rotated through the four individual images.

Softness by itself doesn't matter so much - there can be shutter shake, mirror shake if you're not using 2s delay, the corners themselves can be uniformly soft, there is field curvature, and of course, the corners are further away from the centre and hence not in the same plane.

But a decentreing defect will follow your rotation.

08-29-2017, 06:37 PM   #69
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QuoteOriginally posted by clackers Quote
Have a look at the forum article by Beholder, Dan.

There are variations too in the 'good' Sigma at the bottom, using that method.

You can take shots of a focus chart that is exactly perpendicular, and take shots rotating the camera through 0, 90, 180 and 270 degrees.

If one side is decentred, that will also be rotated through the four individual images.

Softness by itself doesn't matter so much - there can be shutter shake, mirror shake if you're not using 2s delay, the corners themselves can be uniformly soft, there is field curvature, and of course, the corners are further away from the centre and hence not in the same plane.

But a decentreing defect will follow your rotation.
To eliminate vibration I used both the 2s delay, cable release and LV with ES. I did look at the article and the sample of a 'good' Sigma. You are right the samples are not identical there. That is why I posted my samples for comments.

I am not sure what you mean by the decentering effect following the rotation.
08-29-2017, 06:54 PM   #70
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QuoteOriginally posted by DSLRnovice Quote
To eliminate vibration I used both the 2s delay, cable release and LV with ES. I did look at the article and the sample of a 'good' Sigma. You are right the samples are not identical there. That is why I posted my samples for comments.

I am not sure what you mean by the decentering effect following the rotation.
Well, if you think the left hand side is decentred, when you rotate clockwise the top of the pic should be soft, when you rotate again, the right hand side should go soft while the top clears up, when you rotate again, the bottom should soften but the right hand side sharpens back.

These are giveaways that either the front or rear elements are off-axis or tilted slightly.
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