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06-29-2017, 09:49 PM   #1
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Is this Normal for HD DA 20-40?

Hello,

I might be paranoid, but I am wondering whether these shots from my HD DA 20-40 shot at 40mm and f6.3 look right? The shots were taken on a rainy day and my K-S2 was set to ISO 500.

Full image:





100% crop:





And my lens looked like this (X-posted in My HD DA 20-40 Doesn't Look Right - PentaxForums.com), the front barrel seems to be not straight, but to one side.



06-29-2017, 10:22 PM   #2
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Mine was producing similar image until I did focus adjustment on my camera. I needed +5 in my case. Also, I find that first focus confirmation tend not to be complete in focus and it would readjust itself a bit and then it is spot on. I don't know how 'normal' that is. (Edit: actually this is true only because I'm always in AF.C mode. AF.S doesn't seem to have this problem.)

But if the barrel isn't even straight, you should be able to see uneven sharpness if shooting something flat.

Last edited by ruggiex; 06-29-2017 at 11:08 PM.
06-29-2017, 11:41 PM   #3
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ISO 500 may not be enough for subjects which might move, or maybe your own movement, especially in low lighting. You have to keep track of your shutter speed in that situation. Before making a focus adjustment it is necessary to run a proper focus test.

The barrel should not be crooked. If you bought the lens recently, I would say return it for replacement. Otherwise, send it to Pentax to have it examined.
06-29-2017, 11:53 PM   #4
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QuoteOriginally posted by mikesbike Quote
ISO 500 may not be enough for subjects which might move, or maybe your own movement, especially in low lighting. You have to keep track of your shutter speed in that situation. Before making a focus adjustment it is necessary to run a proper focus test.

The barrel should not be crooked. If you bought the lens recently, I would say return it for replacement. Otherwise, send it to Pentax to have it examined.
The train was pulling out, and I used TAv to fix shutter at 1/640s and aperture at f6.3. The camera have chosen ISO 500 on itself.

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---------- Post added 06-29-17 at 11:54 PM ----------

QuoteOriginally posted by ruggiex Quote
Mine was producing similar image until I did focus adjustment on my camera. I needed +5 in my case. Also, I find that first focus confirmation tend not to be complete in focus and it would readjust itself a bit and then it is spot on. I don't know how 'normal' that is. (Edit: actually this is true only because I'm always in AF.C mode. AF.S doesn't seem to have this problem.)

But if the barrel isn't even straight, you should be able to see uneven sharpness if shooting something flat.
I have used AF.A central point only, with back button focus. And I always shoot prefocus with the smallest possible aperture.

通过我的 Nexus 6P 上的 Tapatalk发言

06-30-2017, 06:19 AM   #5
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QuoteOriginally posted by butangmucat Quote
I have used AF.A central point only, with back button focus. And I always shoot prefocus with the smallest possible aperture
Lenses have variation. If the focus is off, small aperture may or may not hide it that's why focus adjustment exists.
06-30-2017, 02:57 PM   #6
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I don't have the 20-40, but if this is normal, this is sure not a good advertisement for that lens. There are of course quite a few variables that you've not mentioned that may have an impact on IQ: Train speed - what speed is pulling out?; Was this taken through a dirty window? What about the air conditions - the background looks possibly quite foggy, which can impact IQ in a large way. (Rain can also.) The lens barrel looks bad to me and I'm thinking the entire lens needs repair, or just to be replaced. If it was a focus adjustment, one could check to see if anything in the photo is in focus - is it? Or does it all look like that. How do other photos look - different day and subject? Do they all appear similar? My gut tells me you are NOT paranoid, and that one or more things are notably off.
07-09-2017, 08:57 AM   #7
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To me it doesn't look like a focus issue but the metering!. Is the camera metering system set to spot metering?, If so change it so it meters the whole frame. Everything seems in focus, maybe not perfect but I find continuous focus while using the back AF button helps with focus. The weather looks pretty grey and its hard to pretty that up on the best of days... I own the 20-40 Ltd and its Amazing, I feel like I have a secret weapon because it gets bad press for its focal length, aperture and price, which has dropped down considerably!....Cheers
07-09-2017, 10:03 AM   #8
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QuoteOriginally posted by butangmucat Quote
The shots were taken on a rainy day
all lenses performs badly on a rainy day.
come on, some people complain that gear review websites are useless since studio/laboratory conditions are not real world photography, but your test is too much real

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