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Samyang 14 mm f/2.8 IF ED UMC Aspherical
#1
I've been testing this lens to see if it's as sharp as tests report it to be. But I'm not getting this sharpness.



I've checked focus with live view, and I think I have it at its sharpest position, but it's hard to be sure, due to the enormous depth of field (hyperfocal distance is 3.32 meters, focus is from 1.66 meters <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/tongue.gif' class='bbc_emoticon' alt='Tongue' />).



The test here at Photozone says it's sharp from 2.8 on the Canon EOS 50D, I have the Pentax K-5 and it's only 1 megapixle more or so, so it shouldn't be much softer at 100%.



Is there something wrong with it, or am I doing something very wrong? I've tried other focus distances, but it's not getting better.



Here are some images, the start from f/2.8, then f/4 and so on:

- https://www.dropbox.com/sh/xlhylu0iqgpfqnv/5943ecQMDd



They look OK from F/4 and up I think, but isn't f/2.8 supposed to be sharper? I have tested several times, there's no better than this at f/2.8.
#2
Don't trust the distance scale!

Looking at your images the focus point seems to be very close.



Set your lens to f/2.8, then do magnified live-view. Then stop down.
#3
I checked the focusing scale, and the focus ring stops where it seems like it's supposed to stop. I focused for the f/2.8, then took the picture, then stopped down for the other shots with the same position on the focus ring.



http://www.youtube.com/watch?v=V89H8JYw9_8





When I've also tried focusing with live vview, but even at f/2.8, the depth of field is huge, so it's hard to know when it's at its sharpest. Specially since the K-5 can't magnify up to 100%. Beyond 4x is wasted magnification IMO.
#4
[quote name='AlexanderE' timestamp='1349719596' post='20539']

I've been testing this lens to see if it's as sharp as tests report it to be. But I'm not getting this sharpness.



I've checked focus with live view, and I think I have it at its sharpest position, but it's hard to be sure, due to the enormous depth of field (hyperfocal distance is 3.32 meters, focus is from 1.66 meters <img src='http://forum.photozone.de/public/style_emoticons/<#EMO_DIR#>/tongue.gif' class='bbc_emoticon' alt='Tongue' />).



The test here at Photozone says it's sharp from 2.8 on the Canon EOS 50D, I have the Pentax K-5 and it's only 1 megapixle more or so, so it shouldn't be much softer at 100%.



Is there something wrong with it, or am I doing something very wrong? I've tried other focus distances, but it's not getting better.



Here are some images, the start from f/2.8, then f/4 and so on:

- https://www.dropbox.com/sh/xlhylu0iqgpfqnv/5943ecQMDd



They look OK from F/4 and up I think, but isn't f/2.8 supposed to be sharper? I have tested several times, there's no better than this at f/2.8.

[/quote]
#5
Hi,

Looks close focussed to me,at F2.8 the whole image is not going to be sharp.For checking sharpness I'd focus on infinity with liveview.



Dave's cliches
#6
[quote name='dave's clichés' timestamp='1349767082' post='20543']

Hi,

Looks close focussed to me,at F2.8 the whole image is not going to be sharp.For checking sharpness I'd focus on infinity with liveview.



Dave's cliches

[/quote]



Just ignore the distance scale here. My samples where "way beyond infinity" when setting the focus to infinity according to the scale.
#7
But I've written that already. I have checked with live view, it doesn't get sharper. And, even if my focus scale seem to be placed correctly (as it stops in both ends where the scale stops), should I still ignore it? I Have to check it with a measuring tape.
#8
[quote name='AlexanderE' timestamp='1349775798' post='20546']

But I've written that already. I have checked with live view, it doesn't get sharper. And, even if my focus scale seem to be placed correctly (as it stops in both ends where the scale stops), should I still ignore it? I Have to check it with a measuring tape.

[/quote]





Yes, if the focus scale is not right, it does not matter if it stops at both ends, because the ends are wrong, if the focus scale is adjusted wrong. The scale (i.e. the distance between the numbers) is correct, however, how the scale matches the actual distance could be wrong depending on how the lens is adjusted when it was assembled.

Here is information for example how it affected my Samyang 8mm fish-eye, and how it could be corrected: http://photonius.wikispaces.com/Fish-eye...+Stitching

Since you seem to have an issue with focusing even in liveview (on my canon it seems to work quite ok with 10x), I recommend you set the camera on a tripod, measure an object say at 3 meters or 5 meters (e.g. newspaper), and just shoot through the whole distance scale. Later, on the computer you choose the best image, and you should know at what setting you shot it, and then you will see if it is off or not.



So, having said that, the first three pictures (which I presume are f2.8, f4 etc.) don't look too far off. If you look at the church tower, it's not too bad, but as you say, it's obviously softer at f2.8. Well, first check how far off your focus scale is. If it is off, redo the shots with estimated corrected distance (you can take a series of shots, with slight changed focus each time).

Perhaps there is also an issue with the lens, it does look a bit softer on the right side, perhaps some decentering, which may affect general sharpness as well?
#9
I will be using a measuring tape and objects at various distances for a test, and then see how it turns out.



But I find it odd that if the focus ring starts and stops at the correct places, that it would be wrong. Wouldn't that indicate that the markings on the ring are in the wrong places?



I'll check your link.



Thank you for the reply, the others as well.
#10
What I suspect is happening on the scale is that as they make the same lens but just change the mount for different cameras, and they might not have taken enough care to get the spacing exactly right. So you end up with an extension tube effect on the focus range. For example, on my fisheye as I got it, focus was much further out than indicated. By loosening some screws you can align it to the scale which also gave me the specified near focus range too.
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