Lens or User problem?


koren

New Member
Aug 25, 2009
8
0
0
#1
I've recently bought the Pentax SMC-M 50mm F1.7 lens from a forumer. But the photos were not quite sharp at F1.7. It turns out better at F4 or smaller. I dont know if its the lens issue or my settings. can anyone advise?
F4

IMGP0335 by Li Shixian, on Flickr
F1.7

IMGP0334 by Li Shixian, on Flickr
 

rhino123

Moderator
Staff member
Sep 1, 2006
5,243
15
38
NA
#3
Most, if not all, lenses are not at their optimal sharpness wide open... plus as the aperture is wider, the DOF is shallower, so onlycertain portion of the over image is in focus, others are off focus.

So it also depend on where you are focusing on.
 

ZerocoolAstra

Senior Member
Mar 13, 2008
9,522
0
0
rainy Singapore
#4
I've recently bought the Pentax SMC-M 50mm F1.7 lens from a forumer. But the photos were not quite sharp at F1.7. It turns out better at F4 or smaller. I dont know if its the lens issue or my settings. can anyone advise?
F4

IMGP0335 by Li Shixian, on Flickr
F1.7

IMGP0334 by Li Shixian, on Flickr
The 'P' in Pentax looks sharp enough. I presume that's where you were focusing, coz that's roughly in the middle of the photo.
But the bokeh.... much to be desired...
 

pinholecam

Moderator
Staff member
Jul 23, 2007
10,933
85
48
#5
Most lenses are not as sharp wide open and will have less contrast too.
The area around 'PEN' looks sharp enough, remember that you are dealing which very shallow DOF too, so not all the letters can be as sharp.
Use a hood to get minimize loss of contrast (Note : this is not a cure-all, just to maximize what is possible)
 

xtunbox

New Member
Jul 5, 2010
194
0
0
#6
Photos look under exposed to me and the environment maybe too dark for you to properly manual focus. Maybe you can try repeating the whole "experiment" again with sufficient light and with a stable tripod.
 

yrh0413

New Member
Oct 21, 2004
1,793
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0
Singapore
www.danielyee.net
#8
doesn't look like handshake to me, the fonts are sharp... this looks more like ghosting/ lack of contrast at wide aperture which is pretty normal for most large aperture lenses.
 

stunna88

New Member
Apr 3, 2009
310
0
0
#9
The first sample is normal, at f1.7 DOF is super shallow anyway, at least the part u're focusing on is still sharp.

The second sample at f1.7 is a too hazy...looks like ghosting but there is no direct light source. Not sure why.
 

ZerocoolAstra

Senior Member
Mar 13, 2008
9,522
0
0
rainy Singapore
#11
Hey.. thanks everyone for the help... after playing around with the lens today, i found that F1.7 would focus on a really small point. F2.8 onwards would have a shallower DOF. Having fun with the lens now..
You mean deeper DOF?
Your outdoor photos look pretty sharp.
 

Daoyin

Senior Member
Nov 25, 2008
2,808
6
38
West
#12
doesn't look like handshake to me, the fonts are sharp... this looks more like ghosting/ lack of contrast at wide aperture which is pretty normal for most large aperture lenses.
The fonts do look sharp enough. I stand corrected.
 

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