Lens sharpness

[elmo_2006]

'cool beans'


[]

[Jon Ruyle]

On the subject of questioning the sharpness ability of a given lens, I have seen many posts everywherethat state the testing procedures is to use live view via a tripod alongside other variables. In my humble opinion I cannot understand how this may solve the issue of softness or sharpness or some other IQ concern that may have been raised.

Mark is right- I suggested manual focus with live view to remove autofocus from the equation, and because it is impossible (at least for me) to judge focus with the viewfinder.

i.e., taking a photo via the viewfinder, the images seem to be questionable, however using liveview to perform testing the IQ has somewaht improved, what has this really proved?

If I couldn't get a sharp image using manual focus with the viewfinder but could get a sharp one with live view, I would conclude that the problem is my inability to judge focus through the viewfinder, not a fault of the lens (though maybe the viewfinder diopter thingy just needs adjustment). If I couldn't get a sharp image using autofocus but could get a sharp image with manual focus + live view, I would conclude that the autofocus is the problem.

[Colin]

My best quick test, stolen from this forum....


Takea picture of a ruler with a very slight offset, with center autofocus point selected (or another point if you want to test another area of the lens). One side of the ruler shouldbe slightly father awaythan the other (from the camera) Take the picture with a tripod (and mirror lockup enabled if you don't have a really fast shutter speed). If the camera/lens combination is back/front focusing, with 100% view you'll see the lines to the left or right more in focus than the lines on the autofocus point. Regardless, you'll have something in focus which will identify the focal plane, and show you how sharp the lens is in that area. If everything is really blurry, it's just soft. If it's blurry at the autofocus point, but not a little behind/in front of that point, the camera/lens combination needs calibration, unless you've got a 50mm f/1.2L using it at f/2 or f/2.8, or whatever, in which case, that's just the way it is, and you have the same issue which made me sell it.


In my experience, using sharpness of 2-3 in DPP should yield very good results in getting sharp detail in the focal plane.

[Stephen Probert]

Peter, I agree with a previous poster that you are focused on the seatbelt in the first picture and on the statue in the second. You need a narrower aperture to get the face in focus and the background of the second image. Include aperture and shutter values, please. Also, web-compressed pictures will not show if it is sharp very well. 100% crops would be better.

[piiooo]

Im really concerned that my canon 17-55 F2.8 isnt giving sharp enough images any views please

Hey there,


It looks to me that you shot wide open or almost wide open. On the first picture, the baby's seatbelt is quite sharp, so this area must have been focused on. On the second picture, parts of the pillar are in focus. It is still possible that the lens is not sharp, but, IMHO, I think we have setting relatedissues here. I would focus on baby's closest eye, and just this aloneshould increase perception of sharpness. Also, thef number can be stopped down to, say,4 or 5.6, so the whole baby is in focus. The tradeoff would be less blurry background. When taking the second picture, I would focus on the pole (like it already is) but step down to about 8-11. This will increase depth of field some more. Stepping down more will increase diffraction which also affects sharpness. If small aperture increases exposure time beyond handholding capabilities, cranking up ISO or using a tripod is the way to go. I am not sure how familiar you are with terms aperture, exposure time, depth of field, hyperfocal distance, diffractionetc, but if you are not it is time now. If youknow all about those thingsandthe lack of sharpnessis the lens' fault, then please do not get offended.What I wroteis based on myimpression and limited experience.Take care

[piiooo]

Oops it looks like some other members beat me already. Well, I quess you get another opinion[]

[peterborough_photography]

I think your right, Im shooting far to open.


Maybee being to lazy and hopeing the open lens will compensate for the quality of light or lack of it.





I think I have being shooting open all the time as this lens really does do wonders in poor light, I need to use the camera a little more and you guys have really confirmed I need to be more pro-active and not rely on the lens doing all the work.





I will how ever do some tests perhaps with a ruler just to gauge my lens. :-)