A lot of people swear off their lenses stating that the lens is soft wide open. Actually it's their technique that might be lacking. Of course a lens is going to be a bit softer at f1.8 than at f8, but there shouldn't be that much of a variation,
if you have a good lens. The problem is that at wide apertures the DOF becomes very shallow and the slightest little movement can throw your focus off. It's almost like shooting with a Super telephoto lens, if you sneeze the focus is off.
For shooting at wide apertures, unless you have nerves of steel, I would recommend using a tripod or a mono-pod. Especially if you are shooting indoors or in dim lighting situations. Even with a tripod the process of pressing down on the shutter with your finger can cause shake and blurry your picture. To avoid this you might try shooting with the mirror up, or using a shutter release, or
the self-timer. That way your finger, does not get in the way. When using a monopod, I recommend placing the monopod in between your two legs that way it acts as a third leg(same as a tripod), then pressing down on the monopod slightly(towards the ground), hold your breath and gently press on the shutter button. Another thing that can cause blurry pictures or "not-as-sharp pictures" especially when shooting wide open is believe it or not, removing the camera from your face too quickly after you hit the shutter button. Not sure why, but if you keep the camera still for 1 or 2 seconds next to your face after you hit the shutter button, the pictures seem to come out sharper(well at least with me).
The way I test my lenses is not by some ridiculous charts and complicated graphs as do the pro reviewers(although I read these too) . I use a simple calendar hanging on my wall with large and very small lettering almost like the charts you use when you go see an eye-doctor. if you can find a calendar with shadow lettering the much better, because bad lenses have trouble making out the subtle shadows in the lettering. Then from about ten feet, I take a series of pictures from the lowest to the highest aperture. Sometimes I have to repeat this 2 or 3 times or more, to make sure it wasn't my technique that ruined the picture, or gave me a wrong impression. When satisfied, I compare these results under the same lighting and conditions with one of my better lenses.
Of course sharpness is not the only thing in a lens. There are other things like color rendition, micro contrast, character, pixel dust etc.. Unfortunately using a monopod or tripod is not always convenient or appropriate, but don't blame the lens if your pictures come out soft...
Last edited by hjoseph7; 08-06-2017 at 11:55 AM.