check my lens....

[gpc1]

Hi,

I have been convinced that my sigma was a soft copy, however, this may be down to user error after looking at the below.

Wouls you mind giving your opinion as to whether you thisk these are sharp or on the soft side.

http://www.talkphotography.co.uk/gallery/data/500/-4089.jpg

http://www.talkphotography.co.uk/gallery/data/500/-4088.jpg

http://www.talkphotography.co.uk/gallery/data/500/-4087.jpg

http://www.talkphotography.co.uk/gallery/data/500/-4091.jpg


Much appreciated

Greg

[Raymond Lin]

Pics too small to tell.

Need 100% crop

[Ant]

What lens is it?

[gpc1]

sigma 17 70 apo dg

Ok, Will post 100% crop once ive wroked out how....

[gpc1]

How about this, not sure its 100% but its a crop...

http://www.talkphotography.co.uk/gallery/data/500/-40891.jpg

[gpc1]

or this.. these crops were 1/400 @ f10

http://www.talkphotography.co.uk/gallery/data/500/1-4089.jpg

[CT]

These sorts of test are absolutely meaningless unless the camera is set up absolutely square to the subject, which needs a tripod and a very careful setting up.

[gpc1]

well, i was pretty square on to the subject, about 1 ft away, may be a little more. Decent sunlight, hand held resting carefully on a table. It wasnt just a point and hope job.

All im asking is, given the above, would this crop be considered sharp or soft. being relativley new and not having experienced many different types of lenses i was just after an little guidance as to whether the softish shots i was getting were my fault or the lens not being a good copy.

I will set up the tripod later and get something more 'scientific' set up.

thks
Rgds
Greg

[EdBray]

Best thing to do is bluetack a broadsheet newspaper to the wall, set your camera up on a tripod completely square to it and shoot at various focal lengths and different apertures. If you do not have a cable release, use the self timer, this will diminish the chance of camera shake.

[CT]

Yep newspaper is good or even a plain old brick wall has lots of detail and texture. Hand holding you only have to have the camera tilted by a fraction of an inch to throw everything out.

[theory]

Were these shots at F/10? I would be trying wide open (usually a tad soft, but for a benchmark worth doing) and a couple of stops down from that as that way other people will be able to compare better I expect.

F/10 is always going to be sharp really.

[EdBray]

If a zoom, I would take shots at the widest setting, two middle settings and the shortest setting, I would take each length at open aperture, two stops down and 4 stops down, would not usually take shots at f22 or f32 as these are likely to suffer some distortion, although as digital film is cheap may be worth trying fully closed to see how the lens performs. The more you know about how your lens performs, the better you will use in when it's required.

[strobemonkey]

Testing only one lens is actually inconclusive of its overall shaprness. If you have two of the same lenses, set with the same settings and subject, then you can judge sharpness using one good lens as a control.

just my own opinion though.

[gpc1]

OK....


Could someone do me a favour then and post a shot, straight out of camera using their sigma 17 70 to give me a rough idea of quality.

I would think it would be pretty easy to see sharpness in a lens. Alternatively if you could go to my flickr page and look at the 'freddies second birthday' set of shots and give me your thougts on sharpness.

http://www.flickr.com/photos/23064358@N02/sets/72157605073102416/

baring in mind these will have been processed and sharpened in lightrooom as much as possible.

When i view them in large im not happy with the sharpness but I have nothing for comparison so i dont know if its me, my lens or both.

the attached shots in this thread look pretty sharp to me, but im fairly new to this so not sure what to expect of this lens.

Thanks for help

Greg

[allanm]

I had a look at your birthday shots, but its very difficult to tell if there is a problem. What focus settings were you using.
In pic 3909 for example, the childs face is a little soft but the neck of the T shirt is sharp as sharp.
In pic 3766, the girls face is soft but her arm and the decking in front is sharp.
It may be just an issue with selecting the correct active focus points in the auto focus area.
Allan

[gpc1]

Cheers Allanm
Good points there, never really noticed that.
I only ever use the centre focus point and then re-frame...perhaps that is where im going wrong.