Sigma 105mm Macro for portraits - help!

cblp

cblp

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Chris Harrold
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I recently bought the Sigma to try my hand at macro photography.

Initail macro shots were promising, even handheld. Some where a little soft but I put this down to not using a tripod and coping with the really narrow DOF.

Being 105mm and f/2.8 I thought it would also be great for portraits. So, with a sunny afternoon (rare) I took lots of shots of the kids in the garden. I put the camera in aperture mode and used a flash to fill the highlights. I experimented with different ISO (100-1000), WB and f-number (2.8-16). For a direct comparison I used the same settings with my 50mm f/1.8.

I was excited to see how sharp the 105mm pictures would be on the computer. Result; all the 50mm pictures were tack sharp, all the 105mm pictures were really soft.

Any thoughts? A bad lens, bad technique (most likely), bad AF (although it appeared to focus ok in the viewfinder), or is the 105mm macro not great for portraits?

I know the Nikon 50mm is a sharp lens but surely the Sigma 105mm should be just as sharp at f/11? Help! :bang:

Camera was a Nikon D80, although I doubt this has any bearing on the problem. Lenses were clean and I used the same settings for both.
 
the 105 macro is a belter of a lens,and is supposed to be very good for portrait work,although sigma aren't reknowned for their quality control,so you may have a lens that isn't quite right.as whats been said,post a pic or three up so folks can see,also look at the EXIF data to check focal length,shutter speed etc etc.....
 
I think if you are comparing the 50 to the Sigma, you are going to notice the difference in sharpness. The 50mm is very sharp, you may need to sharpen up the Sigma shots on the computer afterwards to get close and use a relatively fast shutter speed.
There is rule of thumb that says that you should not try to hand-hold a lens at a shutter speed less than 1/(focal length) which means for a 105mm lens speed should be over 1/105th ;) For the 50mm lens, anything over 1/50th should be ok. On the Sigma, I would try to keep about 1/200th or more and a wider aperture will give you a nice blurry background( less DOF)
But, saying that, my Sigma 105 produced really sharp shots and I rarely fiddled with them.
You really need to post a few results so we can see what your problem is.
Allan
 
Like an idiot I deleted the original pictures as they were NG.

Today, I tried a controlled test using the Nikon 50mm, my Nikon 18-200mm and the Sigma 105mm. I used a tripod with all lenses set at f/11 in A priority and ISO 400. I then did a 100% crop.

http://www.flickr.com/photos/chrisswiss/

When printed out the 50mm and 18-200mm (set at 95mm) are, to my eyes, exactly the same. The 105mm is worse, but no where near as bad as I was expecting. The difference is probably due to the quality of the ED Nikon lenses versus the cheaper Sigma.

So my conclusion is that the photographer screwed up! :thumbsdown: As I was in Aperture mode I didn't take any notice of the shutter speed. Probably it was too slow and the softness was just camera shake. I'll try again at the weekend but try manual mode instead, using the 1/(focal length) guideline.

Mind you, based on this test I'll probably stick to the Nikon lenses for portraits and just keep the Sigma for macro work.

Thanks for everyones comments.
 
Don't forget the crop factor when guessing the handholding shutter speed...

Better still, do your own test shots - start at 1/250th and work down in 1/2 or 1/3 stop steps to 1/60th. Have a look at some prints to see what speed YOU'RE happy with the results at. (BTW, that speed can change... If you're excited, shake will be apparent at a higher speed; if you're cold [or hot] shake can creep in. Practice and good technique can help. If you need extra speed, up the ISO - noise is easier to deal with than camera shake.)
 
here's a shot i took hand held last week...i think the shutter speed was 1/125th,and shot at F/11 and ISO100..

DSC01311.jpg


it had had no sharpening,and just a little boost in saturation..
 
Great shot. Way sharper than anything I've manged to get so far. Do you use a ring flash or off camera flash?

I noticed today when comparing the lenses that the Sigma shots were really underexposured compared to the Nikon lenses at the same settings. I think I need to get much more light on the subjects to get the best out of the lens, plus start thinking more about shutter speed.

Definetely a learning curve with this lens. But as they say, a bad workman always blames his tools :)
 
cblp said:
Great shot. Way sharper than anything I've manged to get so far. Do you use a ring flash or off camera flash?

I noticed today when comparing the lenses that the Sigma shots were really underexposured compared to the Nikon lenses at the same settings. I think I need to get much more light on the subjects to get the best out of the lens, plus start thinking more about shutter speed.

Definetely a learning curve with this lens. But as they say, a bad workman always blames his tools :)
Click to expand...

hi mate,and thanks.i used an off camera flash held by my wife,as the shot was hand held.this macro photography certainly takes some getting used too,and to be honest..the above shot is probably one of my most sucessful to date.as regards to under exposure...it's probably because you're holding the lens so close to the subject and casting a shadow..well,thats what i found anyway ;)
 
Thanks Nod. Some wise advice.
 
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