OS Worthwhile?

[Superangel]

Hi everybody

I've had the Sigma 17-70 2.8-4.5 as a walkabout lens on my 500D for the last few months, but I've noticed that without a tripod a lot of my shots are slightly blurred (zoomed out they look fine, but at 100% it's very noticeable).

I love this Sigma lens, it's well-built and generally produces nice shots, but I was wondering: is it worth upgrading to the new Sigma 17-70 2.8-4.0 OS HSM lens? I don't have any experience with stabilized lenses, but given my hands are generally quite shaky, would it help?

I generally shoot portraits, macro shots, and the occasional landscape. For macro and landscapes, I use try to use a tripod, but it's the handheld portrait shots that I really want to make sharper.

Thanks for your help!

[TheObiJuan]

OS will not make a soft, consumer lens sharper.
OS will not make motion bur non-existent.
OS will not help as much--in that focal range--as increasing the ISO to get higher SS.

If it's portrait lenses you want, why not consider the 85 f/1.8? Limited range--especially on a cropped body--but sharp wide open and outstanding background blur for a consumer lens.

I'd post some examples with EXIF intact to see if they are blurred or soft.
I think you just need to stop down a few stops to get optimal sharpness with that lens. This compounds the problem, since you shutter speed drops as a result.

[Superangel]

Thanks, TheObiJuan.

To be honest, I'm a little lazy to carry around different lenses, so a versatile walkaround lens is better for me than a portrait prime, even if it means making some sacrifices.

I'll try your tip about the ISO, as I guess I'm a little weary of noise. As for samples, I'll try and find a few, but normally this Sigma is very sharp when mounted on a tripod, so I suspect it's my shaky hands or the subject moving slightly.

[Superangel]

Attached are some 100% crop samples, and the EXIF is below (all were handheld shots, in aperture priority mode, in cloudy daylight):

Example 1: f3.5, 1/50, ISO100, 28mm
Example 2: f4.5, 1/125, ISO100, 57mm
Example 3: f4.0, 1/200, ISO100, 48mm

I'm still fairly new to DSLRs, so I won't pretend my focusing is always 100%, but each image looks fairly soft. However, mounted on a tripod, this Sigma lens can be really sharp, so I'm not sure what to try next.

Any advice would be welcome, as I don't want to splash out on a new lens unless it's really necessary :)

[Prospero]

The 17-70 is indeed a really sharp lens provided your shutterspeed is fast enough and you get it focussed right. Although it has its flaws (mainly slow and inconsistend autofocusing on my Nikon), a lack of sharpness is hardly one of them.

Its hard to tell from your shots whether the softness is caused by camera shake, subject movement or missed focus. Given the settings you used, I guess the first shot is caused by a combination of a subject movement and camerashake. The same goes for the second shot.
I think with the third shot you missed focus, because the nose seems sharper than the eye.

Anyway, upgrading the lens won't help. Just raising your ISO so that you will get a faster shutterspeed will help in these situations.

[TheObiJuan]

Use a tripod to take a picture of a newspaper taped to the wall.
Take one photo wide open, one at f/8.
Once focus is achieved, set focus to manual and don't move it.

This will take motion blur out of the equation.

[Superangel]

Thank you both, I really appreciate your help :)

I'll try the setup you described and post the results later on.