My macros have gone soft!!!!

growse · 8 May 2006 at 18:26

Ok, went on a shoot yesterday (in more ways than one...!) and took around 80 images of people shooting clay pigeons. Camera is a 350d and the lens for the day was a Sigma 24-70 EX DG jobbie. It's about 4 months old and I've not usually had any problems with it.

Most of the shots came out fine - here's a 100% crop of a trap at f5 and 70mm:

Not a problem. The problem was with all of my macro shots of the day. I took all of these at 70mm and f2.8, and using autofocus. Here's an example of a macro at 100%:

Bad. Very bad. All the macro ones at 70mm and 2.8 were like this. I don't think it's camera shake, as that one is at (from memory) 1/400. Just to prove that it's possible only macro shots - here's a far-away shot at f2.8 and 70mm. I know it's ISO800, but it's not particularly blurry, and in low light and hand-held, that could just be shake. Crude, but maybe proves that point:

So then I tried a macro. It's ISO 1600, but came out not too bad, which proves the lens isn't that bad when it does macro stuff:

Therefore, there's a number of posibilities:

1) The cold/light drizzle made the lens not focus properly on macros.
2) For every single shot, I focussed, then moved.
3) There's a temperamental fault with the lens
4) I'm insane.

Any thoughts as to which of these it could be?

Gamefreak501 · 8 May 2006 at 19:10

You should go back to where you took those photos if you can and see if you get the same result when the weather conditions are better. Then you should do more testing with other subjects.

That will tell you what kind of scale the fault is and under what conditions it might show itself (maybe it's the f number that doing it). However...if the lens doesn't perform like it should...that would be grounds for me to get a replacement from Sigma, I like all my lenses to be 100%, although some still suffer from CA, especially my 75-300, but they are all old lenses and have no warranty of any sort.

wez130 · 8 May 2006 at 22:01

also try shooting at around F/5.6 - F8 for sharper images

growse · 9 May 2006 at 11:02

Hmmmm, it's difficult to go back as it's a bit of a trek. I know f5-8 is sharper, but didn't have a tripod that day with me so was keen on keeping the aperture quite wide. I don't want to go through the faff of returning it and being without it for 6 weeks if it's just mistakes by me rather than a faulty lens.

wez130 · 9 May 2006 at 13:10

with the largest focal length of 70mm, you could easily have shot at ISO100, F/5.6 and a time of 1/70s with no risk of camera shake, i take shots at 1/30th of a second on my 300mm with unnoticable shake but i have a steady hand anyway.

What i'm saying is as a general rule, you can shoot at the equivelent lengh of your lens in milliseconds, eg, at 100mm, you can usually shoot at ~ 1/100th of a second with no shake, at 300mm, a time of 1/300th of a second is recommended, at 30mm, then a time of 1/30th of a second etc etc.

growse · 9 May 2006 at 13:34

Point taken. I never really took much notice of the shutter speed if it was fast enough. Also on macro shots I tend to go after the small depth of field for some good effects. I'll keep doing shots with it to find out where I'm going wrong.

wez130 · 9 May 2006 at 19:29

growse said:
Point taken. I never really took much notice of the shutter speed if it was fast enough. Also on macro shots I tend to go after the small depth of field for some good effects. I'll keep doing shots with it to find out where I'm going wrong.

you'll still get quite a narrow DOF at F/5.6

SDK^ · 9 May 2006 at 19:41

growse said:
Point taken. I never really took much notice of the shutter speed if it was fast enough. Also on macro shots I tend to go after the small depth of field for some good effects. I'll keep doing shots with it to find out where I'm going wrong.

You realise that the closer you get to your subject the narrower the depth of field.
At F2.8 you will only get a few millimeters in sharp focus.

growse · 9 May 2006 at 21:53

SDK^ said:
You realise that the closer you get to your subject the narrower the depth of field.
At F2.8 you will only get a few millimeters in sharp focus.

I actually didn't know that. I suppose I've been trying to get a tiny depth of field to get that authentic "macro" look, but I realise that it's possibly more about what's in focus as opposed to how small the DOF is.....

SDK^ · 9 May 2006 at 22:27

With proper macro lenses and photography you will struggle more trying to maximise depth of field than reduce it.
Even F11 isn't really enough and past that you really need more light.

This was an example I took a couple of years ago at F5.6 - It demonstrates the small depth of field.

Sleepyd · 9 May 2006 at 22:37

SDK^ said:
With proper macro lenses and photography you will struggle more trying to maximise depth of field than reduce it.
Even F11 isn't really enough and past that you really need more light.

This was an example I took a couple of years ago at F5.6 - It demonstrates the small depth of field.

I suppose it's even worse with a 5D