Trying to Macro with a sigma 70-300 APO, not much joy though

wildman · 6 Feb 2012 at 22:27

Its driving me nuts. It looks like I have a crisp sharp image in the viewfinder, then when I get the pictures back to the PC there is always something slightly out of focus.

e.g I was macro shooting some daffodils, the centre was razor sharp but where the petals were slightly back they were some what out of focus.

I was at a focal length of 300 with macro switch on lens flicked to on. Was using F5.6. I guess I need to increase the DOF and maybe raise F to around 11 ?

Also I have to stand crazy far away from the subject to get it focused in the begining ? SHould I thnk about maybe investing in some extension tubes and using the kit 18-70 lens instead

Nexus · 6 Feb 2012 at 22:29

Could try shooting tethered to a laptop.

Ksanti · 6 Feb 2012 at 22:43

Yeah a 300mm lens even at the Sigma's MFD will give very shallow DoF. You'll need to look at a tripod/flashgun to really have a feasible chance of getting good shots with it except in really bright daylight.

wildman · 6 Feb 2012 at 23:38

Ksanti said:
Yeah a 300mm lens even at the Sigma's MFD will give very shallow DoF. You'll need to look at a tripod/flashgun to really have a feasible chance of getting good shots with it except in really bright daylight.

Was already using a tripod. Flash gun is something I need to invest in, the built in one on the A200 is weak sauce.

Do you think I would yield better results by investing in a set of the kenko extension tubes and possibly using either my 50 f1.8 or maybe even the original kit lens ? Not sure if I am ready to part with 400 notes for a dedicated macro lens just yet

D.P. · 7 Feb 2012 at 00:03

Your problem is solely down to lack of DoF.

For sure you will need a good tripod and head, plus macro flash to really get very far, but you need to shoot at f/16 or so.

Really you need to do focus stacking if you want a sufficiently large DoF to get soemthing small to be completely in focus.

The Dof is purely a function of magnification ratio and aperture. It doesn't matter what lens/focal length/extension tube/focal distance you are using, if you magnify the subject to the same image proportion then you will get the same DoF a the same aperture.

wildman · 7 Feb 2012 at 00:43

D.P. said:
Your problem is solely down to lack of DoF.

For sure you will need a good tripod and head, plus macro flash to really get very far, but you need to shoot at f/16 or so.

Really you need to do focus stacking if you want a sufficiently large DoF to get soemthing small to be completely in focus.

The Dof is purely a function of magnification ratio and aperture. It doesn't matter what lens/focal length/extension tube/focal distance you are using, if you magnify the subject to the same image proportion then you will get the same DoF a the same aperture.

Sorry for the dumb question, but what exactly is focus stacking ? Is it taking multiple shots at different DoF and then adding them together say in PS ? WOuld this be as simple as simply taking multiple shots at differetn F settings and then putting them altogether ?

Sorry I am new to macro photography

greywolf · 7 Feb 2012 at 01:36

Basically manual focus at the front of the subject, take a shot, then move the focus forwards a tad and take another, and so on, until the whole subject has been covered. Then use a program to combine the shots. I've used Helicon Focus in the past.

Andy90 · 7 Feb 2012 at 15:15

As others have already said, with Macro photography, the depth of field at close distances can be fractions of a milimeter. Very difficult to get everything in focus unless shooting at small apertures. Smaller apertures, result in slower shutter speeds, which often results in camera movement = blur!

Some tips.

Zoom lenses with Macro printed all over them aren't macro lenses. They're zoom lenses with a close focus ability, by their very nature Zoom lenses are compromises optically.

Prime lenses, such as 50mm or 100mm are usually very good optically. Coupled with some extension tubes they can result in some great shots.

Dedicated Macro lenses - although expensive they're usually some of the sharpest optics a manufacturer will make.

Tripod - get a good sturdy tripod - will keep the camera still

Remote release - allows you to fire the shutter without touching the camera - minimises vibration through the camera

Mirror lockup - Some digital SLRS allow you to lock the mirror up and give a live view on the display screen

Live View - use it to manually focus on the subject.

Autofocus - Turn it off - use manual focus.

Focus Stacking - Read this > http://en.wikipedia.org/wiki/Focus_stacking