Big or small

Harald · Post by **Harald** » Thu Oct 20, 2011 7:23 am

Hi there,
which is best ?
Big aperture, a lot of stacks or small aperture, few stacks ?
I have the Canon MP-E65. Big stack with f2,8 or few stack with f11 ?
I use the Zerene Stacker.

ChrisRaper · Post by **ChrisRaper** » Fri Oct 21, 2011 1:04 am

I don't have the MP-E 65mm but my understanding is that the lens needs to be set at whichever aperture is the 'sweet spot' for that lens, in terms of clarity. Using too wide or too narrow an aperture leads to less clarity in the final picture. For the MP-E I think f8 is a good starting point so then work out how narrow your depth of focus is and then from that you'll know how many stacks you need

rjlittlefield · Post by **rjlittlefield** » Fri Oct 21, 2011 1:13 am

Sweet spot is right, but the sweet spot depends on magnification.

At 1:1, it may be around f/8. But at 5:1, it is much wider, more like f/4.

See for example http://www.photomacrography.net/forum/v ... =9757#9757

--Rik

ChrisR · Post by **ChrisR** » Fri Oct 21, 2011 1:29 am

Apart from the usual recommendation that you try it

:

For higher resolution, use wider apertures, though you may find that your particular lens is best stopped down a stop or so from maximum. It will also have characteristic regarding its edge sharpness relative to centre at different apertures, etc. If you look at the forum users' photos, f/2.8 and f/4 are popular for higher magnifications.

To avoid diffraction softening on your 7D, try avoiding effective apertures smaller than about f/22.
Effective Aperture is given (approximately) by
EA =Aperture on lens x (Magnification+1 )
So you'd get about f/22 or more from or smaller than a marked f/11 at 1:1, but f/4 at 4:1.

That's for highest possible, theoretical sharpness.
If you're only going to use the pictures for 1000 pixel wide images on a computer screen, try a couple of stops smaller and you probably won't see any difference at all, and will have far fewer pictures to take.

Edit: Error corrected

abpho · Post by **abpho** » Fri Oct 21, 2011 9:15 am

ChrisR wrote:EA = (Aperture on lens+1 ) x Magnification

Correct me if I am wrong, but I think you meant to say
EA = (aperture of lens) x (magnification + 1)

ChrisR · Post by **ChrisR** » Fri Oct 21, 2011 1:56 pm

abpho wrote:
ChrisR wrote:EA = (Aperture on lens+1 ) x Magnification
Correct me if I am wrong, but I think you meant to say
EA = (aperture of lens) x (magnification + 1)

Indeed - thanks!