100mm f2.8 Macro : Center not sharp as apearture increase?

[vinwin]

Hi macro expert,

I just got myself a EF100mm f2.8 macro lens. This is the 1st time I own a macro lens. Did some test shots at home with tripod mount, cable release and mirror lock up. The following are the results as I increase the apearture from f5.6 to f8, f11, f16, f22, f29 and f32.

1. The center getting sharper as i inrease the apeature from f5.6, f8, f11 and f16, After f16, the center sharpness amd contrast start to drop.

2. At the corner, the shaprness and contrast increase as I increase the apearture from f5.6 all the way to f29.


Is this the normal? Is this the characteristic of a maco lens? It's seems like the peak performance of this lens is at f11 to f16.

Someone says that this is called Diffraction softening due to small apertures. The DOF increases the images become softer with smaller apertures.

There is a good description of what is on this Diffraction softening
http://www.cambridgeincolour.com/tut...hotography.htm

Is this truth?

Thanks

[calebk]

Yes it is. You've already found yourself the answer, haven't you?

[Headshotzx]

Uh, not a pro or a macro-shooter, but I believe that if you're increasing the f numbers, you're in fact stopping down the aperture ie decreasing the size of the aperture hole =)

Most lenses (especially those non L lenses) have their sharpness peak at about f/8 - f/11

[mismis]

Usually, after f11, you are compromising sharpness for depth of field

[alternatve]

Why on earth would you want to shoot anything after f/11 knowing the perils of diffraction?

A way to combat this is to get a wider macro lens or a FF camera which is less prone to diffraction as a APS-C type.

Samuel

[mismis]

Alot of people shoot after f11. Like I said, if you need th depth and you can compromise sharpness, then stop down

[alternatve]

Originally Posted by mismis Alot of people shoot after f11. Like I said, if you need th depth and you can compromise sharpness, then stop down

I don't know what you mean by alot of people. All my friends don't use f/16 at all on their DSLR platforms and they are much senior then me in this business. It's a poor compromise to have DOF in place of sharpness. If you need the DOF, get a wider lens.

Samuel

[Headshotzx]

Originally Posted by alternatve I don't know what you mean by alot of people. All my friends don't use f/16 at all on their DSLR platforms and they are much senior then me in this business. It's a poor compromise to have DOF in place of sharpness. If you need the DOF, get a wider lens. Samuel

Yes that sure is an alternative

[KY1977]

Originally Posted by alternatve I don't know what you mean by alot of people. All my friends don't use f/16 at all on their DSLR platforms and they are much senior then me in this business. It's a poor compromise to have DOF in place of sharpness. If you need the DOF, get a wider lens. Samuel

You can't do that if you need to take insects from a distance and trrying to maintain a larger DOF.

[antacid]

Originally Posted by alternatve I don't know what you mean by alot of people. All my friends don't use f/16 at all on their DSLR platforms and they are much senior then me in this business. It's a poor compromise to have DOF in place of sharpness. If you need the DOF, get a wider lens. Samuel

maybe "all your friends" don't shoot macro and landscape.

diffraction depends on the pixel pitch of your sensor as well. APS-C cameras probably suffer from diffraction from f/11 onwards, but full-frame cameras can go up to f/16. Besides, I'd rather go for DOF than sharpness. Sharpness is over-rated for me.

[alternatve]

Originally Posted by antacid maybe "all your friends" don't shoot macro and landscape. diffraction depends on the pixel pitch of your sensor as well. APS-C cameras probably suffer from diffraction from f/11 onwards, but full-frame cameras can go up to f/16. Besides, I'd rather go for DOF than sharpness. Sharpness is over-rated for me.

Not quite.

For landscapes I regulary use a wide angle (18mm and beyond) on my APS-C body at f/11 and a wide angle (45-65mm) on my medium format body but now at f/16 or even f/22. That gives me the sharpness plus DOF combination. Considering that a 35mm lens on 35mm film already gives me a DOF of around 1m~infinity on f/11 or close to that, I don't see how much more DOF you need.

Macro wise, I'm afraid I do not have as much experience with it, but I do keep within the "safe" limits of the lens all the time. At high magnification, sharpness is especially important as it shows up very clearly on the picture, less so with a landscape shot.

Samuel

[JohnnyW]

I do own the 100mm Canon Macro lens. I do use it often with extenders and I would say a F/11 or F/16 is a good number to play with for good dof. If dof is really an issue for u on capturing small objects, I suggest u save up and get a TS-E. It will solve most of ur dof problem.

[JohnnyW]

An example from my own picture gallery. Shot at f/16. Nothing very fantastic though on composition etc. Just a newbie shot I take.