Macro-very narrow focus area at full magnification

Hi,
I bought a Pentax 100mm f2.8 1:1 magnification lens.
If I'm taking a photo of something at the max magnification (very close up to the subject) there's a very small area that's sharp/in focus no matter what aperture setting I'm using. (no examples on hand at the moment)

Is there anything I can do to prevent this or is that just the way it was at max magnification?

Cheers,
pa.

---

Cheers,
Pa
http://www.photoblog.ie where every post have a musical reference as it's title.

That's the first post I've ever seen complaining that a macro image is too sharp and/or in focus

Pa is referring to the limited deepth of field and this will be more and more limited the closer we get.

If you want as much in focus as possible, use the smallest aperture that's reasonable (start with f16 perhaps) and use a tripod as the shutter speed may well be quite slow.

What you are seeing is a law of optics, and that isn't going to change!

---

Best regards, John

Thanks, that's what I thought- 'law of optis'.
I'll post up some photos from my first few weeks with the macro lens soon.

---

Cheers,
Pa
http://www.photoblog.ie where every post have a musical reference as it's title.

Hi Patrick - this is the hard lesson to learn with these macros - a nightmare when a bug sits on a flower that is mowing in a slight breeze - it will slide through your focal layer and it is so hard to catch it the right moment. As John said - without tripod it is often so difficult to find the right layer. BTW - did you make the same observation that autofocus is nearly worthless in max. magnification (I more and more only do a rough manual focus and then do the final focus by moving the camera slightly towards the object or away from it....

---

_____________________________________________

Colors are the lack of darkness

You find more of my pictures here: http://www.pentaxphotogallery.com/artists/axelluther or on my web page: www.axel-luther.com

Another thing to bear in mind when using full 1:1 magnification is that at the point of focus there is effectively 1/3rd in front and 2/3rds behind (thereabouts) actually within the depth of field for a given aperture and therefore in focus. So if you are taking a side on shot of say a caterpillar and you focus on the 'skin' then you lose 1/3rd of the available depth of field which will be in front of the subject. This cannot be overcome with autofocus and therefore you need to train your eye (it's not easy) to focus manually 1/3rd into the caterpillar so as to get as much in focus as possible by utilising fully the depth of field and the smallest usable aperture.
Hope that makes sense and helps.

Search this Forum, or Google, for 'focus stacking'. Might be the answer to your 'problem'.

Focus stacking is one way, but I prefer to work with the limited DOF and try to compose the image to benefit from it. Easier said than done.

Example; if you are photographing something long like a Grasshopper, shoot it side-on if you want most of it sharp. However, shoot it from the front three-quarter view or head-on if you want dramatic impact and do your best to get the critical point of focus on the eye.

Axel gives good advice above; don't try to focus critically by using the focus ring on the lens - move the camera backwards and forwards smoothly and slowly until focus is achieved.

Finally, have you tried the 'Catch in Focus' feature? With a manual lens this is brilliant and can help get your macro shots in focus, but it's no guarantee of success.

Regards
David

---

My Website http://imagesbydavidstorm.foliopic.com

PPG Link
Some cameras, some lenses, some bits 'n' bobs

Anyone know why my post (above) is showing with a sage green background when I view the thread, when others showed with normal grey background?

I think it means that your post is considered to be good information.

Take care.

---

Chris R.

I. El. (Eng). (Rtd).

I think you will find that close up it's nearer...
50% in front 50% behind

---

Pentax K-5 and some other stuff

Algi

Really?, Hmmm thanks Algi - must experiment more !

Fill in the numbers http://www.dofmaster.com/dofjs.html

100mm, 30cm subject distance
f/8 2mm DOF (-1 / +1)
f/16 4mm DOF (-2 / +2)

---

Pentax K10D + Vivitar 55/2.8 macro + Super Takumar 55/1.8 + SuperMultiCoated Takumar 85/1.8 + SuperMultiCoated Takumar 135/3.5 + SuperMultiCoated Takumar 200/4 + Super Takumar 300/4
Pentax K100D + DA18-55ALII + DA55-300
Pentax K5 + FA31Ltd + M50/1.7 + DFA100WR + M120/2.8 (+ DA18-55WR at occasion)

I like that dofmaster....very useful. Shows exactly how little dof there is on macro shots.

---

This space deliberately left blank.