Macro photography question

I'm no expert but I find that when using my DFA100 I invariably have to focus manually. I might use auto focus to get roughly in right place but then go to manual focus to make the final adjustment.

I think there are two reasons for this. Firstly, for most of my macro shots, I am using a tripod and the camera is fixed so often there is not an auto focus point exactly where I want to focus and secondly the depth of field is small for close-up shots and I have to tweak the focus to get the DOF spread where I want it.

I think the DFA100 is a great lens. It is becoming one of my most used lenses and seems to be the lens that wins competitions for me . It has a very sensitive manual focus adjustment and once you are happy with the focus point you can lock it so you don't accidentally shift it when taking the shot.


Glyn

Algi's and Glyns comments cover the main points but it is important to remember the raw visual data from the eye is subject to a massive amount of processing in the visual cortex before being routed to the part of the brain that then makes sense of what we are looking at in the viewfinder and defines what we perceive as the critical point of focus in the field of view. By contrast, the AF sensor and associated algorithms that are used 'in camera' to define 'correct focus' are primitive in the extreme; even in the best currently available cameras. Most of the time, as we all know, this is rarely a cause for concern, but it becomes significant when when approaching 1:1 and greater because the depth of field is frequently less than or equal to a couple of mm; especially when one considers that all current AF systems (tin hat on in anticipation of a barrage of 'corrections') are stepping and not step-less, as I assume remains the case when focusing manually.

Many posts on this forum, and on others, cover the issue of focus calibration and the fact that, even on lenses not intended for macro photography, adjustment is often required to ensure accurate focus (manual and AF) and this may be another factor that you need to consider.

Penultimately, I, and others, have found that eye cup magnifiers, even when the magnification ratio is quite modest: e.g. the Pentax O-ME53, can make accurate manual focusing much less 'hit and miss'. Yet others combine one of these with a compatible, third-part focusing screen (e.g. from the KatzEye range) but, despite my deteriorating eyesight, I have not found this necessary.

Finally (honest!) have you eliminated the possibility that what you perceive as 'out of focus' is in fact blur caused by excessive camera shake/'mirror-slap'?

Hope at least some of this adds to the excellent advice given in the earlier and more succinct posts of others

Jon

IMO there is no such thing as a bad macro lens.

Tamron 90mm, Sigma 105mm, Pentax D-FA 100mm are all very good lenses.

WIth regard to the Sigma vs Pentax question, both very sharp, Sigma is better made imo but Pentax is lighter and more compact.