Which one is sharper

Hi
I am currently shooting macro with Pentax 50mm M 1.7 + extension tubes, and I am rather happy with the sharpness. I am often using f1.7 - f2.0.

I am however considering purchase of a proper macro lens and these two are on my list:
- tamron 90mm 2.8 macro
- sigma 50mm 2.8 macro

Firstly, are these to 1:1 macro? Secondly, how do these two compare in terms of sharpness (wide open) with Pentax 50mm M 1.7?

thank you

These are totally different beasts. Macro lenses, usually 1:1 these days, offer flatter field and better close up performance. The price we pay is a smaller maximum aperture and a less compact body. If you're often using f/1.7 - f/2 then you can't do that with a macro lens.

What do you want a macro lens for, as that will dictate the best lens for the job.

The Tamron 90mm f2.8 is indeed a 1:1macro

As to sharpness I find the limiting factor is my shaky hands

The 1st is the Tamron @f2.8




The 2nd is my manual 50mm @1.7 plus 58mm extension tubes



In both cases I focussed as close as I could get with the focus on the thin line above the thick one labelled '1'. Both are at about 45 degrees and hand held

regards
Bernard

What do you mean by 'flatter field' John?

This is a great comparison Bernard. To be honest I would be happy with both images in terms of sharpness.

Small detail of food is what I need a macro lens for. I am now thinking if 90mm is not too long focal length. Would sigma 50mm be more comfortable to work with capturing wider view when needed but also capable of closeups?

A lens will naturally project an image that mimics the shape of the elements in terms of where sharpness falls - in other words, the plane of sharp focus is curved. This means the centre could be sharp but the edges out of focus, and vice-versa.

Fast lenses tend to suffer more from "field curvature" so a 50mm f/1.4 is less suitable than an f/1.7 for close ups of flat subjects.

A macro lens is corrected to give a flat field, which makes it suitable for images of flat subjects such as documents. They will remain sharp corner to corner.

If you are not intending to use the lens for insects and other moving objects then a longer length macro is not really required (although they can also be a very good portrait lens).

It may even be worth looking at a Pentax DA 35mm f2.8 macro which will also serve you well as a walkabout lens.

For pictures of food, why not try the humble close-up lens first? Stopped down to f/11 or f/16 it should give excellent results.

In terms of focal length a 50mm Macro, if needed, might be better. Normally I would opt for a 100mm Macro but sometimes that does leave us too far away. Why not a Pentax macro lens? Even a second hand manual focus one could be ideal for what you intend it for.

John, any examples of old manual pentax macro lenses capable of 1:1?
I mentioned Tamron and Sigma as these are cheaper than Pentax ones.

Most manual focus ones go to 1:2, but the addition of an extension tube will take them to 1:1 with no problem.

1:1 is extremely close - it seems very close for food?

I do look for such extremity Although 1:2 + tubes would be ok if significantly cheaper. Do you know any such old and sharp lenses from top of your head?

K100/f4 k50/f4
m 100/f4 m50/f4
will do the job nicely

Geordie01 has it in a nutshell.

With Adapter K even a screw thread SMC or Super Takumar 50mm f/4 would do very nicely.

I briefly looked at these now... we obviously have a different understanding of "cheap" These are comfortably over £100 from what I can see. Am I right or was I looking in the wrong places?

Tamron and Sigma won't be cheap either, no macro lens is.

How about the idea of close up lenses or maybe extension tubes? That will be less expensive.