Acanthus - Spot the Difference

Here are three shots of an acanthus flower (part of the 'every type of flower in the garden' project). First is with the Sigma 105mm macro (film era) wide open (f2., second and third are Pentax F50mm f1.7 plus 20mm tube at f2.8 and wide open (f1.7) respectively. All are about 0.5 magnification and same viewpoint but necessarily different working distances and thus perspective for the Sigma and Pentax.

There are subtle differences between the two at f2.8 but which do you prefer and why? And does having f1.7 available with tubes add something useful?

1. Sigma 105mm, f2.8



2. F50mm + tube, f2.8



3. F50mm + tube, f1.7



Steve

I prefer the 105 Sigma image, it has more inherent sharpness, as is usually the case when comparing a true macro lens with a standard portrait lens on tubes. The Pentax 50mm F1.7's are very good though for macro photography when on tubes, I took one of my best ever macros with this combination.

Regards
David

Did you try any with the lenses stopped down for comparison? The Pentax Standard 50mm at 1.7 isn't ever going to look really sharp at full aperture used as a macro lens. At f2.8 it would match the Sigma and provide a truer comparison

A macro lens especially at it's design magnification will easily beat a prime lens at any aperture especially when used for macro.

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The first of the F1.7 pictures is at f2.8 so that's the comparison.

Yes, I systematically stopped down with each lens. Results at f8 are below.

Perhaps worth noting that I tried to focus (manually) on the 'snake's tongue' fork and there might have been very slight subject movement (air is rarely completely still). My main interested was the out of focus areas in real world photography, sharpness would have been easier and more accurately compared using a flat, indoor target.

Sigma 105mm, f8



F50mm + tube, f8



Steve

Sorry, I missed that the first Pentax one was at f2.8. With those the Sigma looks to be better right through. I wonder how one of Pentax's macro lenses would compare?

If someone would send me one on indefinite loan in the next few days ...

I would have tried my Irix 150mm macro, but the Sigma 105mm was already at the limit of what I could do without a step ladder. Some things are just not worth the effort!

Steve

I think for me the sigma are the best as well. Its a pity one can't put the images side by side on screen for compariosn. On another note, it would be good to some images sometime from the Irix 150mm!

Have you tried opening the same thread in more than one tab in your web browser and scrolling to a different picture in each tab? You can then flip between pictures by changing tab. It works for me in Firefox. Not quite the same as putting images side by side, but it's surprising how good the eye/brain is at noticing small differences when you flick from one picture to another and they're at the same place on the screen.

On the other matter, Irix 150mm comparison coming to this thread soon...

Steve

And here is a set including the Irix 150mm macro. Sorry about picture overload, but had to use a more easily reached flower so new pictures with the Sigma 105mm and F50mm + tube needed. f2.8 series first then f8.

Do they make anyone change their mind?

Irix 150mm, f2.8



Sigma 105mm, f2.8



F50mm + tube, f2.8



Irix 150mm, f8



Sigma 105mm, f8



F50mm + tube, f8



Steve