Damn the macro ratios

ChromaticAberration · Joined: 23 Dec 2010 Posts: 819 Location: Portugal

So I bought myself a popular lens that supposedly offers a (near) 1:2 macro ratio.

When I look through the view finder with the lens at it's maximum extension (minimum focal distance) I am able to capture about 80mm of a ruler keeping it in focus. According to this (interesting) article, I should divide that for the width of my APS-C sensor, which is about 22mm.

Funny thing is, since 80 divided by 22 gives me 3.6 we are talking about an almost 1:4 ratio, so why in the hell do people call this lens a "macro capable lens"?

Right now I am feeling disappointed since I was looking to get a macro lens and avoid carrying macro tubes, not another 50mm which I don't need anyway.

Do you guys have any good way of telling magnification ratios despite the sensor size? Care to explain?

Thanks in advance.

poilu · Expire: 2019-08-29

you math are right
a 1:2 should view 72mm on FF and 44mm on Aps
if you get about 80mm I can see only 2 answer
or the lens is indeed 1:4
or your dslr is FF and you don't know it Very Happy

DConvert · Joined: 12 Jun 2010 Posts: 921 Location: Essex UK

The magnification ratio of a lens is unchanged by the sensor size, so I too confirm your maths is right.

You don't mention which lens it is, but there seem to be three possibilities to me:
a. The lens is possibly one of those sold with a matched adapter - this is usually the case with 1:2 macro lenses which need the adapter to get to 1:1 (My Cosina is one of these but I've not got the adapter for it) I've not heard of these for lower magnificaton lenses.

b. The lens you got it not the one your reports are about. (Carefully check the markings on the lens)

c. The reports you got your information from are wrong.

Not much help I'm afraid.

Orio · Expire: 2012-12-04

Why not just go out with that lens and take photographs? Rolling Eyes

exaklaus · Expire: 2011-12-02

Blinx123 · Joined: 18 Jul 2011 Posts: 75

ChromaticAberration · Joined: 23 Dec 2010 Posts: 819 Location: Portugal

I bought the lens with a specific purpose in mind and I have no interest whatsoever in using it if it will not be up to my needs. I rather sell it because I am not a lens collector.

As a matter of fact I actually took it with me on summer vacations and was by far the one I used the most.

I am talking about an Industar 61 L/Z MC, since I managed to ruin the preset (it wasn't in good shape to begin with) now I also have to deal with a VERY badly scratched rear element where the coating is almost all gone. The seller only mentioned "cleaning marks on rear element" though. It's a mess!

On top of not making the 1:2 ratio I found the lens to be soft wide open @ 2.8 and I am comparing it to the 135mm preset Pentacon which is not suposed to be the sharpest to begin with. I gotta make some more tests though.

Thanks for the inputs.