How good is this Sigma?

Impulse buy from eBay, but I'm wondering if I have bought a pig in a poke.
Does anyone have any experience of this lens and if so is it any good and what do you think it should be worth.

Sigma APO MACRO 180mm f2.8

I have the later EX DG model, which is 1:3.5 I think, and AF. Its my favourite macro lens.

What makes you think you have a pig in a poke?

Well, a 180mm f2.8 is never to be sneezed at. I take it the lens is PKA rather than AF?

Makes my 120mm f2.8 look tiny!

I believe (although I'm not 100%) that its not a 1:1 macro like the newer version but 1:2.

Hi Mannesty, I don't think I have a pig in a poke I hope I haven't. The later F3.5 looks like a beauty but they never come up S/H

Dangermouse: you are right it is PKA and as for size it is huge and weighs a ton, the best part of 2kg.

I have had a small play and it seems razor sharp but there is no daylight in the week any more what with work taking up the lightest part of the day. I will have to try to take it out this weekend, weather permitting, to see what it is capable of.

Out of interest it was on eBay for months at a BIN of £299 so I offered the seller £210 and he took it this is why I am a bit wary as to whether it is a good one. I assumed if it was a good one it would have gone weeks before and had I just been the fool who parts with his money. I suppose I just need reassuring that I haven't bought a duffer.

As long as there are no gremlins, I think you've bought yourself a nice macro lens for not very much money.

Apparently it is 1:2 not 1:1 but that's not going to make much difference, is it?

1:1 macro lenses are able to reproduce objects at 1:1 scale as I understand it.

You can easily get 1:1 with an extension tube of the correct length.

I have noticed that some fairly priced items tend to hang around for ages. Everyone is trying to pay less than market value so they tend to ignore the BIN lots.

Is it internal focus or external focus?

The FL of internal focus lenses varies/reduces as you focus closer.
An internal focus 180mm is not really much different than a 100mm
external focus lens for macros.

AF isn't generally used for macro work anyway.

1:1 probably refers to the 35mm frame.

A 1.4x converter is the easiest way to get better than 1:2

1:1 is 1:1. The reproduction on the DSLR APS-C sensor will be "life size" just as it is on the 24x36 film frame. The area covered is a little bit less than 16x24 mm with any 1:1 lens.

OP: I use a Pentax M 100/4 macro lens. It is MF, goes only to 1:2 and is manual exposure to boot. I have a 50mm extension tube that I use on the very rare occasions that I need to work between 1:2 and 1:1. For your lens, you would need a 180mm tube, or keep the working distance and use a 2X tele converter to get to 1:1. You would need to study up to determine which converter would work best with your lens. I use my macro for bugs, so the lens to subject working distance of your 180 would be almost twice that of my 100mm.

That's correct about 1:1. It can be confusing, because if you
were photographing a 36mm long bug on 35mm you would not need
1:1 on the APS-C to fill the frame with it.

Some info on IF lens FL's here link

This suggests that the FL of a 180mm IF lens at 1:1 is 107mm
So the 180mm isn't such a big advantage.

I'm confused now but in answer to the IF question, it is and as I normally use a Pentax A f1.7 50mm on tubes I am mostly right on top of my subjects and most of them get scared off. However I have developed a very stealthy approach as a consequence.
Interesting point about the 2x TC, I have a Kenko with the contacts (but they don't work) but it does give some very good results with a quality fast lens attached.

Sorry Mike, I missed your comment from earlier, you are correct it is 1:2 which is supposed to signify it's not true macro but I've been reading articles about getting longer macro lenses and getting a better working distance and when I saw this I thought all my Christmas's had come at once. But was wary about buying it as it is old then when no-one bought I felt justified in not jumping in at £299. It was on eBay for months when I noticed the make an offer option appear so I offered £210, and he took it. I suppose I am asking for reassurance that I have not spent too much.

Steve, I can't say either way whether it's a good or bad lens as I have never tried one and I doubt many people have tbh. I did briefly have the 3.5mm 1:1 version but sold it as I was getting similar results with the D-FA 100mm f2.8 and Pentax 1.7x teleconverter (plus I bought it for a very low price on Ebay and was made an offer I couldn't refuse).

Basically I think you have just got to use it for a while and decide for yourself if it's worth keeping or not

£210 for a 180mm f/2.8 sounds like a bargain as long as it
will produce good results. It should do because they had a
cheaper f/5.6 version.