MWDs of Sigma 150mm macro lens

[peterbolson]

At present I use a Tamron 90mm macro which is pretty sharp & fine for insects that keep still when you approach them, but it is external focussing so that the barrel extends alot, especially at 1:1 magnification. Thus at 1:1 the Minimal focussing distance ( from front of lens to subject ) is only 9cm, at 1:2 it is 19cm & at 1:3 it is 29cm.
I wondered what the comparable MWDs were for the Sigma & whether people thought the extra few inches gained makes a significant difference to what they could photograph. Thanks.

[Lancashire Lad]

Hi Peter,

I posted details of lens to subject distances for various Sigma macro lenses in post No.13 on this thread: -

Good macro lens for Pentax K10D

If the info there doesn't give you what you need, all the details are on Sigma's website.

Regards
Mike.

[Markulous]

I use the Sigma 105mm and 150mm and can't say there's much difference in either distance or extending vs internal barrel when it comes to getting 'up close and personal'. I like the 105 for fast MF and the 150 for it's tripod ring for fast landscape/portrait switch (I mainly use a monopod or tripod). Oh, and it's 15in vs 12in for those two lenses (that's subject to sensor distance)

[pressld2]

Just measured it with my Sigma 150 and it's 19.5cm from subject to the front lens element or 14cm from subject to lens hood.

Dave P.

[Lancashire Lad]

Originally Posted by pressld2

Just measured it with my Sigma 150 and it's 19.5cm from subject to the front lens element or 14cm from subject to lens hood.

Dave P.

I'm led to believe that the figures quoted for minmum focussing distances by Sigma (i.e. 38cm for the 150mm f2.8 macro) are from the subject to the actual film/sensor plane, and not from front of lens to subject, as I previously thought.

There still seems to be an anomaly here, since the 150mm lens is physically 13.7cm in length - so 13.7 plus your 19.5cm = 33.2cm, which would need the camera's sensor to be mounted 4.8cm behind the lens mount.

My 180mm f3.5's minimum focus is 24.6cm from front of lens. (Sigmas minimum focus distance for the lens is quoted as 46cm). The lens is physically 18.2cm in length so 18.2 + 24.6 = 42.8, which would require the sensor to be 3.2cm behind the lens mount.

I assume that the minimum focussing distance could well have slight variations between different examples of any given lens though.

EDIT - For reference, these are Sigma's quoted "Minimum Focus Distances"

Sigma 50mm x f2.8, 1:1 macro lens: - 18.9cm
Sigma 70mm x f2.8, 1:1 macro lens: - 25.0cm
Sigma 105mm x f2.8, 1:1 macro lens: - 31.3cm
Sigma 150mm x f2.8, 1:1 macro lens: - 38.0cm
Sigma 180mm x f3.5, 1:1 macro lens: - 46.0cm

Regards
Mike.

[pressld2]

Originally Posted by Lancashire Lad

I'm led to believe that the figures quoted for minmum focussing distances by Sigma (i.e. 38cm for the 150mm f2.8 macro) are from the subject to the actual film/sensor plane, and not from front of lens to subject, as I previously thought.

This is true, Mike, but unless I'm missing something it's not a particularly useful figure. When you're stalking insects the key measure is how close your front element or lens hood is going to be and whether that's too close. I can't think of any circumstances in which I would want to know the distance from subject to film/sensor plane. And anyway, wouldn't that differ depending on which body you mounted the lens on? Or do all bodies from all manufacturers have the same distance between sensor plane and the lens mount?

Dave P.

[Lancashire Lad]

Originally Posted by pressld2

This is true, Mike, but unless I'm missing something it's not a particularly useful figure. When you're stalking insects the key measure is how close your front element or lens hood is going to be and whether that's too close. I can't think of any circumstances in which I would want to know the distance from subject to film/sensor plane. And anyway, wouldn't that differ depending on which body you mounted the lens on? Or do all bodies from all manufacturers have the same ditsnce between sensor plane and the lens mount?

Dave P.

I'm with you on this Dave. One of the prime considerations when purchasing the 180mm was the quoted minimum focussing distance of 46cm - I fully assumed that this was the distance from front of the lens to the subject. - Not so

The hood on the 180mm reduces the distance by another 8.5cm, such that the actual front of hood to subject distance is only 16.1cm.

Regards different manufacturers sensors, I assume that the different lens mount dimensions on the lens (depending on what manufacturer's camera it is designed for) will take account of camera differences to sensor plane.

Regards
Mike.

[peterbolson]

On one website I read that the MWD for the Sigma 150 at 1:1 magnification was 20 cm. At this MWD my Tamron is only giving me 1:2 magnification, but by moving 11cm nearer I get 1:1. The same article says that at 1:3 the MWD for the Sigma is 45cm compared with 29cm for the Tamron. I'd be interested to know what the Sigma is at 1:2 .
It seems to me that for alot of extra money I'm only going to be able to stay back a few inches to get the same result so is it worth it or would I be better trying to perfect my "creeping up on it" technique.

[peterbolson]

I think that, for me at the moment, the answer is to use a Kenko extension tube with my Tamron. A 36mm tube gives me 1:1 magnification at a MWD of 21mm with the lens set at infinity with the option of better than 1:1 if I extend the lens. I hadn't tried this before because I have always had my SB600 flash set to auto mode & I couldn't adjust the flash output when the extension tube was in place & the camera in manual mode ( I don't understand why ). I have now discovered that I can do this with the flash in manual mode.
Thanks to everyone for their help & advice.

[peterbolson]

Just to correct what I said last time. The flash does in fact work in auto mode with the camera in M mode - I don't know why I had always thought it didn't !