Light loss at 1:1 (sig 150mm)

squishy · #1 (**permalink**) 11-08-2010, 10:34 AM

Unboxed my brand new sigma 150mm f/2.8. All in perfect condition as I'd expect.

Mounted it onto my 40D, and went out into the garden to give it a try.

Excellent quality, and a nice working distance as I'd expected, but I seemed to be getting very slow shutter speeds at 1:1.

Shooting in very bright, direct sunlight at f/8.0, I was only getting 1/125sec at ISO 400. I take, the photo and it's correctly exposed. But in the same situation, my old fuji gives me over 1/250 sec at ISO 200 f/8.0, and that is also properly exposed. Also, if I set it up on the tripod, then move the focusing distance to infinity and back, the shutter speed pretty well quadruples at infinity to what it's at at 1:1. I'm aware that this might also be to do with the cameras metering as the subject goes out of focus, but it does it in all metering modes. And this images at both infinity and at 1:1 are properly exposed, even though the ISO and aperture are the same, but the shutter speed is a quarter of what it is at infinity at 1:1.

I was expecting some lightloss at 1:1, but this seems to be losing 1.5-2 stops.

Obviously to get around this I can increase the ISO, but even with the massively better ISO performance than I'm used to, I don't really want to be shooting at ISO 800 or 1600 all the time. Even when I use the tripod (which is most of the time), the slow shutter speeds are still a problem unless there is absolutely no breeze at all.

All in all, this is rather worrying me. I already really like the feel and performance of this lens, but I'm just not sure how I can work around 2 stops less shutter speed.

Can anybody help with this?

Gill Catton · #2 (**permalink**) 11-08-2010, 10:45 AM

Quote:

Originally Posted by squishy

Unboxed my brand new sigma 150mm f/2.8. All in perfect condition as I'd expect.

Mounted it onto my 40D, and went out into the garden to give it a try.

Excellent quality, and a nice working distance as I'd expected, but I seemed to be getting very slow shutter speeds at 1:1.

Shooting in very bright, direct sunlight at f/8.0, I was only getting 1/125sec at ISO 400. I take, the photo and it's correctly exposed. But in the same situation, my old fuji gives me over 1/250 sec at ISO 200 f/8.0, and that is also properly exposed.

I was expecting some lightloss at 1:1, but this seems to be losing 1.5-2 stops.

Obviously to get around this I can increase the ISO, but even with the massively better ISO performance than I'm used to, I don't really want to be shooting at ISO 800 or 1600 all the time. Even when I use the tripod (which is most of the time), the slow shutter speeds are still a problem unless there is absolutely no breeze at all.

All in all, this is rather worrying me. I already really like the feel and performance of this lens, but I'm just not sure how I can work around 2 stops less shutter speed.

Can anybody help with this?

Can't help you at all because I'm rubbish at this stuff, I have a very loose grip on what does what and I tend to just alter things until a picture looks right

but I didn't know you had a 40D when did this happen? Have you always had it? (feeling like I've missed a thread somewhere)

squishy · #3 (**permalink**) 11-08-2010, 10:54 AM

got it yesterday Gill

(thread titled 'camera upgrade recommendations')

Gill Catton · #4 (**permalink**) 11-08-2010, 11:24 AM

Quote:

Originally Posted by squishy

got it yesterday Gill

(thread titled 'camera upgrade recommendations')

Oh Yey!! Congratulations you, I remeber you were hankering after one!

squishy · #5 (**permalink**) 11-08-2010, 11:43 AM

Just something to add:

I've tried the same test in shutter priority mode. If I set it at a shutter speed that gives me f/8.0 when focused at infinity, it opens it up to somewhere around f/4 when I focus to 1:1.

Lancashire Lad · #6 (**permalink**) 11-08-2010, 01:45 PM

Hi squishy, congrats on getting such a fine set up.

I agree with what you say, and have noticed similar effect with my Sigma 180mm. I imagine it's just a function of the light gathering capability over a large area versus that over a small area.

But as I always use a tripod, and am shooting static subjects, even multi-second exposures aren't a problem, and I can keep the ISO at 100 (200 max).

I can't suggest any solution other than the use of suitable flash and diffuser equipment that most insect photographers seem to use on anything other than bright days.

Regards,
Mike.

Jim Ford · #7 (**permalink**) 11-08-2010, 02:14 PM

Save up for a Metz 15 MS-1 'ring' flash - you'll like it!

Jim

squishy · #8 (**permalink**) 11-08-2010, 02:28 PM

I had a look in the user manual, and apparently it is just a normal trait of this lens.

After going out shooting, I don't think it'll be a problem. It's the only small flaw I've found with it!

ISO 1000 on the 40D is still miles better than 400 was on my fuji.

I'll save up and get a flash set up some time, for when using the tripod isn't practical.

Jim: How easy is it to diffuse a ring flash? It's just that the design of them makes it look like using a diffuser would be quite difficult.

rogpow · #9 (**permalink**) 11-08-2010, 03:43 PM

Quote:

Originally Posted by squishy

I had a look in the user manual, and apparently it is just a normal trait of this lens.

It's a normal trait of all macro lenses at 1:1 to lose 2 stops of light, not just the Sigma. Nothing wrong with your lens.

matt_xyz · #10 (**permalink**) 11-08-2010, 04:12 PM

Hi Adam,

This is all quite normal, and isn't specific to this lens. For virtually all of my Sigma 150 shots I use a tripod, a plamp, mirror lock-up and a cable release - it's the only way to get sharp images unless you're shooting in very strong light (which obviously isn't very photogenic) or using flash.

Ring flashes are very difficult to diffuse, I would recommend a regular flashgun which you can heavily diffuse and use on a side bracket.

Matt