What is the mag. difference between Sigma 180mm 1:2 and 1:1 Macros?

What is the difference between half a dollar and 1 dollar?

One lens has the maximum ability of making half size pictures (1/2 of the original dimensions), while the other one takes life size (1:1) pictures.

So, what is your real question, since you knew all of that?

I checked my old Sigma f5.6 180mm macro, It says 1:2 at 0.55m and 1:2.5 at 0.68m.

It New Sigma f3.5 180mm macro says, 1:1 at 0.46m

Where is 1:2

Where is 1:2?

We don't know: ask Sigma. Or get out a ruler and figure it out for yourself.

If two macros with the same focal length have greatly different magnification ratios at the same distance it's because they change (shorten) their focal length as they focus closer. The 180mmm is only at infinity.

I am not at all familiar with the technical details of the Sigma lenses, but a lens that can go to 1:1 means it can focus close enough to produce a live size image on the film (or CCD/CMOS) without the need of any extrnsion tubes or close-up diopters. A lens that can "only" go to 1:2 means its minimum focus distance is not as short/close.

Keep in mind that macros frequently need critical manual focusing. While we mostly shoot at f11, 16, 22 or perhaps even slower to gain depth of field, a wide maximum aperture will really help focusing. IMO an f5.6 lens will give you a pretty dark viewfinder; whether that is a problem or not is an individual decision.

Where is 1:2?

If you can get 1:1 on a macro lens, you can get 1:2, 1:3, 1:5 etc for free by not extending the lens by as much as to get 1:1. In math terms: 1 = 1:1 > 1:2=0.5 > 1:3=0.333 etc .

If you want something exactly pictured on film in a 1:2 reduction (half life size), simply take a ruler (metric) and make sure you see exactly 72mm horizontally in your viewfinder (assuming 100% shows for the 36 mm wide film)

Good luck, and there must be a macro tutorial soemwhere on the web. My Sigma 1:2 capable macro actually displays the reduction ratios on the barrel. Do you have these lenses? Have you looked?

Thanks everybody for your answers,

Well, my real question was: (and i'm sorry that i really haven't been precise in that matter) How can you have two 180mm Macro lenses with almost the same minimum focusing distance and same angle of view, but with different degree of magnification? (in this case 1:2 and 1:1)

And Mark Ciccarello answered this question to my satisfaction: Quote "If two macros with the same focal length have greatly different magnification ratios at the same distance it's because they change (shorten) their focal length as they focus closer. The 180mmm is only at infinity"

I dont have the 180mm f3.5 Sigma Macro, but am considering getting one instead of the old f5.6.

Thanks! Per

Essentially this is done by racking the entire lens away from the film plane (most often) and can be done internally so it doesn't seem like it's happening. 1:1 is done by having the distance from the nodal point to the film plane being twice the focal length of the lens. So your 100mm lens is now 200mm away from the film plane (more or less). In the process of moving from infinity (image distance and focal length are same) to 1:1 you will pass through 1:2, 1:3 and so on. Often these are marked on the lens.

By moving the lens further away, you can easily do the math to see that the focal length has changed (shortened).

Hi Carl,

I know that if i have a 1:1 lens, that it will pass through 1:2, 1:3 and so on, but my question was at what distances are these magnifications on the new sigma 180 f3.5 macro lens. The only thing Sigma tells me is where 1:1 is, and that is at 0.46 meters. I dont have the new lens, so i cant read the markings where 1:2 or 1:3 is at.

I am trying to find out, if i gain more distance to the object im photographing if i buy the new 1:1 180mm instead of the old 1:2 180mm.

From what i can read from your answers i will not gain anything at infinity, but the closer i get to the object the more distance i will gain using the new f3.5 180mm Sigma.

Lets say im taking a photo at 0.55 meters with my old f5.6 180mm, this is a 1:2 magnification.

How much further away can i stand with the new f3.5 180mm taking the same 1:2 image??? 0.70 meters?

Cheers Per

there's some math you can do to calculate that, and if nobody has told you yet, you can e-mail me and if I get a chance to I'll let you know. I doubt it will be as much distance as you'd like however. Remember though that you can always put on a diopter, or use extension tubes to get you farther away but magnify the subject more.