Macro Lenses, I don't understand...

[Ultra Magnus]

What does it mean to have a 1:1 or 1:4 magnification? I mean, I have a 18-200 kit lens w/ my camera, and it has a min focus distance of 1.5'. 200mm, with a 1.5' focus distance and it has a 1:3.7x magnication factor... Then I look at a 180mm macro (close to 200mm), and it also has a 1.5' min focus distance, but it has a 1:1 magnification factor. What gives? Whouldn't 200mm @ 1.5 feet be more "zoomed in"?

Thanks.
BM

[SmartWombat]

What they quote is the image size compared to the original subject size.
So a 1:1 macro can reproduce an object life size on the film (or digital sensor).
1:3.7x means your image is just over 1/4 the size of the subject.

But your macro lens only achieves that magnification in macro mode.
Put it back to normal focus mode and it should be comparable to the 200mm.

[Ultra Magnus]

But your macro lens only achieves that magnification in macro mode. Put it back to normal focus mode and it should be comparable to the 200mm.

How does that work? Does the magnification mode make it act like a longer zoom? I guess I'm a bit confused...

thanks,
BM

[mwfanelli2]

What they quote is the image size compared to the original subject size.
So a 1:1 macro can reproduce an object life size on the film (or digital sensor).
1:3.7x means your image is just over 1/4 the size of the subject.

But your macro lens only achieves that magnification in macro mode.
Put it back to normal focus mode and it should be comparable to the 200mm.

Also, macro lenses have a flat field that normal lenses do not. This is extremely important if you are taking images of flat objects.

Forget about the magnification bits. Macro 1:1 means that the image is EXACTLY the same size as the object itself. The 1:4 means that the best you can do is having the image 1/4 the size of the object itself.

If you aren't clear what a macro is for, then wait! Macro lenses are only for specialty situations where you actually need them. If you haven't reached that point yet, don't sweat it and save your money
!

[Ultra Magnus]

Also, macro lenses have a flat field that normal lenses do not. This is extremely important if you are taking images of flat objects.

Forget about the magnification bits. Macro 1:1 means that the image is EXACTLY the same size as the object itself. The 1:4 means that the best you can do is having the image 1/4 the size of the object itself.

If you aren't clear what a macro is for, then wait! Macro lenses are only for specialty situations where you actually need them. If you haven't reached that point yet, don't sweat it and save your money
!

I'm well aware of what macro lenses are for, and I understand what a magnification ratio is. I just don't understand how they work. I understand focal length and minimum focus distance. I just don't fully understand how a lens w/ similar focal lengths and min focus distances can have different magnification ratios.

Maybe your the kind of peron that understands what they do, and doesn't care how they do it, but I'm the kind of person that likes to know how things work. Just the nerd side of me coming through, I guess...

BM

[SmartWombat]

Well for a start, the macro lens has to move the lens further from the focal plane to magnify the image.

[Loupey]

Sounds odd indeed.

I've noticed before that some kit lenses have spec's that seem distorted like that. I have a hunch that, in order to push the focusing limits to the ultimate minimum (so that they can put the "macro" designation on these lenses), the actual focal lengths are downshifting towards the wider end at extremely close distances.

Yes, focal length and focusing distance will determine magnification. I bet that if you compare the image of the zoom at 200mm at 1.5' with the image of the 180mm at the same 1.5', you will see a marked difference in the angle of view (i.e. focal length). That is the only explanation for the difference in magnification.


I have a feeling that in order to make some lenses sound more versatile, manufacturers are forcing the limits of the focus/zoom beyond what they would normally be. Nikon does it as does Canon and all 3rd party manufacturers. An example: Canon's 70-200mm f/4L focuses down to 3.9' and has a maximum magnfication of 0.26x yet their own 28-200mm will focus down to 1.5' but still only has a max mag of 0.28x. Somethings definitely up with that.

In summary, I would say that one needs to be very careful in reviewing the technical specifications (zooms in particular) and make no assumptions about its capabilities.

[jgredline]

I have learned not to pay attention to a Macro zoom lens. To me it is just a zoom lens.
I learned this when I got a real macro lens. It was the the Tamron 90mm F/2.8 1.1

I am now eyeing a 50 F/2.8 1.1 MACRO and I already have an FA 50mm F/1.4 non macro. There is a difference..

One thing I have noticed is that my 90mm macro focuses slow compared to my other lenses. Has anyone else noticed if TRUE macro lenses focus slower?

[Ultra Magnus]

ok, so I've been looking around abit and with what I reading here I'm thinking macro lenses have like an "extenstion" tube built in, kind of? Anyway, I did run across an odd contraption, and they have a few on ebay right now though at the time I didn't undestand what they were, but they are called reversing mounts or something similar. Basically, they screw onto the filter threads and you install your lens backwards on your camera, supposed to allow for big mangifications, more than 1:1. Anyone hear of this?

BM

[mjs1973]

ok, so I've been looking around abit and with what I reading here I'm thinking macro lenses have like an "extenstion" tube built in, kind of? Anyway, I did run across an odd contraption, and they have a few on ebay right now though at the time I didn't undestand what they were, but they are called reversing mounts or something similar. Basically, they screw onto the filter threads and you install your lens backwards on your camera, supposed to allow for big mangifications, more than 1:1. Anyone hear of this?

BM

Yes. This is a very common practice for creating a very inexpensive macro lens. I plan on on ordering one later this week when I order some other things from B&H.

Copy Kot just posted a photo taken using one of these reversing rings in the NW forum a week or so ago. He also has included some photos of the set up. Check it out here:

Spider mite & gnat

[freygr]

ok, so I've been looking around abit and with what I reading here I'm thinking macro lenses have like an "extenstion" tube built in, kind of? Anyway, I did run across an odd contraption, and they have a few on ebay right now though at the time I didn't undestand what they were, but they are called reversing mounts or something similar. Basically, they screw onto the filter threads and you install your lens backwards on your camera, supposed to allow for big mangifications, more than 1:1. Anyone hear of this?

BM

NO the focusing helical can just focus closer than a standard lens and the old Macro lenses also were like F 3.5 and were very sharp.