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05/22/2007 03:45:32 PM · #1 |
I know it might be a stupid question but :)
Why should we use macro lens? Let me extend my question further, suppose I go for 100mm macro lens and I have 70-200mm L series lens and now I am taking picture of same object using both the lenses (70-200 will be set to 100mm when taking picture). Will there be any difference in the photograph?? knowing that Macro is design for macro photography and 70-200mm is a telephoto lens..what else? What extra benefit I have using a macro lens...can some one please throw some light on this topic? A technical aspect would be helpful :)
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05/22/2007 03:49:44 PM · #2 |
The macro lens is:
- Designed to focus much closer*
- Designed to have a very "flat field"
- Has precision focusing
*The 70-200 probably can focus close enough to give 1:4 magnification. That is to say, something about 90mm long will fill the frame. True macro lenses can achieve 1:1 magnification. the image on the sensor is the same size as the object in real life. Something about 22mm long will fill the frame. Big difference.
Message edited by author 2007-05-22 15:52:17. |
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05/22/2007 03:51:03 PM · #3 |
Macro lens can focus at a short distance thus giving you a greater maginification. True macro can do 1:1 mag. which means a 1cm size object will make 1cm image on your film or sensor
70-200 can only focus at 4ft distance and do only 4:1 mag |
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05/22/2007 03:56:31 PM · #4 |
A macro lens is simply a lens that lets you focus closer. But, if you can focus with the object closer to the lens, you get a larger view, and more magnification.
If you take your 70-200 and focus as close as possible, it should have around a .21x ratio (meaning an object 10 mm in length is projected onto the imaging chip as 2.1 mm long. With a macro lens, you'll get 1.0x, meaning something 10 mm will be 10 mm on your imaging chip -- a much closer view.
For example, this image is around 1.0x magnification on a 350D (same imaging chip size as the 20D):
Try seeing how close you can get to a penny, and you'll see the difference. FYI, that was only cropped a tiny bit horizontally, that's essentially a full frame shot.
To experiment on your own, take a lens (50mm f/1.8 is usually pretty good) and take it off your camera, turn it around, and hold it in front of the hole while you look through the viewfinder. That is essentially how I took the image above, although I used a Nikon 50mm f/2 and a reversing ring.
Edit: Whoops, bunch of people fastposted me. Oh well.
Message edited by author 2007-05-22 15:58:15. |
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05/22/2007 03:58:15 PM · #5 |
Will there be difference in the picture when the object is at the same
distance lets say 4 feet? Last night I was in Circuitcity and there I tried above two lenses and I could not figure out the difference in the picture, for me both of them were looking same. I am sure I must be missing someting. |
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05/22/2007 04:12:03 PM · #6 |
Originally posted by pgirish007:
Will there be difference in the picture when the object is at the same
distance lets say 4 feet? Last night I was in Circuitcity and there I tried above two lenses and I could not figure out the difference in the picture, for me both of them were looking same. I am sure I must be missing someting. |
Nope, you're not missing something. When the macro lens is focused further away, it acts like a normal 100mm lens. So there *should* be no difference between the picture from the macro lens and the 70-200, when focused to the same distance. The macro lens will, however, almost certainly be sharper. FWIW, a macro lens makes a great portrait lens. The precision focusing means focus is often somewhat slower, so macro lenses are not usually good sports lenses. |
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05/22/2007 04:33:17 PM · #7 |
Thanks for all the information!!!!
another question though :) do we have best practise to use macro lens? what should be the minimum distance when we are taking pictures? |
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05/22/2007 05:17:33 PM · #8 |
If you look up the lens specifications (like if you're shopping online at B&H or somewhere) then it should tell you what the minimum focusing distance is. I'd have to look up mine to be sure, but for a 100mm macro I'd say it's likely to be around 12 inches?? That's off the top of my head though. It will also tell you the magnification rate. True macros are produced at a ratio of 1:1--meaning that the picture you took is (in essence) the same size as the object you photographed. So that photo of a penny above, would actually be the size of a penny.
So, to answer your original question, each macro lens has a different minimum focusing distance. I generally use manual focus (I think most people do) for macro work. I zoom my lens all the way out and then start moving closer and closer to the object until I have it in focus.
And YES! It does take some practice :-) More than I would like some days! |
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05/22/2007 07:13:41 PM · #9 |
Originally posted by pgirish007:
Thanks for all the information!!!!
another question though :) do we have best practise to use macro lens? what should be the minimum distance when we are taking pictures? |
That's going to depend on what you're shooting and how comfortable you feel working close or far away.
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05/22/2007 07:14:18 PM · #10 |
| Also some traditional style macros, meaning those that focus close using their focusing mounts instead of focal length shortening, will gain a lot of length as it reaches its MFD. Most macros will include a more important spec, its working distance. That is the actual distance from the front element to the plane of focus. |
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05/22/2007 07:41:55 PM · #11 |
I have a macro related question. If I have a 60mm Macro lens that's rated 1:1 mag ratio, and the lens works on both a film camera (full frame) and a 1.5x crop factor, will the magnification be more on the digital. A 10mm object on a smaller sensor will be more of the frame, right?
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05/22/2007 07:52:05 PM · #12 |
Originally posted by TonyT:
I have a macro related question. If I have a 60mm Macro lens that's rated 1:1 mag ratio, and the lens works on both a film camera (full frame) and a 1.5x crop factor, will the magnification be more on the digital. A 10mm object on a smaller sensor will be more of the frame, right? |
The physical magnification is the same. The image o the sensor is still the same size as the object at 1:1... *however* you are absolutely correct that, on the APS-C (cropped) camera a smaller object will fill the frame. It's just like you cropped the center 23.6x15.8mm (for the D200) out of a 36x24mm image. |
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05/22/2007 08:00:49 PM · #13 |
There's a trick you can use to turn any lense into a macro lens. Just detach the lense from your camera and hold it slightly away from the camera.
Of course, there's a problem with light leaking in since there's a space. You can get rid of this light leak by using extention tubes.
That's what I do when I need to focus closer. No need to buy a new lense. |
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05/22/2007 08:19:57 PM · #14 |
Originally posted by Nullix:
There's a trick you can use to turn any lense into a macro lens. Just detach the lense from your camera and hold it slightly away from the camera. |
But it is important to note that you lose auto focus, some EXIF data, and possibly other features. |
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05/22/2007 08:38:40 PM · #15 |
Originally posted by skylercall:
Originally posted by Nullix:
There's a trick you can use to turn any lense into a macro lens. Just detach the lense from your camera and hold it slightly away from the camera. |
But it is important to note that you lose auto focus, some EXIF data, and possibly other features. |
Not necessarily. Depends on the extension tube. If AF is retained, it will not be as reliable, however.
It is always true that you lose infinity focus with extension tube(s). |
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