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03/14/2007 03:26:43 PM · #1 |
What do i need to buy to convert a 18-50mm f2.8 to get macro function. And can the converter be used with a 70-300mm lens?
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03/14/2007 03:33:33 PM · #2 |
Hmmmm... good question. I have a set of Hoya macro attachments (a +1, +2 and a +4) for a 50mm lens that do a very, very good job. You might want to look into that to see if there are macro attachments that fit your specific lenses. A key is that they must have the correct size to thread onto onto your lens.
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03/14/2007 03:33:40 PM · #3 |
You mean an extension tube?
For a lens to focus close the elements need to move further away from the imaging plane, infinity focus is the closest it gets to the film plane. Extension tubes are just hollow tubes that go between the body and lens, moving the lens elements further away than normal, and in effect making it focus closer.
A dedicated macro lens is just a lens that has a lot of travel, ie. it can move a lot further away from the imaging plane than a regular lens. Macro lenses are also usually high quality optically.
The extension tubes should work with any lens (they contain no optics), as long as you buy the correct ones. You will need to ask a Pentax user for recommendations. The 70-300 will however need more tubes due to the longer focal length. |
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03/14/2007 03:44:42 PM · #4 |
As you can see, there are two options...
1.) Extension tubes
2.) A "diopter" filter
The advantage of option 1 is that there is no additional optical element, so no further degradation of the image. There is light loss (because the image is spread out over greater area).
the advantage of option 2 is that there is no light loss, but if you consider this path, it's better to use a two-element (achromatic) diopter than a single-element one. The difference will be significant; the achromat will have far less chromatic aberration. |
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03/14/2007 03:48:49 PM · #5 |
You could also try reverse mounting the 18-50 on the 70-300, that's how I do my macros.
Shameless plug... |
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03/14/2007 04:12:11 PM · #6 |
Originally posted by kirbic:
As you can see, there are two options...
1.) Extension tubes
2.) A "diopter" filter
The advantage of option 1 is that there is no additional optical element, so no further degradation of the image. There is light loss (because the image is spread out over greater area).
the advantage of option 2 is that there is no light loss, but if you consider this path, it's better to use a two-element (achromatic) diopter than a single-element one. The difference will be significant; the achromat will have far less chromatic aberration. |
Would this be a suitable candidate? hoya filter
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03/14/2007 04:16:01 PM · #7 |
Originally posted by Raziel:
You mean an extension tube? ...
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In my case I use single element 'diopters' as kibic descibes them, not extension tubes. The closeup crocus images and all the bokeh images in this gallery were all taken with one or more of the macro attachment so you can see its pluses and minuses:
//www.pbase.com/azleader/oregonflora
In the past I've used reversed lenses for macro shots and though that works OK it has very little flexibility. ;)
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03/14/2007 04:24:00 PM · #8 |
Originally posted by dmadden:
Would this be a suitable candidate? hoya filter |
Looks to me very much like the set I have except mine is for a different thread size. I use them on KIRBIC's old Canon 10D with the Canon EF 50mm f/1.8 II normal lens. Examples of what you get from them are in the gallery I indicated above.
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03/14/2007 04:50:49 PM · #9 |
Originally posted by Raziel:
The extension tubes should work with any lens (they contain no optics), as long as you buy the correct ones. You will need to ask a Pentax user for recommendations. The 70-300 will however need more tubes due to the longer focal length. |
They will mount to any lens, but their macro effectiveness will be limited by the focal length of the lens in question. They are most effective with middle focal lengths. With long focal lengths, you will need more extension to get the same magnification as you would with a shorter lens. With a wide angle lens, the problem is that you can lose the ability of the lens to focus. (Actually, the lens will focus, but even with the lens set to infinity, the focal point will be actually inside the lens. Interesting, but not very useful.) |
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03/14/2007 04:52:17 PM · #10 |
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03/14/2007 05:35:57 PM · #11 |
This conversion is very interesting but from reviewing all the response and that tutorial in particular, it seems like it could be a very frustrating task. Fixing the aperature wide open limits my ability to control DOF.
Think I'll jus save for a macro lense. Thanks All
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03/14/2007 05:40:48 PM · #12 |
Originally posted by dmadden:
This conversion is very interesting but from reviewing all the response and that tutorial in particular, it seems like it could be a very frustrating task. Fixing the aperature wide open limits my ability to control DOF.
Think I'll jus save for a macro lense. Thanks All |
FWIW, the aperture in the normally-mounted lens is still available to control DoF. Still, reverse-mounting a lens is appropriate for high-
magnification, but of limited use if you want less than 1:1. |
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03/14/2007 05:51:22 PM · #13 |
I have a set of Tiffen diopters that are probably more than 30 years old, and they work quite well. I used them in one of my current challenge photos, actually.
The only difference is that mine are 1/2/3, not 1/2/4. |
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03/14/2007 05:53:49 PM · #14 |
Originally posted by kirbic:
Originally posted by dmadden:
This conversion is very interesting but from reviewing all the response and that tutorial in particular, it seems like it could be a very frustrating task. Fixing the aperature wide open limits my ability to control DOF.
Think I'll jus save for a macro lense. Thanks All |
FWIW, the aperture in the normally-mounted lens is still available to control DoF. Still, reverse-mounting a lens is appropriate for high-
magnification, but of limited use if you want less than 1:1. |
When doing reverse mountings your DOF is usually razor-thin anyway, so aperture changes don't really matter all that much. (No, seriously. It can be difficult to get the entire head of a needle in focus at once.)
ETA: Ok, I was being a little dramatic. Really really small apertures can help with DOF (by making it larger), but your 'normal' apertures are going to have tiny DOF.
Message edited by author 2007-03-14 22:13:23. |
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03/14/2007 06:11:49 PM · #15 |
you can also reverse mount the lens, but it requires an expensive adapter. It should give you 1:1 - 3:1 magnification iirc.
edit: reverse mounted directly onto the camera that is.
Message edited by author 2007-03-14 18:12:16. |
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