I have been toying with the idea to use a 150-500mm Sigma as a macro by using an extension tube. Before buying a set I used a 2x-tele converter without the lens (tube only). I am amazed and puzzled by the results. All the pictures were hand held. The long lens seem to me a option with insects that are camera shy. I tripod will of course made higher f-stops possible
1. at 500mm I could focus (manual) from about 1-meter to about three meters (this is more than the minimum focus distance with lens only). 1/320 f13 ISO-400 500(150-500)
2. At 150 mm however, I had at most 20cm focus distance I could therefore only use macro 1/320 f13 ISO-400 170(150-500)
Sat 18-Aug-12 09:52 AM | edited Sat 18-Aug-12 09:53 AM by glxman
Nice capture Aart, Nothing wrong with a tele lens, I think the best economical option is extension tubes allowing you to focus at closer distances, I do think the best option is a macro but prime lenses do work well with tubes, I don't know if the tubes work with a zoom though?
jtmcg, (John), is the expert here Regards, Gary
I used to have a photographic memory but never got it developed
The shorter the focal length, the greater the effect of extension. Therefore, at the short end of your zoom, the extension you used would produce more magnification than at the longer end of your zoom. A 50mm lens needs only 50mm of extension (built-in plus added) to get to 1:1 magnification. A 200mm lens needs 200mm of extension.
Thanks to all, "The shorter the focal length, the greater the effect..." Make sense. The zoom works more like a "focus" device. At say 2-meter from the subject one can use the the "zoom" for focusing without changing the magnification. If one zoom out too much, one can not focus. To summarize, if you zoom in to maximum you can change the size by moving the camera. If you zoom out to maximum you can only focus very close to the subject getting about the same magnification as with the maximum zoom. 1/640 f10 500(150-500) with 50mm (2") extension tube
Sun 19-Aug-12 02:50 PM | edited Sun 19-Aug-12 03:25 PM by aolander
"The zoom works more like a "focus" device. At say 2-meter from the subject one can use the the "zoom" for focusing without changing the magnification. If one zoom out too much, one can not focus. To summarize, if you zoom in to maximum you can change the size by moving the camera. If you zoom out to maximum you can only focus very close to the subject getting about the same magnification as with the maximum zoom. "
Kind of, but not really, if I'm understanding you correctly.
Magnification is really only about focusing closer with any lens. Adding extension allows closer focusing hence more magnification. With extension on your zoom, you can focus closer and get more magnification at the short end versus the long end.
Actually, diopter (close-up) lenses are easier to use with zooms, as the subject stays in focus as you zoom in or out and only the magnification changes. Not sure what the filter thread size is on your zoom, but Canon's 500D diopter lens comes in several thread sizes.
I grok what he's saying - in practice that's pretty much the case.
I have to say that I was stunned at how sharp these are given a 2x TC - but then I realized that the optics were removed, so in fact this isn't being shot with a TC. These are, in effect, shot with an extension tube that has oddball EXIF modifiers (I like it!)
The 150-500 HSM OS uses 86mm filters, which are much larger than any known two-element closeup lens.
_____ Brian... a bicoastal Nikonian and Team Member
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Hello Alan, I am also surprised with the result. Referring to the picture on my previous post, I used f7.1, resulting in a small DOF. I noticed that when I changed the zoom, there was no noticeable change in the magnification but the focus field changed. When I zoomed out until every thing was out of focus, the focus-ring reacted but could not bring the picture in focus. When I zoom out to 150mm, I could not focus on the specific object at all. On the coming weekend I will table the results at 150mm, 300mm and 500mm with the same extension tube.
The will be a "range" of distance on which you can focus depending upon the focal length. At the short end the range will be much closer than at the long end, and the magnification will vary depending upon that (distance and focal length). There may be some discrepancy because many lens change focal length (shorten) as you focus closer.