# Canon 100 mm USM (not the L)



## davholla (May 25, 2020)

I know that this has a focus limiter but I cannot find information about it on line - what does it divide into and does it make focus work better.

Has anyone tried this and the L lens and found any difference in focusing?


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## compur (May 25, 2020)

instructions:
http://gdlp01.c-wss.com/gds/7/0300003507/02/ef100f28macrousm-im2-eng.pdf


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## Overread (May 25, 2020)

The limiter switch removes a portion of the focusing range for the lens. Macro lenses tend to have very refined focusing for closer distances (small movements on the focus wheel move the focus in small distances); whilst their focusing on the normal distances for shooting at generally a bit less fine (small shifts move the focus a lot). 

The limiter will cut off one half of the focusing segment. So if the lens is already focused into the macro ranges, it cuts out the long distance stuff. If you're in the long distance, it will cut out the macro range.


Basically because macro and regular are so far apart focus wise, chances are you'll only be working on one at a time for the most part. Using the switch means that the focus has far less range that you're not using to work through. When using AF this makes the AF much faster because if it misses focus and starts to hunt, its not hunting through a huge range that you're not using at all. 


Note many use manual focusing for macro because of the gentle back/forward motions that the body has when shooting, become much more pronounced in macro and that combined with less light make it a lot harder for cameras to focus. Some newer camera bodies and lenses have improved on this dramatically, but by and large manual focusing still works generally the best for macro.


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## Derrel (May 25, 2020)

Had the EF 100mm f/2.8 IF macro for several years. The limiter is useful. OVERREAD'S explanation is very good. I have not tried the L macro with stabilization.


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## Derrel (May 25, 2020)

100mm Canon EF-IF macro, Canon 5D. Speedotron flash, small 24"x24" MIC softbox. 180k web reduction.


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## Original katomi (May 25, 2020)

I have the l series and have just used it for this weeks challenge DOF
using with an extension tube U had to turn  off the limiter and have the full range
This is the resulting image


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## Derrel (May 26, 2020)




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## Derrel (May 26, 2020)

Not really the best limiter distance choices....usually we see something like 10 feet to MFD, or 1 meter to infinity.But this is a 1:1 capable macro lens, and we do not want it to have difficulty in finding a target and go racking itself into 10-inch distance.

In this case, the limiter is designed to make the lens better as a field telephoto or portrait lens. The focus limiter locks out really close focus distances, and prevents the lens from going into the "macro" ranges. This lens is not a fast focuser, even though it has a USM system. It also has an 8-bladed diaphragm, and gives somewhat neutral-to-rough bokeh and sharp-sided bokeh balls when used against back-lighted foliage or light sources.  It is not a " pretty imager", like  say the 135 mmm f/2 Canon L, or any number of newer lens designs. I think the Tamron 90 AF-SP has prettier bokeh.

If you read Ken Rockwell's review, he just fawns over this lens. I have no idea why he describes the focusing as being instant...not my experience.  I often found it to be slow. I had it with the 20D and the 5D. I was not overly fond of it. The new Sigma 105mm that Ron Lane recently got is IMHO a much "prettier" imager.


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