ZOOM LENS that doesn't change length

Started Dec 23, 2012 | Discussions thread
OP AstrManKen New Member • Posts: 13
Re: ZOOM LENS that doesn't change length

dsjtecserv wrote:

AstrManKen wrote:

iancrowe wrote:

The expensive ones!!!

In the case of Canon the following are IF (internal focusing)

EF 16-35 f/2.8L II USM £1030.00

EF 17-40 f/4L USM £595.56

EF 70-200 f/2.8L USM £959.00

EF 70-200 f/2.8L II IS USM £1754.98

EF 70-200 f/4L USM £473.51

EF 70-200 f/4L IS USM £889.99

(All prices current on Amazon.co.uk)

Sigma used to produce the 100-300 f/4 EX IF DG HSM APO which was internal focusing but I believe it is now out of production. You may be able to pick one up secondhand.

You may find photozone.de a useful reference. All their reviews are accompanied by photographs of the lens in question, usually showing the minimum and maximum extension.


Hi Ian

Thanks a lot for your help.

I'm not worried about dimension change when focusing as the lens will always be focused at infinity or very near infinity. Its the change in dimension while zooming that matters

It looks like the lenses you recommend don't change dimension when zoomed too?

I can vouch for the 17-40 f/4 and 70-200 f/4 IS; neither extends when either zoomed or focused.


Hi Dave

Thanks for all your help. The EF 70-200 lenses look good, but are very large almost 200mm long which is a bit big to get in the instrument.

The 3:1 zoom range is a bit small so I might have to use two different gratings to get the range of resolution in the spectrum or with one grating I'm going to have to compromise and maybe use a lens that does have some extension

Do you have a feel for which lenses have the sharpest imaging, ie very high MTF in the range say 40 - 200mm range.

Its a bit of a balancing act to get a lens that's not too big, doesn't extend at all or not too much, has a focal length about 40-200 and has fantastic imaging and doesn't cost too much.


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