Aperture/focusing distance changes at different FL for zoom lenses?

Started Mar 21, 2013 | Discussions thread
revio Senior Member • Posts: 1,731
Re: Aperture/focusing distance changes at different FL for zoom lenses?

So I went out to test a number of M4/3 zoom lenses today and was majorly disappointed by 2 things as I zoomed to higher focal lengths:

Many seemed to rapidly close down the aperture, and some had very long minimum focusing distances.

Of course I expect these things to change, but was surprised at how quickly they did so. For example with the Olympus 14-42 kit zoom it seemed that just by zooming slightly the aperture was suddenly at 5.6, and I couldn't focus at closer than about 90cm (my estimates, not measured precisely...). These are absolute dealbreakers for me.

1. Is there any chart/guide which shows at what focal lengths a lens closes down to smaller maximum apertures?

2. Comparing lenses on this site side-by-side, the "minimum focusing distance" seems to be that at the widest end. Is there any chart/guide to show the minimum focusing distance at different focal lengths?

I found, after writing my first comment, I wanted to try my lenses out for these parameters. Of course I had quickly went beyond the "comment editing time limit". Thus, here comes my observations of my 4 available zoom lenses:

All, except one, have linear "aperture darkening" as I zoom upwards. The one exception was the Zuiko 14-54mm/2,8-3,5 which maintained a full F:2,8 from 14mm up to and including 18mm.

My Micro Zuiko Digital 12-50/3,5-6,3 was, on the other hand, the one exception to the norm among the 4 lenses I tried in that it did have variable minimum focusing distance. All the other lenses had exactly the same minmum focusing distance kept at all f-lenghts, allowing a difference of a few millimeters.

(Within for example a centimeter, or two, I´d still consider a lens to have, in practise for most uses, a "fixed" minimum focus distance. Maybe I´d be interested to make a more severe test, but I think I´m not very much in need of knowing that. In practise it wouldn´t be of a major importance to me)

My assortment tried today:

Zuiko Digitals: 14-54/2,8-3,5,  40-150/4-5,6,  14-42/3,5-5,6

M-Zuiko Digital 12-50/3,5-6,3

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Aim & Frame

 revio's gear list:revio's gear list
Konica KD-500 Zoom Olympus OM-D E-M5 Olympus E-M1 Olympus Zuiko Digital ED 50mm 1:2.0 Macro Olympus Zuiko Digital ED 14-42mm 1:3.5-5.6 +7 more
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