25 mm f1.4 or 20 mm f1.7 - my choice and why

Started Sep 5, 2011 | Discussions thread
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Ian Morison
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25 mm f1.4 or 20 mm f1.7 - my choice and why
Sep 5, 2011

Hi Everybody,

the Pan/Leica 25mm f1.4 is now available in the UK and, reading the posts and reviews, I was very taken with the idea of getting it to complement my G2 outfit of a Pan 14-42 (I can't find anything wrong with it despite what some say!) and Pan 45-200 along with two legacy lenses, Zeiss Contax G 45mm and 90mm.

But the 20mm f1.7 is also admired and so I thought that I should do an appraisal of the two before making a purchase. These were my thoughts and conclusion.

Cost: In UK 20 mm around £300, 25 mm around £480. More than 50 percent extra. I could have stretched to that though, so this was not a major factor in my decision.

Size and weight: My G2 system is a holiday camera for use where my Nikon D7000 sytem would be too bulky and heavy. (The carry-on weight allowance on UK airlines is down to 5kg on some flights and I need to carry a netbook as well.) So the small size and weight of the 20mm would be some advantage.

Image quality: Looking in detail at some comparative tests it is not obvious to me that the 25mm is vastly better. At f1.7, the 20mm appears better than the 25mm at 1.4 both centre and edge. At f2, the 25mm is a touch better in the centre but a lot worse at the edge. At f2.8 centres of both identical, but 25mm edge has lept up and exceeds 20mm by some margin. From f4 to f8, the 20mm centre is slightly better, but the edges worse. At f11 and f16, the 20 mm appears better than the 25mm at both centre and edge.

[These comparisons are from the Polish website linked to in the forum in the last few days.]

So the 25mm has an advantage towards the edge in the range f2.8 to f8. That may well be worth having. At f2, f11 and f16, the 20mm appears better.

Bokeh: Out of focus imaging. 20mm is reckoned OK but 25mm is superb - this might be a really good reason for buying the 25mm.

Focal length: This was the clincher for me. In ancient days, I much loved my Hexar 35mm and Leica Minilux 40mm compacts and, with DSLR's, mostly used 35mm as a prime. I found 50mm a touch long.

So, much as I had yearned for the Pan Leica 25mm, I decided to buy the Pan 20mm. From its first day's outing yesterday, when it was the only lens that I took out with me, I have no complaints.

One point though, as mentioned in another post, in "P" or "Ia" mode the G2 tends to use maximum (or close to) aperture with a very high shutter speed. 1/800 of a second is not needed with a 20mm, so its probably best to use in aperture priority mode set at about f4 (where lens is at its best) unless you need a shallow depth of field or light levels are low.

I am sure others of you will have other ideas and maybe, when Father Christmas is feeling generous he might get me a 25mm as well!

Cheers,

Ian Morison

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Ian Morison

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