Interesting post on Yahoo Canon FD Users group

Michael · Jan 18, 2010

Having been a long time user of Canon FD (film) equipment I still maintain an interest in what is going on in that sphere. Last night I read this interesting post from Jodie (Yahoo Canon FD Users group) that I think many m4/3 users would also like to consider...

"Using FD lenses on FourThirds does not double the focal length! Since the
FourThirds sensor is smaller, the angle of view is reduced:

AOV = 2 * arctan (D / (2 * F)

where D is film / sensor dimension, and F is the focal length.

While it is true that using converter to mound FD lenses on a microFourThirds will not diminish the image quality of the lens it does not mean the lens will perform well on microFourThirds. The experience of people I have talked with who have used FD lenses on microFourThirds matches my experience using Olympus OM lenses on FourThirds. Wide open the results are disappointing, with low contrast and center sharpness, very low edge sharpness.
Stopped down 2 or three stops things improve considerably, but aren't any better than the Olympus digital lenses, at least not any better than lenses like the 14-54mm f2.8-3.5 zoom. Add to that not having autofocus and having to manually stop down the aperture and I have simply given up on the notion of using vintage manual focus lenses on FourThirds."

Regards,
Jodie "

While this may be the case for many average legacy lenses, some of the results I have seen with L series FD lenses, some Nikon primes and Leica R lenses have been simply stunning and exhibit all the fine qualities that they did with film. There is a lot more to be learned here...

Amin Sabet · Jan 18, 2010

Those are interesting points, Michael.

The first is absolutely right - the focal length of a lens is a physical property of the lens and doesn't change if you mount the lens on a 35mm frame camera, a 4/3 camera, or a Christmas tree :smile:. Likewise, the physical aperture size does not vary, and therefore the f-number (ratio of focal length to physical aperture) also does not vary with the mount.

With regards to legacy lens performance on Micro four Thirds, there are a couple factors at play. The first is that digital sensors don't perform as well with light coming in at an angle as they do with light coming in straight on. This is in contrast to film, which handles both well. This seems to be less of a problem with SLR lenses mounted via adapter, but it is a real problem with rangefinder and C-mount or cine lenses, especially those wider than 25mm or so, where blurry edge performance is very common.

The second issue... *deleted*

mabelsound · Jan 18, 2010

Amin, that "test" is completely bogus--you're uprezzing a crop, of course it's going to be soft! The smaller photosites on an m4/3 sensor may indeed have an impact on resolution, but not anything like that.

Amin Sabet · Jan 18, 2010

Mabelsound, it wasn't meant to be a test. Only an illustration, and the false assumptions were clearly mentioned.

I think it'll be more misleading than helpful to a lot of folks, because it is unlikely to be interpreted in the intended fashion, so I'm going to delete it. Thanks for helping me realize it's limitations.

However, the point I was making is largely unrelated to pixel size. Let me try again in another post...

mabelsound · Jan 18, 2010

I got where you were coming from, but yes, I think it was definitely open to misinterpretation!

Amin Sabet · Jan 18, 2010

Let's take the pixel size issue out of the equation - imagine that you had a film or sensor with unlimited resolution.

Now, let's say that a given lens projects an undesired color fringe 0.01mm in width as measured on the sensor, whether that be a 4/3 sensor or a 35mm frame of film.

Now, take that frame, and make an 8 x 10" print out of it. Which print is going to have the thickest undesired fringe? The print made from the 4/3 sensor will, because it will have been upscaled to a greater degree for the reproduction. Ie, the color fringe occupies a greater proportion of the total image size.

Does that make sense? For a given lens, smaller sensors represent a greater challenge, tending to magnify flaws such as softness and color fringing.

mabelsound · Jan 18, 2010

That does make sense--but, by the same token, it could be said to magnify certain aspects of lens character, like distinctive veiling flare/glow or distinctive bokeh patterns.

Amin Sabet · Jan 18, 2010

Yes, those things can vary in different ways.

mabelsound · Jan 18, 2010

I guess, in the end, I think of m4/3 as a great platform for recontextualizing old optics, which just happens to also have some great autofocus lenses available for it...your milage may vary, but that's what's fun and interesting about it...

Amin Sabet · Jan 18, 2010

No doubt, that is a big part of what makes :43: fun and interesting. I love seeing how all sorts of lenses render on these bodies. I'm hoping out adapted lens image thread gets another jump start soon!

BillN · Jan 20, 2010

deleted - somehow i posted it twice - see following thread

BillN · Jan 20, 2010

Amin said:
No doubt, that is a big part of what makes :43: fun and interesting. I love seeing how all sorts of lenses render on these bodies. I'm hoping out adapted lens image thread gets another jump start soon!

my view also - the older lenses have a different character(s), (brand by brand, size by size, spec by spec), and you can see and explore these with the M4/3.

new (digital), lenses plus clever camera computerisation = one image

Older lenses, when all optical corrections were left to the lens designer, when used on a digital sensor = another, (different?), image

Maybe all (most) digital lenses, (within reason) will perform in the same (a more similar), way when mated to their digital masters

Older glass may not be controlled in the same way and there will be such a wide range of "digital" images to explore using "older" glass which must be interesting to any photographer

after all "what is best"

also i would feel that MF "macro" lenses will perform well and be very "cost effective" when used on an M4/3

My experience to date has been when using MF Nikkors with my D300 - G1 just arrived, and it's a very dull day, plus waiting for an adapter

hodad66 · Jan 27, 2010

Well, I rarely pixel peep so you can't take my word to the
test bench BUT..... since I have gotten my G1 I have
purchased many a Canon FD lens and I'm quite happy.

In fact I gave my "stock" lenses to my GF and shoot mostly
manual or with the 20mm 1.7.