Olympus 21mm f3.5 on full frame digital

My first SLR was an OM1 and so my early years in 35mm photography were shaped by the compact systems that Olympus once made.

The subject of this blog post is the Olympus 21mm f3.5 lens. At 21mm it is a very desirable focal length for landscape wides, architecture interiors and indeed quite a number of photographic uses. Both it and the 21mm f2 are still famed for their sharpness within that focal length.

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But the 21mm is not just a great tool for making images, its a great tool to use. Smooth to operate and light on the camera it feels as nice to use as the images you can make with it.

Pictured here beside my EOS 24mm f2.8 it is snug enough to slip into a pocket. The EOS lens operates nicely in AF mode, but if you want to operate manually that focus ring is just dreadful.

When it came to digital I was perhaps on of the early adopters. Digital cameras such as the Coolpix and IXUS cameras gave me better versatility and snapshots than any of the compact 35mm cameras could produce. At the time I never really thought I'd replace my 35mm camera with one of these digital things. Not because of any "better or worse" concepts, but simply because they did different things.

For me full frame digital has been one of the destinations of digital cameras since the first DSLR was introduced. For one reason of another I've never made the "commitment" and bought a full frame camera. The steep price tag however has always kept me at bay. So as a result I have never been able to answer an important question.

Is full frame worth the commitment?

I happen to like wide angle lenses, and as it happens shallow depth of field is something I like to take advantage of to make my subjects stand out from the background.

This image of the tree on the sand dune was taken with 35mm film and a 24mm lens at f2.8

I know from experience that had I used an APS DSLR for this image (such as my 20D) then the background would not be as distinct from the subject and everything would be more or less in focus.

So while I've had wide lenses such as my Tokina 12-24mm lens on my EOS 10 and 20D cameras there was always something missing for me.

Since getting my 21mm Oly I have not had a chance to use it on a full frame camera such as the Canon 5D. So this weekend I got to borrow a 5D from a mate (thanks Al) to allow me to think this through more and to also give me the opportunity to do some image testing on the Olympus 21mm f3.5, something which it seems there is not much of on the internet.

I took a few images in the back yard getting a feel for the lens and found that it was staggeringly soft in the corners. I only took one image at f3.5 and so I wanted to do something a little more through for a blog entry. So today we had fine weather (and I had some time) so I took my tripod off to the park and took some shots. So, lets look at the overviews of the two scenes I took today (at about midday) with the 21 on the 5D.

All images were taken with manual exposure, using exposure determined by my Gossen lightmeter. Naturally as I stepped aperture I also stepped shutter to compensate.

Image 1
In this image I focused on the building in the background. Below is a contact sheet made from the exposures starting with f3.5 on the LHS and moving to f16 on the RHS.

its pretty clear that at f3.5 there is some significant vignetting.


Image 2
where I tried to focus carefully on that middle green tree. Clearly with a 21mm lens once you focus on anything more than 3 meters from you its more or less the same as infinity.

The contact sheet.

The vignetting is (of course) strongest at the corners, but even at the middle edge of the frame its enough to be annoying at less than f5.6


Vignetting
As I mentioned above the vignetting at f3.5 was significant, so from Image 2 I've taken the left hand edge to show this. Not only is the image significantly darker but colour and contrast suffers somewhat too. Click on this image to load a 100% screen grab.


Sharpness
The middle of the image is unaffected, these are some from the center of image 1


so even at f3.5 if your subject is in the middle (as in my dune tree above) then it may not be a strong problem for you.

Corners predictably fall off badly, this is the lower left corner ...

and this is the upper right corner.



Click on this image and have a careful look at not only the sky density but also the definition of the building (well not that its not clear even at this size).

All of which leaves me feeling a little out to sea. I know from previous testing of this exact lens on 35mm film (both neg and slide) that I didn't see such stark and obvious vignetting or sharpness fall off. For example on this blog post where checked out this lens (using film) against the 9-18mm zoom on my 4/3 sensor digital camera. And again here.

So for those of you who may have been interested in obtaining one of these lenses (the Olympus 21mm f3.5) for use on full frame digital I can say it does an excellent job at f5.6 and smaller aperture, but just be prepared for some softness at f3.5 ... with foreground detail it can be quite a strong effect too. Click this image for a larger version to see what I mean (look in the branches of the tree in the right foreground).



This is the image which started me off checking the lens in more detail. If you look at the grass in the lower left of the image above, that's essentially in the out of focus foreground. So, if you like that look, then great, but you should be aware of if before you go get one.

conclusions?

Well now I feel stuck. This now has me thinking that for ultra wide lenses I'm actually going to be better served in staying with 4/3 (or in my case micro 4/3) while my previous experience with the larger full frame (on film) had me feeling that this lens gives better shallow renderings and being able to work at f3.5 higher effective shutter speeds (at a given ISO) than the Olympus f4~5.6 which is designed for 4/3 (and which is my other contender as a wide lens for my digital setup)

Right now I'm feeling more shakey about buying a Canon 5D than I have ever been.

The lens on film makes great images ...






its just that I don't normally use 35mm film much these days.

Perhaps I should?