Olympus Zuiko 20mm f3.5 macro lens

[cws1745]

Apologies in advance if this topic elsewhwere - but I,ve had a good search with no luck!

I have one of these lenses - bought new many years back but never unboxed or used.
Now finally ready to start some macro work in earnest - got the adaptors to fit to my Canon FD bellows.

My questions are - is it a good performer? I have nothing to compare so won't know if it is my inexperience or whatever. What magnification can I expect when using a Canon 1.6 crop sensor with the FD Bellows? Is a lens I could put in front of a prime like an objective?

Any information / explanations most appreciated.

Charles

[ray_parkhurst]

From your questions I assume you have not seen Alan Wood's page on these lenses. Take a look here:

http://www.alanwood.net/photography/oly ... 20-35.html

I think it will answer some of your questions.

[ray_parkhurst]

My questions are - is it a good performer? I have nothing to compare so won't know if it is my inexperience or whatever.
...
Is a lens I could put in front of a prime like an objective?

I don't think Alan's page will address the above, so I'll give some input...

I have the 35mm version of this lens, and it is a good performer, not much different from the Canon version. I also have the Canon 20mm, which is excellent. Both can be beat on APS-C with good microscope objectives, but not by a lot, depending on your criteria.

You could try stacking the lens in front of a prime or zoom but my suspicion is the performance won't improve much at best, and might degrade vs normal mounting. The biggest benefit to stacking happens at lower magnifications. The 20mm is designed for 4-12x, so the potential benefits may not be worth the trouble.

[cws1745]

Good Afternoon and thanks very much for the information - very useful.

If my understanding is correct I could actually aim for 12x magnification if I could extend far enough with the bellows / extension tubes? I'd be very happy if I could achieve that!
My FD bellows only extend by ~135mm so I'd need to use extension tubes to get near the distance from the table in the link you sent.
Am I right in thinking it wouldn't matter whether I put these extensions at the lens end or the camera end (or both)?
Thanks again

Charles

[ray_parkhurst]

If my understanding is correct I could actually aim for 12x magnification if I could extend far enough with the bellows / extension tubes? I'd be very happy if I could achieve that!
My FD bellows only extend by ~135mm so I'd need to use extension tubes to get near the distance from the table in the link you sent.
Am I right in thinking it wouldn't matter whether I put these extensions at the lens end or the camera end (or both)?

Yes, you could certainly get 12x from the lens. Keep in mind that it is an f3.5 lens, so the effective aperture at 12x will be f46. This is equivalent to NA 0.13. This means that when you zoom in to the image, it will be blurry. Depth of field will also be very shallow, ~25um. But if you only view at reduced size, it should look OK. For instance, if you're using an 18MP APS-C Canon (like a T2i...T5i), the full size image is 5184x3456. If you zoom all the way in, there will be very little detail. But if you downsize by 4x (to 1296x864), the image should look quite good.

For extension, I like to use the cone shaped RMS-M42 adapters. They allow you go get closer to the lens with lighting than you can if the lens is attached directly to the bellows. You'll also need a EOS-M42 adapter to mount to bellows. Together they will give you an extra ~55mm of extension. Keep in mind the total extension also includes the distance from the end of the bellows to the sensor, ~44 mm for Canon cameras. But if you prefer to just add extension between the bellows and camera, it will work fine as well. Makes little difference which end you mount to.

Note if you do get a cone adapter, it's best to flock the inside to eliminate reflections.

[enricosavazzi]

The first (of two) generation of this lens in manual aperture format is very sensitive to flare by off-axis illumination. I was forced ro use a 10 mm wide, 8 mm long.lens shade attached at the front. The second generation, also with manual aperture, may be a little better. There is a third generation with automatic aperture f/2 that I know nothing about.