After giving up on converting a mint, Canon FD 50L lens (well known camera shop wanted $800 for EOS conversion) which is for sale by the way, I've finally acquired a nice condition, late FL55 1.2 lens and converted it to EOS. The jury is still out on its performance...

The conversion was quite easy. I used a bronze/chrome M42 adapter, which was just wide enough for the rear element to clear. I then drilled 3 very precise holes from the front side, using the removed FL piece as a template. Then from the back side of the adapter, I milled down the stock to the flat plate. The nice thing about this is the bolt pattern is right on the thick ridge of the EF flange and as such the original screw heads need not be countersunk, or the flat plate area weakened by making the screws flush.

I wonder about using the focus stop to achieve infinity. I doubt the front elements are now the same distance to film/sensor as intended, maybe this does matter at all, but in my little brain, I would think the lense would not perform as intended unless the glass that does not move is the same distance to the film plane as orginally designed. If I am wrong, please fill me in, as your method for conversion is much easier than using shims, or sanding/milling/turning. I have a bug up my butt to convert 1 minolta/rokkor each between 24mm and 200mm (well not all, but selected, known performers)

tootalew wrote:
I wonder about using the focus stop to achieve infinity. I doubt the front elements are now the same distance to film/sensor as intended, maybe this does matter at all, but in my little brain, I would think the lense would not perform as intended unless the glass that does not move is the same distance to the film plane as orginally designed. If I am wrong, please fill me in, as your method for conversion is much easier than using shims, or sanding/milling/turning. I have a bug up my butt to convert 1 minolta/rokkor each between 24mm and 200mm (well not all, but selected, known performers)

In these 50mm-ish designs, all the elements move back and forth in the helicoid together, so it doesn't matter. Jim's method should not affect the performance in the least as compared to shimming/sanding, etc.

The potential for the problem you describe exists in lenses that have CRC (floating elements) and/or internal focusing and/or zoom.

This lens, FL 55mm 1.2, does not have a stationary lens, but a lens assembly where all elements moves at the same time. This is the case for the vast majority of lenses, therefore, whatever way you tune infinity focus is OK.

Close Range Focusing as in the Canon new FD 50L, that I have for sale, has a single stationary rear element that does not move, but does change its distance to the other elements as the focus ring is turned, has to have the sensor at the exact register distance and therefore infinity is adjusted by thinning or thickening the adapter, if possible. The high cost of conversion I mentioned above is because the rear element needed to have a housing made for it.

By the way, save for the Minolta 58/1.2, the 2 or 3 Minolta lenses I've looked at all have different mount and aperture arrangements.

Well I have converted 3 so far, the ones im most intersted in converting now are the rokkor-x 50 1.2 and the minolta md 135 2.0 I may take interest in the 24 2.8 the 28 2.0 and the 35 1.8. I took apart the 45 2.0 and because of the cam arrangement for the apeture being on the backside of the mount assembly, you would have to wrap the canon mount around the minolta mount. Not that it could not be done, I have seen it done to a 50 1.4, but at this point in time, I do not have access to a machine shop. I do understand that both of the 50mm (1.4 1.7) are awsome lenses. I just cant get rid of this bug, and want a full line up of Rokkors, even though there are endless options of manual focus lenses. The 100mm 2.5 is now stuck on my 5D and in my opion is one sweet little lens.

Is there anything about the FL Canons which make them easier to convert than the SSC FD lenses and later? I have a very nice SSC 50 F1.4 and a new FD 35 F2, both of which were steller when I shot film. Before I start tearing these apart, does anyone know of any issues with these or later FD's? Seems like I recall reading that the FD mount is more complicated.

Tariq Gibran wrote:
Is there anything about the FL Canons which make them easier to convert than the SSC FD lenses and later? I have a very nice SSC 50 F1.4 and a new FD 35 F2, both of which were steller when I shot film. Before I start tearing these apart, does anyone know of any issues with these or later FD's? Seems like I recall reading that the FD mount is more complicated.

If I recall correctly the difference is the location of the aperture mechanism. In the FL lenses the aperture ring is at the front of the lens (see above shot), where the FD lenses tend to have the aperture mechanism at the rear. Since you need to bring the lens closer to the sensor, modifiying the FD lenses are more difficult since you need to ensure you don't mess with the mechanism.

tootalew wrote:
I wonder about using the focus stop to achieve infinity. I doubt the front elements are now the same distance to film/sensor as intended, maybe this does matter at all, but in my little brain, I would think the lense would not perform as intended unless the glass that does not move is the same distance to the film plane as orginally designed. If I am wrong, please fill me in, as your method for conversion is much easier than using shims, or sanding/milling/turning. I have a bug up my butt to convert 1 minolta/rokkor each between 24mm and 200mm (well not all, but selected, known performers)

The registration distance of Canon FL lenses is 42mm. The registration distance of the SA mount and Canon EF mount is 44mm...So to make an FL lens reach infinity focus on Sigma or Canon EOS DSLR's you simply need to machine 2mm off the lenses mounting boss...This moves the rear element 2mm further back. and you get infinity focus.
Minolta MD mount lenses like Rokkors have a registration distance of 43.5mm, so you only need to machine 0.5mm off the lenses mounting boss to get infinity focus.
However there can be difficulties in acheiving this because most rokkors have rear mounted iris mechansim's which can get in the way of the procedure, and the helicoid stop sliders also get in the way.
The beauty of the FL 55mm f1.2 is that its iris mechansism is front mounted and therefore the rear of the lens is very much neater and easier to convert.

Field testing the FL 55mm 1.2 on a XSi, I thought of a difficult shoot where I could use the thin depth of field. How about isolating the grid of a catcher's mask, foreground/ background glove and baseball against in-focus eyes. Becasue of chromic aberations @ 1.2, this shot was f/1.4.

Mine does'nt seem to suffer from CA WO. Stopped down a bit its every bit as sharp as my Carl Zeiss 85/1.4 planar T*.

My one:

100% (I think) crop of WO/1.2 shot: I'm refering to the pink fringing or ghosting off the fingers. Gone at f/1.4. Lightroom export to jpeg.

That is either coma or movement blur, not CA.

I'm curious, what did you use to make the shim between the adapter and the A/M select ring?

I took a Canon EF rear lens cap and milled/cut down to the right thickness, as it was the perfect diameter. Nice?

Oh great idea. Thanks.

JimBuchanan wrote:
I took a Canon EF rear lens cap and milled/cut down to the right thickness, as it was the perfect diameter. Nice?


That's exsactly what i did in my conversion. I burned a small knife on a gas cooker flame and cut the "flange" part of the cap and sand it a bit. It's perfectly fit. My fire alarm went off at the mid-night thoug

Just put in an order for more rear EF lens caps...

I must say I am enlightened to the fast lens vs slower. I always thought the slower lens design was better resolution @ wide open, but this FL55 is challenging that notion. It really is like having 2 lenses in one. I've been comparing this FL55 to my late Summicron-R and from f/2 smaller its hard to tell the difference in resolution, near or far. In fact, at f/4 to f/8 the FL55 seems sharper in some infinity scenes.

I may have to lock that A--M switch to manual stop down mode.

I have to wonder, is the de facto standard alternative Minolta 58 1.2 really better (especially wide open @ close distances) at the current 2X-3X price difference? Anyone tested both?

I have both of the lenses, FL and Rokkor. Didnt have a chance for a proper test but from the results taken from both lenses, the Rokkor is obviously much much far better than the FL55, IMHO.
Sorry to say but I found nothing amazing from this FL55 but it's still a keeper.

It my be sample variation for my converted lenses but my FL 55/1.2 is sharper wide open the my Rokkor 50/1.2 and I did do a careful test, but the Rokkor is still a keeper.

Tim

manowar wrote:
I have both of the lenses, FL and Rokkor. Didnt have a chance for a proper test but from the results taken from both lenses, the Rokkor is obviously much much far better than the FL55, IMHO.
Sorry to say but I found nothing amazing from this FL55 but it's still a keeper.

tmessenger wrote:
It my be sample variation for my converted lenses but my FL 55/1.2 is sharper wide open the my Rokkor 50/1.2 and I did do a careful test, but the Rokkor is still a keeper.

Tim




I thought we were talking about the Rokkor 58/1.2.

BTW, Tim, I'd like to see how you converted the Rokkor 50/1.2 and some sample shots.

Is there any difference between FL 58/1.2 and FL 55/1.2?

Silentlight wrote:
Is there any difference between FL 58/1.2 and FL 55/1.2?

Yes, the 58mm is an older lens and it was replaced by the 55mm.
The 58mm has a more complex iris mechansim making it more difficult to convert than the later 55mm.

An addendum to this thread shows a refinement of my method of Canon FL 55 1.2 lens conversion. As I was hired to convert another lens, I took the opportunity to turn down the helicoid assembly as described by Alf Beharie. The benefit of this is not only better precision, but eliminating the need of a spacer between the lens and m42-EOS adapter, and not having to mess with the helicoid mechanism at all.

Shown, is the rear of the helicoid assembly and M42-EOS adapter, after 2mm was removed. The infinity focus stop is also seen with the 3 slot screws, and was ultimately used to fine tune infinity.

I've been saying it for a couple years now - those unpainted reflective adapters can cause problems with bright scenes, wide open apertures, and with wide angles.