LoCA is the least of my concern, in fact LoCA is almost certain for massive apertured lenses. The bigger the aperture, the thinner the DoF and hence more abrupt transition between focal plane and blur regions. This is why LoCA is greatly reduced when you stop down.

Unless of course it was made with APO glass, in this case it's not.

I would be more worried about flare though, even with SSC coating I'm getting quite nasty flare when shooting with light source in the frame. Time to look for a hood as well.

Congrats Leon.

I have not noticed flare being a big issue with this lens, but I've always used it with a hood, because I bought one for it before I had even completed the conversion.

This is the one I got. http://cgi.ebay.ca/New-Metal-72mm-Screw-In-Lens-Hood-For-Nikon-HN-20-HN20_W0QQitemZ200358167013

Works perfectly, as it is for an 85mm lens and is 72mm thread. Knowing that metal is protecting the front element is reassuring, too. (I purchased it from that e-bayer, BTW).

Paul,

Thanks for the guide and the link to the hood. I've been meaning to try my hand at converting my 85/1.2 SSC as well.

Thanks a lot Paul. I've just placed an order for the hood with that eebayer, probably will receive it next week.

cogitech wrote:
Leon Noel wrote:
I also took some measurements but without the internal shroud (for the sake of infinity) the rear element may touch the next group.



There should be enough thread room there to turn the rear element out slightly more beyond the mount, which should prevent the elements from touching. Of course, this also increases the risk of mirror issues.


Hello all,

I'm a new challenger for the 85/1.2 SSC modding. Finally, did somebody try to put the internal shroud off? As I own a 5D2, I can imagine using the live view mode in (rare) cases where I need infinity. Furthermore, testing the mirror shaving is easier with this body (when switching off the live view, I already do this with M42 lenses).

Bonus question : do you know anybody having done the 24/1.4 mod? I own this lens, the rear element goes as far as the 85/1.2 rear element we're discussing. The thing is that losing infinity is a much bigger handicap for such lens... Is it worst modding this lens?

Thanks by advance

I never bothered removing the internal shroud (to try to achieve infinity) because I never found myself needing any more distance from the lens. This also resulted in the lens being perfectly compatible with unshaved 5D (II) mirrors.

With the setup I had, it would simply be a matter of: 1) removing the new mount (which includes the rear element in its original, threaded assembly), 2) sliding out the internal shroud (it is not attached in any way), 3) turning the rear element in its threads in order to allow full travel of the focusing group, and 4) replacing the new mount.

If the rear element is left in the wrong position, the second element will collide with it when focused to infinity (due to the removal of the shroud, which has a flange that is normally sandwiched between the new mount and the base of the barrel). If this mod was done, the resulting position of the rear element would require a mirror shave on 5D (II), and likely other FF bodies.

I have since sold the lens. I found a much cheaper alternative and I really needed the money I had sunk into the 85/1.2 SSC.

DaFrunk,
You don't need to remove the internal shroud, you just need to sand down its height . It contributes about 1mm to the optical path, and the built-in infinity adustment cannot accommodate without it.

To get infinity focusing, the rear two elements will need to get to paper-thin separation (<0.1mm) from each other (disclaimer: this is from experience with the FD85L on a 1Ds II). So you must test with great care, and use the infinity limiter as the mean to prevent lens collision. And even so, whether you get infinity without mirror shaving may depend on your particular 5D's mirror arrangement. Every little bit counts here, as the 1Ds series get better alt. lenses compatibility (versus the 5D), (may be) by just a hair or two better mirror clearance.

* The mirror of 5D is glued in place by double side foam. Imagine the tolerance involved, it is not hard to understand why some 5Ds get better mirror clearance. I wonder who will get brave enough to poke his 5D mirror off and stick it back a little bit inwards to get better clearance. But for all the work, it may be even better to shave the mirror jut a little bit more .

** For the 24 Asp, search the forum! JimBuchanan has converted one and reported that it cleared the 5D (YMMV). The mirror is closest to the front when it is swinging near the top. OTOH, the last element protrudes only at the very center. so it handily stays out of the path of the mirror. BTW, m-a-x is converting one, and I have one coming, too .

Thanks a lot for your 2 answers!

Unfortunately because I'm french I'm not sure I understand everything. Let me sum up the situation so that if I'm wrong you can correct me :

- sand down? = reduce its height? I understand infinity can't work without the last rear element. Do you mean the trick is to polish it on sandpaper on a plane surface?
- infinity limiter : what's this? a screw to adjust infinity?

Concerning the 24 asp I'll make a search as you suggest. "it cleared the 5D" --> does it mean "It's OK"? Cool! I'm impatient to read your feddback and JimBuchanan's one about this lens on a digital FF...

DaFrunk wrote:

- sand down? = reduce its height? I understand infinity can't work without the last rear element. Do you mean the trick is to polish it on sandpaper on a plane surface?


No!!! Do not sand the rear element, if that is what you mean.

He means you can reduce the thickness of the flange on the internal shroud (with sand paper), so that it does not add so much thickness between the base of the barrel and the new mount. My suggestion was to remove the internal shroud entirely, but his idea is to simply make its flange thinner. It is a good idea. Please refer to the 4th and 5th photos on page 1 to be sure what the "internal shroud" is. As you can see, the shroud has a flange that is sandwiched between the barrel and the new mount. The flange needs to be thinner.

This is what I meant, indeed

Bonne chance!

Merci!

In fact I share your point of view cogitech, I already own a 85/1.8 EF so infinity is not mandatory, while on the opposite I would appreciate a smaller distance scale. Could you tell me what is your minimum focusing distance?

I'd like to get focus up to 30m, that would be cool.

Dear cogitech,

Thanks for the clarification!

Dear DaFrunk,

Please proceed with great care and a great deal of logical thinking. These are some great pieces of glasses. Aviod breaking/scratching the glass element!

Actually it can attain infinity more easily without the last element, but the image quality suffers a lot at larger aperture.

With the last element in its original "designed" position, it will hit the mirror of full frame EOS camera (and APS camera EOS-10D and older). If you use newer APS camera, you can use this original configuration.

To work with full frame camera, you either:
1. trim down the front of the mirror.
2. move the last element slightly forwards (about 0.5~0.8mm, I cannot measure accurately without risk of scratching the glass). But with this adjustment, the front part of the lens has to move backwards more (towards the last element) to focus to infinity. So, if the mirror is too forward (in some 5Ds), infinity focus cannot be attained because the last element collides with the front part of the lens.

On my 1Ds II, the mirror is less forward (actually it retracts slightly backwards when swing up) so I can attain infinity focus. But it is a close call, because the last element and the second-last element is very close to collision (< 0.1mm).

DaFrunk wrote:
Merci!

In fact I share your point of view cogitech, I already own a 85/1.8 EF so infinity is not mandatory, while on the opposite I would appreciate a smaller distance scale. Could you tell me what is your minimum focusing distance?

I'd like to get focus up to 30m, that would be cool.

I forget the precise min. focus distance of the lens I had, but it was definitely less that the original 1m. Maybe 0.7-0.8m.

About 31 inches.

cogitech wrote:
I am sorry to tell you, it will not work.

The issue is; as you change focus distance, the posts will drop deep inside the barrel and so the aperture will disengage. This is why the post needs to be extended and the fingers need to be recessed as I have done it.

Why did'nt you just bend the legs of the fork down as I did on my FD 85/1.2L?...That way you would'nt have had to extend the "post"/lever.

Indeed, I was wondering the same question after having seen a 24 SSC mod with this option

Alf Beharie wrote:
cogitech wrote:
I am sorry to tell you, it will not work.

The issue is; as you change focus distance, the posts will drop deep inside the barrel and so the aperture will disengage. This is why the post needs to be extended and the fingers need to be recessed as I have done it.

Why did'nt you just bend the legs of the fork down as I did on my FD 85/1.2L?...That way you would'nt have had to extend the "post"/lever.




If you read the thread, you'd see that Leon tried this as well, and I explained to him that it would not work because the mechanisms would then disengage as you focus the lens to closer focus distance. If you only want the aperture to work when focused at infinity, then your idea would work. If you want a fully functioning aperture throughout the focus travel, then the only way to do it is how it is detailed here. Leon soon realized that I am correct, and he did it the right way. If you bent the fork legs down too far, they would prevent the focus from traveling back to infinity again. The FD 85L is irrelevant to the discussion. They are completely different lenses with respect to aperture mechanisms.

zombii wrote:
About 31 inches.

The 85L and the 85 SSC aspherical have different coupling desing, as cogitech says.

FD 85 L: lens side of the coupling is male, aperture ring side should be female (a fork)

FD 85 SSC: lens side of the coupling is female, aperture ring side should be male

I wrote "should be" because who knows what other people invented.
For instance cogitech (no offence meant :o)

In both lenses, my custom-made part is attached to the aperture ring and from there it goes DOWN into the lens and connects to the standard part at the lens side.
In my case it would not work with such an extended post because I used a M42 adapter which is too narrow for the rear of the moving lens group AND such a post.

max, could you show a picture or a schema of your system? As cogitech is saying, "If you bent the fork legs down too far, they would prevent the focus from traveling back to infinity again". Is it the case in your configuration? I will use either a C/Y adapter, or a M42 one.

Hi, I did not make pictures during the 85 SSC conversion process.
However, you can find pictures from the FD 85 L here: http://www.fredmiranda.com/forum/topic/757502/6
and on page 8 of the same thread you can see methods of other users.
The thing I attached to the aperture ring of the 85 L is the female self-made coupling mechanism. In case of my SSC, it is a male part but the direction and depth is comparable.
If you shape it well from any hard metal part, you can fix it with screws to the aperture ring of the SSC, which is more solid than the "L".

It takes some time to find the perfect shape of the male lever for the SSC:
A) If the lever is too long (protrudes too deep) it will prevent infinity.
B) If too short it will slip at close focus distances, and aperture coupling is lost.
C) If too far left, the blades will not open fully.
D) If too far right, the blades will be wide open too soon.
E) If the lever is skew, aperture will change during focusing
But when you got it right, it will give you absolutely perfect aperture control throughout the focus range.

m-a-x, cogitech, can you tell me whether the using of a spring is possible as this guy did on a 55/1.2?

http://forum.mflenses.com/canon-1-2-55mm-s-s-c-eos-conversion-documentation-t24118.html

Possible? Probably.

Necessary? No. I don't even know what the point would be, to be honest. The aperture ring, once rigged properly to the aperture mechanism, is perfectly capable of both opening and closing the blades. I am not sure what functionality the spring would add.

Looking at the pics of the rear of the FD 85mm f1.2 SSC Asp in this thread I have to say it looks a lot more complicated to convert than the L version. The FD 85/1.2 L is difficult enough but the extra difficulty of converting the aperture mechanism of the SSC version would surely put a few people off buying one compared to the L version.
Its certainly put me off anyway.