FD 85/1.2 SSC Asph. to EOS Guide
/forum/topic/787723/1

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pengland
Registered: Aug 21, 2008
Total Posts: 540
Country: Canada

Paul,

My name is Nick....and my FD 85L 1.2 is on the way. I will post pics once I have it and the conversion is complete. I have to carry out the mirror shave on my 5D as well....so lots of work ahead!



cogitech
Registered: Apr 20, 2005
Total Posts: 11322
Country: Canada

Nick,

Keep in mind that the FD 85L conversion is different regarding aperture function, according to Dim.ka.



pengland
Registered: Aug 21, 2008
Total Posts: 540
Country: Canada

cogitech wrote:
Nick,

Keep in mind that the FD 85L conversion is different regarding aperture function, according to Dim.ka.


Paul,

Yes, I realize this. I have already converted four other nFD lenses (50mm f1.4, 50mm f1.2, 100mm f2.8 and 135mm f2). If it is anything like the same arrangement my only "new" hurdle will be the positioning of the rear element and of course the mirror shave. I have tuned all my lenses to infinity up to now and have stayed away from use at infinity with those that have proven to collide even after reducing the rear element holder. I guess it is time to bite the bullet though and gain full functionality. A 2mm reduction should give full functionality to at least 6 of my converted lenses that have restricted use at the moment.



Leon Noel
Registered: Dec 26, 2007
Total Posts: 565
Country: United States

My Dremel arrived today, so naturally I would resume the mod.

Here's the result (sorry pic taken with phone):







Close range test shots, all f1.2































Tomorrow I'll shave 5D mirror and fine tune infinity.



alexandre
Registered: Jun 30, 2005
Total Posts: 2621
Country: Brazil

hmm, quite a bit of LoCA... but for the proce and FL it's very good!



Leon Noel
Registered: Dec 26, 2007
Total Posts: 565
Country: United States

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.



cogitech
Registered: Apr 20, 2005
Total Posts: 11322
Country: Canada

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).



hdan
Registered: Oct 01, 2004
Total Posts: 164
Country: United States

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.



Leon Noel
Registered: Dec 26, 2007
Total Posts: 565
Country: United States

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



DaFrunk
Registered: Jan 22, 2010
Total Posts: 36
Country: Germany

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



cogitech
Registered: Apr 20, 2005
Total Posts: 11322
Country: Canada

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.



kf_tam
Registered: Apr 13, 2009
Total Posts: 71
Country: China

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 .



DaFrunk
Registered: Jan 22, 2010
Total Posts: 36
Country: Germany

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...



cogitech
Registered: Apr 20, 2005
Total Posts: 11322
Country: Canada

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.



DaFrunk
Registered: Jan 22, 2010
Total Posts: 36
Country: Germany

This is what I meant, indeed



cogitech
Registered: Apr 20, 2005
Total Posts: 11322
Country: Canada

Bonne chance!



DaFrunk
Registered: Jan 22, 2010
Total Posts: 36
Country: Germany

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.



kf_tam
Registered: Apr 13, 2009
Total Posts: 71
Country: China

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).



cogitech
Registered: Apr 20, 2005
Total Posts: 11322
Country: Canada

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.



zombii
Registered: Apr 11, 2009
Total Posts: 1062
Country: N/A

About 31 inches.



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