FD 85/1.2 SSC Asph. to EOS Guide
/forum/topic/787723/2

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Alf Beharie
Registered: Apr 18, 2007
Total Posts: 834
Country: United Kingdom

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.




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

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



cogitech
Registered: Apr 20, 2005
Total Posts: 11365
Country: Canada

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.



cogitech
Registered: Apr 20, 2005
Total Posts: 11365
Country: Canada

zombii wrote:
About 31 inches.




m-a-x
Registered: Apr 27, 2009
Total Posts: 406
Country: Germany

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.



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

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.



m-a-x
Registered: Apr 27, 2009
Total Posts: 406
Country: Germany

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.



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

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



cogitech
Registered: Apr 20, 2005
Total Posts: 11365
Country: Canada

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.



Alf Beharie
Registered: Apr 18, 2007
Total Posts: 834
Country: United Kingdom

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.



m-a-x
Registered: Apr 27, 2009
Total Posts: 406
Country: Germany

DaFrunk, I agree to what cogitech wrote. Spring not required.

Alf, the SSC is similarly difficult, not more. In fact, I found attaching such a custom part to the aperture ring easier, since the ring is stronger.



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

The point of the spring:
It is continuly pulling the lever (name it Lever1 for clarity) on real aperture in one direction. So the lever (Lever2) you have to install on the aperture ring need to have accuracy only on the front edge, because it is the only mating surface.
Without the spring, two edges of Lever2 must mate accurately with Lever1 (i.e., two mating surfaces), and throughout the focusing movement of the lens. This could be difficult without adequate tools and rigid materials (me included), especially if Lever2 must be a female one.
With the spring in place, no matter Lever1 is male or female, you only need a narrow Lever2 with its front edge (the one facing Lever1) accurately shaped.

After messing with 17, 50L(still in progress), 85L, 135, 300L with nFD mount, and 55 Asp, 300 Fluorite (and a 24Asp is coming) with SSC breech lock mount, I think the breech lock versions are just slightly more difficult to work with. And it is only because I have to cut across the thick breech ring and sand off its internal threads to provide a cover behind the aperture ring! If there is another way to provide the cover then...

To accommodate the differences in EOS and FD flange distance:
1. nFD:
The total optical distance (OD) of the attachment on the rear must be 3mm.
All I need to do is to trim down the nFD mount ring to about about 1.5~1.6mm OD. The OD of ring is 3mm orignially, but there is some 0.5mm protrusion at the outer edge on the front surface that presses against the aperture ring (to provide a nice feel of click for aperture changes). So you must only work on the rear surface. Then simply attached the M42-EOS adapter (1.5mm or less OD). Follow up with the built-in infinity adjustment of the lens.


2. Breech lock SSC:
The total OD of the attachment must be 2.5mm
Trimming the existing light baffle OD from 1.5mm to 1mm, fabricate a cover behind the aperture ring and install the M42-EOS adapter. Adjust for the infinity.

If you need to reduce the optical length further to make a M42 compatible lens, then you have to disassemble more to trim down the rear mounting surface for the SSC, while for the nFD you just ditch the nFD mount ring completely.

The aperture linkage that is needed to be done is quite similar in nature (though varies from lens to lens.)

Well, may be the twin balls of the SSC's aperture ring can be a hell to install right at the same time .

And, the 300mm F2.8L is more difficult to convert than the 300mm F2.8 Fluorite! Because in the L, the aperture assembly utimately is resting on the nFD's central baffle tube that is removed during the conversion. So you have to cut out the baffle tube and re-install it somehow. OTOH the aperture assembly of the Fluorite is a pretty ordinary one, just a very long ~ long lever is what is required to do the trick.



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

So if I understand what you wrote, using the spring can be helpful for 85 SSC or 24 SSC ASP. Is it compatible with the cogitech's method?



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

Dear DaFrunk,

The spring is not needed if you follow Cogitech's method completely.
Note that in the example (55 f1.2 SSC) in your link, the author installed a spring, so that he could use the original lever on the aperture ring (that means no need to make/install a new lever!) Another example is the 55 f1.2 Asp SSC. I have one and did similarly. I simply drilled one single hole for the spring attachment and no other work for the aperture linkage.

This is another conversion example for the 55 f1.2 SSC. In this example, the author didn't use a spring, so he made a new lever (by combining the original lever with the new part.) Now judge for yourselves which way is easier .

I think it would be fair to say, for some cases, one may find it easier to attach a spring and use existing lever (or make a simple one) than to make and install a new lever with more precision requirement. Now, of course, it is not always possible to install a spring! Anchoring points for the spring do not always pre-exist. And there may be simply no room for the spring, or the spring will get in the way when the lens tries to focus to infinity.

So most of the time you just have to make a precise lever and be done with it. And it is likely to be the case with the 85 f1.2 (SSC or L). I haven't received the 24Asp yet .



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

That's clear now! Welcome to the growing club of 24 asp new owners! I think I'll start modding the 24 asp before the 85 ssc, as it has no rear element so it may be easier (I hope). By the way, in order to mod them I currently have a C/Y adapter (the same cogitech used but with an AF Confirm), a Leica, and a M42 one. The inner hole is large for C/Y & even more for Leica, while it is smaller for M42. Should I order another C/Y right now or can I go with Leica/M42 adapters?



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

Well I only have messed with the 85L and not the SSC, so I cannot say for you. But the 85L surely need a bigger hole than the one in the M42 adapter because the end of the Lever1 would hit the adapter. So I had to enlarged it partially (only the front but not the rear.)

I used the M42 adapter because I wanted to adjust the placement of the rear element. I glued the rear element to the back of a M42-M39 adapter ring, and screwed it inside the M42-EOS adapter. By carefully adjustment (by screwing in or out ) I hoped to get infinity without shaving my 1Ds II mirror.

But now after the fact, if I need to redo again, I may just use a good quality C/Y to EOS adapter. I would just try to adjust the rear element placement by adding different layers of double-side tape (the total protrusion will be 1.2~1.3 mm out of the end of bayonet tabs anyway). After finding the perfect position, just glue everything in place with epoxy.

OTOH, it is easiler to get good quality M42 adapter (most made in brass, a few aluminium) than C/Y adapter (varies quite a lot.) And the M42 adapter has a larger surface to firmly attach the PCB board for electronic focus confirmation.

P.S. I hope the 24Asp will have sufficient edge quality for full frame. I know that, image quality wise, the 24 F2 is better, the f2.8 may be its equal or even slightly better, but the bokeh of the 24A is looking good And I did get a great price for it .



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

Thanks for such precious info. isn't is hard to be sure to glue the rear element so that it is perfectly parallel to the lenses?


"adding different layers of double-side tape" --> where do you put it? on the circumference of the rear element or on the plane face of the mount? I'm asking because if I read cogitech's method he concludes that the solution would be to reduce the thickness of the "internal shroud", while you're talking about "increase thickness". In your configuration, do you remove this internal shroud?



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

Dear DaFrunk,

Are you aware that the flange distance of FD is 42mm while that of EOS is 44mm. On the top of this, the rear element is about 5.5mm behind the FD flange! That means the rear element should be 7.5mm behind the EOS flange. Now take out your C/Y or M42 adapter and measure its total thickness and the height of the bayonet tabs, it should be very clear when the rear element should be. See the related FD85L conversion for additional details (note : 85 Asp is identical in optical arrangement.)

In short, the rear element is attached to the back of the EOS mount. So to those of us without precision tools, we just cut out the metal plate (which holds the rear element) and glue it to the back of EOS adapter. If an even pressure is applied when the epoxy is curing, then the plate should remainly true (or very close, anyway) to parallel. It shouldn't matter if some small pieces double-side tape is added to increase the separation between the metal plate and the EOS mount (like at 3~6 points around the rear of the mount), as long as an even pressure is applied when the epoxy cures.

My FD85 f1.2 is the L (nFD) version, so it is different, but I still use the internal baffle to cut off stray light and dust. And when I converted my 55Asp I reused the internal baffle because
1. it reduce dust/stray light entry.
2. It has a 1mm flange, which is required to attain infinity for FD SSC-EOS conversion. Someone chose to trim the breech lock ring to use it for this purpose and also as a cover between the aperture and EOS mount (as in this example again).



m-a-x
Registered: Apr 27, 2009
Total Posts: 406
Country: Germany

I disagree in one point: M42 adapters work for both the 85/1.2 L and the SSC as long as the M42 thread goes through the entire adapter. In other words, it must be such a M42 adapter without a rear flange.

If the inner lever is not modified, the space inside the M42 thread will be sufficient for the rear of the moving lens group AND the lever.



m-a-x
Registered: Apr 27, 2009
Total Posts: 406
Country: Germany

Maybe I should add pictures. Please excuse cross-posting (from thread: FD 85L f/1.2: a real gem)

M42 mount on a 85 L lens.
Note the very thin rear element holder.
Advantage: no contact between holder and mirror box of camera (5D).
Disadvantage: another custom made part.






And here is the lever:







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