FD 85L f/1.2: a real gem

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Archive 2009 · FD 85L f/1.2: a real gem

kf_tam
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p.8 #1 · FD 85L f/1.2: a real gem

Hi Ron,

Mine protrudes only about 6.9mm, and the two rear elements separates only less than 0.1mm at infinity (but more than 0.05mm). I placed a 3M tape (0.05mm) and a 3M Post-it sticky paper (0.1mm) alternatively between the elements to test the minimum separation when I was setting the infinity limit.

Best Regards,
Edward Tam

ronchappel wrote:
Hi Alf
Is yours an FD85/1.2L version? If so then yes, the concave side needs to face backwards.
It must protrude 7.4mm* further back than the mount surface of the lens.
At infinity the two rear elements are about 0.5-1mm from touching .sorry-cant rem the exact amount

If its less than 7.4mm you won't be able to achieve infinity and the elements will touch while trying.

If it's more than that it's not such a problem -just don't let the mirror hit it unnecessarily

*This info i got elsewhere.Mine was closer to 7.5mm
My experiments in moving the rear element showed that having this exactly right is not critical for image quality

Oct 25, 2009 at 12:14 PM

m-a-x
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p.8 #2 · FD 85L f/1.2: a real gem

Hello Alf,
I cannot add more information on the rear lens element than Ron already provided.
But regarding the aperture: I removed the whole ring where the big black lever is attached to. I think its purpose is only camera-lens communication within in a FD-body-lens-union.

In case you dismantled the lens body (unscrew the rear from the helix) you would exactly see how the silver lever works: it is attached to a ring wich is thin on one side and becomes continuously thicker. Let's call that shape a "ramp".
Depending on the position of the silver lever, the thicker or thinner part of the ramp is pushing another lever (yes, one more) directly at the aperture chamber. In other words: the ramp-shape which is attached to the silver lever is directly determining the opening and closing characteristic of the iris.
By the way, this last little lever directly at the aperture chamber is spring-loaded, and always pushing towards the ramp, closing the iris.
Now be careful: if you turn the silver lever too far (further than the f/1.2 position) the peak of the ramp is reached and will end abruptly. The spring loaded lever will be suddenly off the ramp in a position where it will not be possible to return onto the ramp, unless you can help with your hands.
That means in that case you had to open the lens body and to unscrew the helix.
Sorry that I cannot send a picture from that, since I don't want to disassemble it that far any more.

Oct 25, 2009 at 06:29 PM

Alf Beharie
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p.8 #3 · FD 85L f/1.2: a real gem

m-a-x wrote:
Hello Alf,
I cannot add more information on the rear lens element than Ron already provided.
But regarding the aperture: I removed the whole ring where the big black lever is attached to. I think its purpose is only camera-lens communication within in a FD-body-lens-union.

Then you must have removed the ring with all the tiny ball bearings on it?

Oct 25, 2009 at 06:44 PM

m-a-x
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p.8 #4 · FD 85L f/1.2: a real gem

Yes, there were many bearings. I removed them all.
However, I don't know if there is also a way to convert the lens by just leave the other ring, like you mentioned before...

Oct 25, 2009 at 07:23 PM

ronchappel
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p.8 #5 · FD 85L f/1.2: a real gem

kf_tam wrote:
For my 1Ds II, I get the following measurement:
EOS flange to metal top (in front of focus screen): 6.8mm
EOS flange to mirror front (when mirror is up): 7.3mm

...................Next I use a 3M scotch tape stick on the front of rear element.........

............................................. But unfortunately since I only tape the rear element and not the 2nd element, with all this head to head collision (and sometimes I turned the M42 adapter when it was topping the 2nd element) I caused a slightly smearing of the coating on the elements

. But this is a small price to pay for getting infinity.

If i understand this right you did always have at least one layer of tape between the last 2 elements?If so then the smearing is almost certainly gum from the tape-it should easily come off

I finally found my notes from when i measured the 5d mirror clearance:

EOS flange to mirror front (when mirror is up): 7.2mm
I also measured the mirror when it was partly down ,at a slight angle.At this point it has LESS clearance because the mirror is thick and so one edge naturally comes closer to the mount at that point.here it only gives 6.8mm ! (please note i cant remember what method i used to measure these.allow 0.1mm inaccuracy to be safe)
These numbers tally up well with actual testing.If i have my rear element set much more than 6.5mm back from the EOS mount surface,the mirror starts brushing it

Your claim that you've achieved infinity focus with a 1 series body got me thinking about all this recently.I wondered how accurate my rear element setting was and could i perhaps position it any closer to the 2nd last element.(some may remember i claimed to have them within 'less than' 0.5mm of each other without them touching)
After abit of thought and experimentation i managed to find a way of more accurately testing the gap between them!

First i must explain that my rear element holder has a slight forward extension which contacts the outer edge of the 2nd last element,stopping the glass parts of the two elements from touching.The point is-is this extension too long?

To test it i did the following:
I stuck a tiny piece of tape in the middle of the 2nd last element.When i tried to push the rear element assy against the 2nd last element nothing happened.

But when i tried two layers of this tape i could (*just*)rock the rear assy side to side.It was contacting the tape in the middle before the edges could seat properly.Also if i did try to press harder i could see the tape darken slightly as it was compressed.
Not believing it could be that clear i did this several times but it was the same every time.
After measuring the tape thickness i knew the gap had to be between 0.12mm and 0.24mm .
And due to the easily noticeable rocking motion i mentioned in the testing above ,it's most likely closer to the lower number.
So.. less than 1/4 of a mm gap! Pretty cool huh?

Since then i've had a little time to experiment with how far i can move the rear element forward and still achieve genuine infinity focus.
Sadly it seems to be no less than exactly 7mm -which is likely just a little too much for use on a 5D

When the brother visits with his 5D body this weekend i'll try it again but from past experimentation i'm guessing it wont work

Oct 27, 2009 at 02:05 PM

ronchappel
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p.8 #6 · FD 85L f/1.2: a real gem

haha! and i thought i was doing well to get the gap to about 0.17mm

I checked out your link to the contax compatibility list.Thats very interesting!
When i saw our comparative 7.2/7.3 measurements i had some doubts that the 1D could be better than the 5D,but the list seems to confirm your thoughts.I hope so anyway!
I'll try to find someone around here willing to let me try the lens of their camera

kf_tam wrote:
Hi Ron,

Mine protrudes only about 6.9mm, and the two rear elements separates only less than 0.1mm at infinity (but more than 0.05mm). I placed a 3M tape (0.05mm) and a 3M Post-it sticky paper (0.1mm) alternatively between the elements to test the minimum separation when I was setting the infinity limit.

Best Regards,
Edward Tam
.........

Oct 27, 2009 at 02:12 PM

ronchappel
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p.8 #7 · FD 85L f/1.2: a real gem

Alf Beharie wrote:
Then you must have removed the ring with all the tiny ball bearings on it?

Unfortunately it's been awhile since i first took one apart so i'm guessing a little.However the following should be pretty definite ..

-certainly anything behind the rear chassis mount points can be removed.only keep the rear element
-all the small bearings,and anything holding them or attached to them can be removed
-the only aperture activation lever you need is the one directly attached to -and part of- the main lens barrel assy.It's the actual one that activates the diaphragm and should be silver colored.It has a lever that sticks up beside the smaller rear lens barrel
You have to make some kind of link directly from the aperture ring at the rear of the lens to this lever

Just a thought... did you say your diaphragm didnt move? The lever i just mentioned has a cam around it's base which contacts a small black plastic thing(the diaphragm activator).If this thing has run PAST the highest spot on the cam,it will be sitting in a dead zone where moving the lever does nothing

Oct 27, 2009 at 03:00 PM

Alf Beharie
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p.8 #8 · FD 85L f/1.2: a real gem

Thanks Ron..I'll have to check that out.

Oct 27, 2009 at 04:31 PM

kf_tam
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p.8 #9 · FD 85L f/1.2: a real gem

Alf, here is Taiwan's Bigeye FD 85L to EOS conversion. While the text is Chinese, the pictures themselves should provide good reference for you.

Too bad this was not published before I did mine. I ended up with many tiny bearing balls fallen inside the focusing helical, and I had to completely disassemble the lens to take out all the balls. A magnet and a magnetize screwdriver was a big help here. I also took the chance to relube the lens.

Alf Beharie wrote:
Thanks Ron..I'll have to check that out.

Edited on Oct 30, 2009 at 02:07 PM · View previous versions

Oct 29, 2009 at 11:49 AM

kf_tam
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p.8 #10 · FD 85L f/1.2: a real gem

ronchappel wrote:
If i understand this right you did always have at least one layer of tape between the last 2 elements?If so then the smearing is almost certainly gum from the tape-it should easily come off

Yes, but you should know that the coating itself has limited hardness. And I did press (lightly) and rotate the element to check for direct contact. So even after washing with ethanol the mark is still there.

ronchappel wrote:
I finally found my notes from when i measured the 5d mirror clearance:

EOS flange to mirror front (when mirror is up): 7.2mm
I also measured the mirror when it was partly down ,at a slight angle.At this point it has LESS clearance because the mirror is thick and so one edge naturally comes closer to the mount at that point.here it only gives 6.8mm ! (please note i cant remember what method i used to measure these.allow 0.1mm inaccuracy to be safe)
These numbers tally up well with actual testing.If i have my rear element set much more than 6.5mm back from the EOS mount surface,the mirror starts brushing it

Well, I also found that when the element approaches 7mm protrusion it would collide with the mirror of 1Ds Mk2. But I have seen remarks that the 1D series retracts the mirror towards the sensor when it is swinging up. When I manually move the mirror up there is really some backward movement. So this may be the real reason why 1D series is better than 5D in alt. lens compatibility.

ronchappel wrote:
First i must explain that my rear element holder has a slight forward extension which contacts the outer edge of the 2nd last element,stopping the glass parts of the two elements from touching.The point is-is this extension too long?

I use flange-less M39 to M42 adapter, and the 2nd element can pass through its opening well enough to collide with the 1st element.

ronchappel wrote:

After measuring the tape thickness i knew the gap had to be between 0.12mm and 0.24mm .
And due to the easily noticeable rocking motion i mentioned in the testing above ,it's most likely closer to the lower number.
So.. less than 1/4 of a mm gap! Pretty cool huh?

Since then i've had a little time to experiment with how far i can move the rear element forward and still achieve genuine infinity focus.
Sadly it seems to be no less than exactly 7mm -which is likely just a little too much for use on a 5D

When the brother visits with his 5D body this weekend i'll try it again but from past experimentation i'm guessing it wont work

From my record, infinity can be achieved with 6.9mm protrusion when the element separation is slightly larger than 0.05mm (more than one layer of tape thickness but less than 2). YMMV

p.s, Just got the FD 55/1.2 aspherical, I am depending on the mercy of my 1Ds2 mirror again

Edited on Oct 29, 2009 at 12:33 PM · View previous versions

Oct 29, 2009 at 12:14 PM

kf_tam
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p.8 #11 · FD 85L f/1.2: a real gem

Sorry, but 0.17mm simply would not cut it even for a 1Ds

.
But setting the elements this close is potentially hazardous for the lens. When the lubricant drys or loose, the helical would have enough play to cause a "hard" collision. Or if the lens is rocking during a trip....

Last Saturday I opened a Contax 35/1.4 to relube the helical, because there was very significant play. When I focused the lens to infinity, I found that at wide open somethimes the zone B (a reference from 16-9.net) was sharp and sometimes it was not. So I tried taking an image while pressing the lens towards camera, and another while pulling the lens towards the subject. The sharpness at Zone B differed (pressing was much better) while Zone A and C I noted no significant changes. I disassembled and found the lubricant has hardened (but the focusing was always smooth). I relubed the lens, and the lens has no significant play now, and the sharpness at Zone B is more consistent now (after playing with the floating front element for some time

)

ronchappel wrote:
haha! and i thought i was doing well to get the gap to about 0.17mm

kf_tam wrote:
Hi Ron,

Mine protrudes only abou 6.9mm, and the two rear elements separates only less than 0.1mm at infinity (but more than 0.05mm). I placed a 3M tape (0.05mm) and a 3M Post-it sticky paper (0.1mm) alternatively between the elements to test the minimum separation when I was setting the infinity limit.

Best Regards,
Edward Tam
.........

Oct 29, 2009 at 12:31 PM

Alf Beharie
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p.8 #12 · FD 85L f/1.2: a real gem

kf_tam wrote:
Alf, here is Taiwan's Bigeye FD 85L to EOS conversion. While the text is Chinese, the pictures themselves should provide good reference for you.

Too bad this was not published before I doing mine. I ended up with many tiny bearing balls fallen inside the focusing helical, and I had to completely disassemble the lens. But it may be a good practice to relube old lens.

Alf Beharie wrote:
Thanks Ron..I'll have to check that out.

Thanks K!....Are you able to read and write Chinese by any chance?...If so could you please try to contact him and ask him the exact dimensions of his custom made Copper fork bracket, which he has screwed onto the aperture dial...Heres a pic showing the fork on the dial:

This image is copyrighted by the owner

It would be great if these forks could be mass produced to make it really easy for others wanting to convert the FD 85mm f1.2 L in future.

Oct 29, 2009 at 10:08 PM

kf_tam
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p.8 #13 · FD 85L f/1.2: a real gem

While I can read Chinese, but as far as I read he doesn't own the lens. So if he didn't leave any notes, the information is lost. I will ask in his blog, but don't hold your breath.

In his text, he told he has carefully trimmed the dimension until
1. it fitted the aperture control lever.
2. its forward edge limit the aperture ring to not pass over F1.2 position.
3. its backward edge limit the aperture ring to not pass over F16 position.

Alf Beharie wrote:

Thanks K!....Are you able to read and write Chinese by any chance?...If so could you please try to contact him and ask him the exact dimensions of his custom made Copper fork bracket, which he has screwed onto the aperture dial...Heres a pic showing the fork on the dial:

This image is copyrighted by the owner

It would be great if these forks could be mass produced to make it really easy for others wanting to convert the FD 85mm f1.2 L in future.

Oct 30, 2009 at 04:58 AM

Alf Beharie
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p.8 #14 · FD 85L f/1.2: a real gem

kf_tam wrote:
While I can read Chinese, but as far as I read he doesn't own the lens. So if he didn't leave any notes, the information is lost. I will ask in his blog, but don't hold your breath.

In his text, he told he has carefully trimmed the dimension until
1. it fitted the aperture control lever.
2. its forward edge limit the aperture ring to not pass over F1.2 position.
3. its backward edge limit the aperture ring to not pass over F16 position.

Thats why knowing the dimensions he ended up with is very important...I dont fancy having to cut umpteen of these forks out of copper sheet, all with slightly different dimensions, till I find the size thats correct for the job. Lifes too short!

Oct 30, 2009 at 06:55 AM

ronchappel
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p.8 #15 · FD 85L f/1.2: a real gem

kf_tam wrote:
Sorry, but 0.17mm simply would not cut it even for a 1Ds

That's very usefull definitive info,Thanks!

As mine has a stopper built in it will be safe to adjust them closer.

Not sure it helps or not,but you may want to try acetone (in tiny amounts!) or mineral turps to remove that mark.Don't worry,i've used both on my lens with no problems.One thing i've noticed over the years is that alcohol type lens cleaning fluids are almost useless at removing gum or grease.
Hopefully it's not a permanent mark!

It's also interesting what you said about the 1Ds mirror moving backwards slightly.I'd heard that some cameras do such things and did wonder if that may possibly explain things

Oct 30, 2009 at 10:57 AM

ronchappel
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p.8 #16 · FD 85L f/1.2: a real gem

Alf Beharie wrote:

Thats why knowing the dimensions he ended up with is very important...I dont fancy having to cut umpteen of these forks out of copper sheet, all with slightly different dimensions, till I find the size thats correct for the job. Lifes too short!

Its interesting WHERE he's mounted that one.The square plastic bump it wraps around makes it easy to duplicate the position.
The gap between the tabs is critical but relatively easy to get right.
The length is not so hard either-just make them too long and trim to size last.
Unfortunately the positioning of the gap between the tabs is super critical and really tricky to get right(so the diaphragm is exactly fully open @ f1.2).Obviously you could mount it by elongated holes for adjustability but it wants top be a reliable setup.Personally i've never been able to make such small screws work well with enlarged holes

!
Added to that is the issue of how you get it the right distance away from the ring-you need adjustability that way also!

Personally i feel its far easier to use stiff wire 'tabs' instead.Just bend em to shape! Only the tips of them contact the lever so it's so easier to get right.
Still annoying tho...

This image is copyrighted by the owner

Oct 30, 2009 at 11:30 AM

m-a-x
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p.8 #17 · FD 85L f/1.2: a real gem

The different methods are very interesting!

This part is one of the issues which make the conversion difficult.
Yes, it is annoying but it is a challenge as well.
If it would be that easy, everybody had a converted one ;-)

Oct 30, 2009 at 01:09 PM

kf_tam
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p.8 #18 · FD 85L f/1.2: a real gem

Alf Beharie wrote:
kf_tam wrote:
While I can read Chinese, but as far as I read he doesn't own the lens. So if he didn't leave any notes, the information is lost. I will ask in his blog, but don't hold your breath.

In his text, he told he has carefully trimmed the dimension until
1. it fitted the aperture control lever.
2. its forward edge limit the aperture ring to not pass over F1.2 position.
3. its backward edge limit the aperture ring to not pass over F16 position.

Thats why knowing the dimensions he ended up with is very important...I dont fancy having to cut umpteen of these forks out of copper sheet, all with slightly different dimensions, till I find the size thats correct for the job. Lifes too short!

Well, Jeff (Bigeye) has kindly replied that he didn't leave behind the dimensions, but it should be easy to measure the approximate dimensions that is required if you examine the lens, and trim the size slightly to fit your need

. Some patience is required, though.

Well, my attempt just fullfills requirement 1, the aperture ring can turn slightly pass f1.2 and f16. But I wouldn't loss any sleep for these, anyway.

I nearly finish converting the FD 300/2.8 SSC fluorite to M42 mount (mainly for astronomical imaging), And I did make the aperture lever three times until I got it right. I lost a lot of sleeping time for this

Oct 30, 2009 at 01:56 PM

kf_tam
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p.8 #19 · FD 85L f/1.2: a real gem

ronchappel wrote:
Not sure it helps or not,but you may want to try acetone (in tiny amounts!) or mineral turps to remove that mark.Don't worry,i've used both on my lens with no problems.One thing i've noticed over the years is that alcohol type lens cleaning fluids are almost useless at removing gum or grease.
Hopefully it's not a permanent mark!

Thanks for the advice, I should try some acetone tonight.

Oct 30, 2009 at 02:00 PM

Alf Beharie
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p.8 #20 · FD 85L f/1.2: a real gem

kf_tam wrote:
Alf Beharie wrote:
kf_tam wrote:
While I can read Chinese, but as far as I read he doesn't own the lens. So if he didn't leave any notes, the information is lost. I will ask in his blog, but don't hold your breath.

In his text, he told he has carefully trimmed the dimension until
1. it fitted the aperture control lever.
2. its forward edge limit the aperture ring to not pass over F1.2 position.
3. its backward edge limit the aperture ring to not pass over F16 position.

Thats why knowing the dimensions he ended up with is very important...I dont fancy having to cut umpteen of these forks out of copper sheet, all with slightly different dimensions, till I find the size thats correct for the job. Lifes too short!

Well, Jeff (Bigeye) has kindly replied that he didn't leave behind the dimensions, but it should be easy to measure the approximate dimensions that is required if you examine the lens, and trim the size slightly to fit your need

. Some patience is required, though..

Oh well, guess I'll just have to experiment with the dimensions.

I nearly finish converting the FD 300/2.8 SSC fluorite to M42 mount (mainly for astronomical imaging), And I did make the aperture lever three times until I got it right. I lost a lot of sleeping time for this

.

It would be interesting to know how the FD 300/2.8 SSC fluorite compares to the Tamron SP 300mm f2.8 LD IF (60B)?

Oct 30, 2009 at 06:02 PM

kf_tam
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p.8 #21 · FD 85L f/1.2: a real gem

Alf Beharie wrote:

Oh well, guess I'll just have to experiment with the dimensions.

Good luck

It would be interesting to know how the FD 300/2.8 SSC fluorite compares to the Tamron SP 300mm f2.8 LD IF (60B)?

But who would buy the Tamron when the Canon FD 300 f2.8 L and SSC Fluorite can be had for the same price or less? My Fluorite is very slightly scratched and is only US$377, and a L with a slightly fungus spot is heading my way for just US$517. And recently two very good quality 300/2.8 Fluorites were sold for just US425 and 5xx. Poorer condition Nikkor AIS 300/2.8 ED lenses were sold for US600~800. Tamrons were also selling for about US600-900.
Due to the "difficulty" of mount conversion, the FD 300/2.8s are the best bargain for EOSers (with conversion ability)

.

p.s. For all the money I spent on the two FD300/2.8s, I could also buy a single EF300/2.8 non-IS with malfuntions (a failed USM or loosen internal element). But I judged the risk was too high for the price.

Oct 31, 2009 at 03:37 AM

gcrimmins
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p.8 #22 · FD 85L f/1.2: a real gem

It would be interesting to know how the FD 300/2.8 SSC fluorite compares to the Tamron SP 300mm f2.8 LD IF (60B)?

I've used the Tamron 60B as well as the FD 300/2.8L, and both versions of the EF 300/2.8. The Tamron is a nice sharp lens, but the canon is noticeably better. Images from the Canon just have a crispness and sparkle you don't get with the Tamron.

--Geoff

Oct 31, 2009 at 04:12 AM

Alf Beharie
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p.8 #23 · FD 85L f/1.2: a real gem

I could'nt find any 300mm f2.8 lenses on ebay UK for under £500, so when I found a camera shop in London selling a Tamron SP 300mm f2.8 LD IF (60B) in good cosmetic condition and with mint optics for less than £350 I snapped it up!
The Tamron SP BBAR 2x teleconverter is a very good match for the SP 300/2.8 LD IF and it does'nt noticably increase CA. I did try a Nikon TC-300 2x TC on it and the CA it produced was terrible so I returned it and stuck with the BBAR.

Oct 31, 2009 at 08:44 PM

Alf Beharie
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p.8 #24 · FD 85L f/1.2: a real gem

****Progress update****...After reading how this guy converted his FD 85mm f1.2 L to EF mount (translated from Chinese):

http://babelfish.yahoo.com/translate_url?doit=done&tt=url&intl=1&fr=bf-home&trurl=http%3A%2F%2Fwww.bigeye.url.tw%2Fbig5%2Fd_ca85_12.htm&lp=zt_en&btnTrUrl=Translate

The most usefull piece of info I found in the whole article was how he made a fork actuator bracket that screws onto the aperture dial and moves the Iris actuation lever, as can be seen here:

This image is copyrighted by the owner

Tonight I set about making one myself which is'nt as easy as it looks. In fact its an extremely skillfull bit of engineering.
To make it I first had to make some suitable copper sheet and I did this cutting a 1 1/2-2" length of 15mm copper tube down one side, annealing it with a blowtorch, opening it out with pliers and then hammering it flat.
Then I marked the required outline on the sheet and with great care and precision I accurately cut out the shape with a pair of tinsnips. Some carefull filing was necessary to get the outer radus of the brackets securing flange to perfectly match the inner radius of the aperture dial.
Next I needed to drill two tiny holes through both the fork bracket and the aperture dial. The two holes in the bracket were then drilled slightly larger than in the aperture dial to give clearance for the securing screws to pass through freely whilst tightening into the aperture dial underneath. The screws I chose were tiny (about 1-1.2mm, corse threaded and about 3mm long. This turned out to be too long so I had to grind them down to about 2mm long using a custom jig and an angle grinder.
Then using a machine vice I accurately bend each fork leg at right angles to the securing flange. At this point I added an improvement over the orginal design...I bent about 1.5-2mm of the end of each fork arm back outwards at right angles (towards the middle of the lens) to ensure a positive catch on each side of the Iris actuation lever.
I gradually snipped the copper away on each side of the securing flange of the bracket to get the aperture dial to stop in the correct position when I noticed that only one side of the bracket was actually acting as a stop!
It turned out that the left hand side of the flange sets the f16 stop position and the f1.2 position was set by a cutout on the aperture dial itself. So using a file I gradually filed this cutout a bit longer until the f1.2 position was set bang on.
Then it was a simple case of screwing the backplate on to keep the aperture dial in place and the lens now stops down and opens up perfectly with a lovely snappy action!!!

Next job is to fit an SA mounting plate to it. Thats going to be a bit tricky too as a quick test showed that closest focus distance is reached with the rear of the lens about 40-45mm away from the mount on the camera...WTF!!!!!!

Nov 04, 2009 at 01:09 AM

ronchappel
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p.8 #25 · FD 85L f/1.2: a real gem

Alf Beharie wrote:
...... At this point I added an improvement over the orginal design...I bent about 1.5-2mm of the end of each fork arm back outwards at right angles (towards the middle of the lens) to ensure a positive catch on each side of the Iris actuation lever.

Yep,good move!

Alf Beharie wrote:
...........Next job is to fit an SA mounting plate to it. Thats going to be a bit tricky too as a quick test showed that closest focus distance is reached with the rear of the lens about 40-45mm away from the mount on the camera...WTF!!!!!!

Closest focus?thats abit confusing .it's natural for lenses to focus closer as you move them further from the camera.To test it you will need to set the lens to infinity and see if it can focus on a distant subject.That's the only accurate way of doing it.

Is the fixed rear element set the right distance from the sensor plane?It's important to get that right first.The rear edge should protrude 7.4mm INSIDE the camera,measured from the camera mount surface.If it's less than 7mm you will only be able to focus close.

mmm, i hope that rear element is the right one...

Nov 04, 2009 at 01:32 AM


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