PDA

View Full Version : First of the Avenon's!


pfogle
04-18-2005, 13:47
Thanks to the efforts of Mike, see here (http://www.rangefinderforum.com/forums/showthread.php?t=5408) I now have the Avenon 21/2.8 :D

First impressions - I like the physical presence of this lens... pretty big, but sturdy. Excellent build and silky focus - like R/F Canon or Nikon.

Wide open, pretty soft, but it begins to catch the CV at f4 in the centre, and is a close match at f8, even at the edges in the R-D1. A big issue is flare... I'm going to put a rubber shade on it, as it really needs something. Makes a very nice b/w image.

If anyone wants a mint CV 21/4, let me know!

cheers
Phil

jlw
04-18-2005, 14:06
How's the focusing accuracy? Seems to have been some collective nervousness about this...

pfogle
04-18-2005, 14:26
Looks spot on to my informal eye... I did a flower at 2.8 at about a meter, and it was fine. At f4 there's plenty of leeway. R/F finds infinity OK.

pfogle
04-18-2005, 17:11
My last post was completely wrong :(

Looking a bit more carefully, I find the Avenon 21/2.8 front focuses by about 12cm at 1m distance - that's quite a lot.

My Ultron front focuses by about 2cm at 1m.

Shame about the Avenon: any ideas?

Phil

mtokue
04-18-2005, 19:43
Phil, If you can try a different L-M adapter I believe this will make a difference.
I have also started to knowtice that the lens sits differently on different adapters.
What I'm trying to convey, is that on different adapters the position that infinity sits on
top of the lens is different, ie it is not quite in the middle when looking at the camera from above.and this varies with different adapters, now in my mind the degrees that this is "off"
by would relate proportunately with the amount that the plane of focus on the sensor is "off" thus causing front focusing in various degrees.
My canon LTM also does not sit "in the middle" either but as it is a 50mm I don't think the effect is that knowticeable, but the effect is somewhat magnified in wides and teles.
Sorry, does that make sense?
Mike.

jlw
04-18-2005, 21:09
I have also started to knowtice that the lens sits differently on different adapters.
What I'm trying to convey, is that on different adapters the position that infinity sits on
top of the lens is different, ie it is not quite in the middle when looking at the camera from above...Sorry, does that make sense?
Mike.

Sorry, I'm not sure I understand this...

Do you mean that when viewed from above, the lens is not centered side-to-side in the camera lens mount? If so, that WOULD be a big problem!

But if you just mean that the focusing index (and infinity mark, if the lens is set to infinity) is not on top of the barrel, I think that's normal -- at least for some lenses.

Here are some pictures of a few Canon LTM lenses on various camera bodies. Notice that all of them have the index mark in about the same position, which is NOT on top of the barrel. On all of them, the index mark lines up toward the rangefinder window, rather than being on top.

http://homepage.mac.com/jlw/images/canon-infinity/50-14_on_P.JPG
http://homepage.mac.com/jlw/images/canon-infinity/50-14_on_RD1.JPG
http://homepage.mac.com/jlw/images/canon-infinity/100-2_on_P.JPG
http://homepage.mac.com/jlw/images/canon-infinity/50-095_on_7s.JPG

All my Canon LTM lenses do this, so I had always assumed Canon made them that way on purpose. I think the idea was to make it easier to check the focusing distance when holding the camera up to your eye. With the mark facing the rangefinder window, all you would have to do is lower and tip the camera slightly to see the mark. If the mark were on top, you would have to twist the camera more.

Now, I don't KNOW whether or not the Avenon lens is designed the same way! If it is not, then this could be a cause of rangefinder coupling error -- the coupling ring or tab on the back of the lens might not be lining up squarely with the follower arm in the camera body. In that case, a different adapter might solve the problem.

It also would be interesting to check the lens on a screwmount camera, to see whether the adapter is in fact the source of the problem. As you have noted, with a lens of such short focal length, a small thickness variation in the adapter would still be a large percentage of the focal length, so would have a proportionally larger effect.

I'm sure we will be able to get a more accurate fix on this situation as more of us receive our Avenon lenses. It may be that all others are fine, and Phil's run of bad luck with R-D 1s is just continuing with lenses! Phil, you haven't broken any mirrors lately, have you?

mtokue
04-18-2005, 21:41
Yes, thats exactly what I was trying to say, but as I'm at work could not use photos to show.
My canon on a L-M adapter does the same as your photos but the Avenon sits to the right from a few degrees to upto 10-15 degrees (Dependant on adapter).
I haven't been able to test thouroughly so I found the adapter that lets the lens sit as near to the top as possible and have been using that adapter.
To me there must be a difference, and I would imagine that this could be an area that needs to be examined more closely.
Just not quite sure of the best method to go about this. ideas?
Mike.

pfogle
04-19-2005, 03:24
My first calculation suggests that the plane of focus is about 1/20th mm out. That's about a third of a turn of the L39 thread, which has a pitch of 0.75mm, so I doubt if it's just the position of the lens. I'll see if I can get someone to grind that amount off an adaptor, and see if it works.

Trouble is, it's hard to estimate what effect that will have on focus at other distances, ie at infinity. Probably won't hurt though!

More news soon...
cheers
Phil

tom_f77
04-19-2005, 03:33
My first calculation suggests that the plane of focus is about 1/20th mm out. That's about a third of a turn of the L39 thread, which has a pitch of 0.75mm, so I doubt if it's just the position of the lens.
Phil

Phil,

Have you done the same calculation for the smaller error with the Ultron and tried some of your other lenses?

Just wondering if it's possible that the smaller error with the longer focal length might correspond to the same error - then it might just be a rangefinder calibration issue?

Tom

pfogle
04-19-2005, 04:13
Hi Tom... I'll check this... as you say, the errors are pretty consistent.

Thing is, of course, all the lenses are slightly different. I've noticed no trouble with the M-mounts (40/1.4 that you now have, 50/2 Hexanon) so I'm hesitant to start playing with the R/F. But it's probably worth taking it in for a checkup. Also, I don't see the same thing with the 21mm CV, as far as I can tell.

Does anyone know whether Sendean in London would be up to dealing with the R-D1?

I'll have to do some more careful tests.... <sigh>

cheers
Phil

mtokue
04-19-2005, 04:48
Phil , Just for the sake of data/info do you have a PS digital that you could take a snap
of the top of the camera so that we can compare how the lenses sit with our adapters?
The attach shows the best one that I have found so far, probably just a few degrees
The worst that I have tried is literally so far to the right that you can not see what fstop you are using from the top.
Mike.

mtokue
04-19-2005, 05:22
Yeee Haaa, :D :D :D
Sorry bout that its just that I've got a friend over and I was telling him the problems when he dug out his camera and told me to try his adapter.
And guess what! His adapter alligns the lens dead centre!!! :eek:
And his lens (Canon 50 f1.8) works fine with my adapter so we have just swapped.
Now I guess I'll have to check whether this has fixed the slight front focus.
The Attached is in following order
1 = Newly aquired good adapter ( Old Leitz original M2 M3 135mm) :D
2= My worst adapter (Made by Avenon but for their 28mm) :(
3 = Silver lens with my best adapter non brand
Now if you look at the base of the lens actually at the adapter you can see the dip
and above is where the red triangle shood be. Look at the difference. Am I jumping to conclusions or could this be the problem?
Mike.

pfogle
04-19-2005, 05:38
Mike, my setup is like your middle thumbnail.
If the difference is 30deg rotation (seems about right in worst case) then that would be equivalent to 1/12 of 0.75mm - 0.0625mm, which isn't far off what I figured the error in the focus to be (my guess was about 0.05mm)

So, yes, the adapter may well be the problem. I'll try swapping them around when I get a chance. All my adapters are CV ones.

I'm at work (believe it or not) at the moment, so I won't be able to sort this out until I get home.

Phil

Jim Watts
04-19-2005, 05:42
My 21mm Avenon f/2.8 has just arrived. Thanks again Mike.

Build, feel and finish is good and as Mike and Phil have described. It does front focus a little close-up. At 1 meter I think the sharpest plane is about 5 - 7 cm forward at f/2.8 on repeat tests. The (rangefinder) focused point is still acceptably (to me) sharp at this distance and aperture, but it falls off very quickly behind, so I think its probably comparable to Mikes own sample in this respect and better than with the same problem on my 35mm f/2 Cron. The DOF being more on this lens and helping to cover any problem.

I don't think I see any focus problems at infinity as per Dave's posts and it seems only a little soft at full aperture, but I don't have another 21mm to compare with. Vignetting is quite low. Nothing to give me any worries and should be easily correctable in Epson Raw if your a pefectonist.

With my VC 35/135 adapter the focusing index is only a few degrees from vertical. It align's with the right-hand edge of the rangefinder window (camera viewed from front). Its no way as far over as jlw's Canon lenses shown above. Fitting it with the same adapter to my M4 shows the same few degrees error. Rangefinder seems to focus to the same spot as on the R-D1 but I have no film results yet to see if there is any focus error on this camera.

Generally I'm very pleased with this lens and think I can live with the slight front focus. More so than with my Cron where it is still more than usable.

Sorry the compatibility on yours seems a bit worst Phil. Sendean is quite helpful and have years of experience with many different rangefinder cameras, but I doubt if they have worked on an R-D1 yet, but as the mechanical side is close to the Bessa R3A it might be worth going to have a chat with them.

Jim Watts
04-19-2005, 05:57
I handn't seen Mikes picture examples above when I posted.
Index mark on my adapter is between 2 & 3 on Mike's examples, closer to 3. Left point of base of index triangle alines with right edge of cut out when viewed in same way from above.

jlw
04-19-2005, 06:00
Wow, I didn't realize there was such a wide variation in the indexing positions of various screw-to-bayo adapters!

It makes me wonder what would happen if somebody used one with a tele lens -- since these usually have an RF coupler that's just a tab, rather than a ring that goes all the way around.

Some of these adapters look to be so far off that the tab might miss the camera's RF coupler arm entirely!

Does the Avenon lens have a tab, or a ring? Even if it's a ring, I wonder whether a drastically mis-indexed adapter might put the ring far enough out of position that the coupler arm no longer hits in the right place. This could be enough to cause focusing errors, either with or without the effect of the adapter's screw pitch.

Oh, well, another day, another can o' worms...

mtokue
04-19-2005, 06:15
FYI,
Attached Pic of the rear of two avenons the black has the L-M attached the silver is
without. the RF Coupling is a brass ring.
Mike.

Charles D. Orze
04-19-2005, 07:04
I got my 21mm yesterday--thank you Mike! After the first post I checked my lens against my 28 ultron and at 100% side by side in photoshop. My focus is spot on accurate.

Best,

Charlie Orzech

mtokue
04-19-2005, 07:28
I am attaching pic of the adapter that works to put the lens dead centre
for me anyway. :D
I still don't know if this fixs the front focus but the few shots I have taken this evening look promising will test some more :rolleyes: .
Mike.
PS the right hand pic is a close up of the part that the flash blew out originally
Nikon coolpix PS = No Control.....