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Minolta 58/1.2 AF Conversion with ROM Chip - Build

Printed From: Dyxum.com
Category: Equipment forums
Forum Name: Other mount lenses
Forum Description: Discussions for non alpha mount lenses
URL: http://www.dyxum.com/dforum/forum_posts.asp?TID=29279
Printed Date: 13 November 2018 at 23:22


Topic: Minolta 58/1.2 AF Conversion with ROM Chip - Build
Posted By: Shaocaholica
Subject: Minolta 58/1.2 AF Conversion with ROM Chip - Build
Date Posted: 01 April 2008 at 10:43
Well, I've waited way too long to do this write up but I've found a few spare minutes tonight and I've already got the pictures "processed" so I might as well. Before, I begin I would like to thank:



Hotwire - For bugging me about f/1.2s for the past year

Pete Ganzel - For doing all the initial research and offering his services

JamesLaoT - For supplying a ROM Chip small enough to fit in the limited space on the f/1.2

Arkku - For his initial work on the same lens



So a few months back I decided to get a f/1.2 and convert it to AF mount. Little did I know I would eventually end up with 5 of the things (one busted) and end up converting the remaining 4. Since then I've sold one at cost to Hotwire who followed this project with me from day -1. I've got http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=130207528822" rel="nofollow - another one on ebay to raise some funds for my impending wedding. Now I have just 2 left, a 50/1.2 (latest style) and a 58/1.2 (all metal). These I plan on keeping since they produce slightly different images.



Here are the 5 lenses I started this project with:





I managed to get these all at bargain prices just due to dumb luck I guess since every time I checked ebay or craigslist, a new one would pop up for a ridiculous price. Once I got 5 I stopped as it was getting out of hand. However, I did have to swap some parts around since some of them were damaged but in the end I ended up with 4 good lenses.







Here's some shots of the 58/1.2 MC Rokkor Rubber Ring Version

After the Modification










The aperture blades show some wear from rubbing against each other but it doesn't seem to affect anything.

















This is an aftermarket square hood I got from http://www.fotodiox.com/shop/product_info.php?cPath=1_17_41&products_id=4118" rel="nofollow - fotodiox.com . It fits very nicely and is quite thicker than it looks. Really robust.





The chip installed actually reports a focal length of 60mm. Depending on which EV step you have selected, the camera will either show f/1.2(0.5EV step) or f/1.1(0.3EV step).











Here it is on the Minolta 7 film where it works the same way.











Here are some quick sample photos
















http://shaozhang.smugmug.com/gallery/4598419_HkpWc" rel="nofollow - Here is the full sample gallery of various quick snaps I've taken with both the 50/1.2 and 58/1.2



After I got all the lenses, I opened them up and cleaned out all the accumulated dirt, sand and dust. I also removed all the old grease and applied fresh synthetic Nyogel grease. I then swapped some parts around so that all the worst parts ended up on one bum lens making the best use of all the best parts amongst the 4 other lenses. I let Pete keep the bum lens. I figure if anyone can use those optics it would be him. I then sent them off to Pete Ganzel so he could machine 4 matching mounts for them all with the proper registration distance without using any shims. While they were at Pete's, I also ordered 4 ROM chips from JamesLaoT on this forum. Once I got the chips and lenses back, I attached the ROM chips to the mounts which you can read more about in the gallery linked below:



http://shaozhang.smugmug.com/gallery/4630693_jPsbU" rel="nofollow - Here is a full photo gallery of the build for the above lens



My Sony A700 has a http://www.katzeyeoptics.com/item--Sony-A700-Focusing-Screen--prod_A700.html" rel="nofollow - Katzeye split image screen installed which helps in using this lens tremendously. However, with the chip installed, focus confirmation works as well although I find the split image screen is much faster to use and much more accurate.



The main benefit of the chip for me is the enabling of SSS on Sony DSLRs. On my A700, I now have a f/1.2 lens I can also use SSS with. This is an awesome low light combination that no other system has right now. Sure the Canonites have their 50/1.2L but that lens isn't IS and they don't have in body IS either.



Here are some related links:

http://www.pbase.com/pganzel/modification_of__58mm_f12_rokkor" rel="nofollow - Pete's f/1.2 Mount Conversion thread

http://www.dyxum.com/dforum/forum_posts.asp?TID=27049" rel="nofollow - My previous f/1.2 thread

http://www.dyxum.com/dforum/forum_posts.asp?TID=19601" rel="nofollow - Arkku's 58/1.2 build thread

http://www.dyxum.com/dforum/forum_posts.asp?TID=21894" rel="nofollow - JamesLaoT's M42/ROM Chip sales thread



If you have any further questions about the lens and how it works, check out the http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&rd=1&item=130207528822" rel="nofollow - massive FAQ I wrote on the ebay page for one of them.



Replies:
Posted By: dogears
Date Posted: 01 April 2008 at 10:57
Kick @$$ lens|setup|sample images!!!

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http://shutteredlight.blogspot.com - woof!


Posted By: gsaronni
Date Posted: 01 April 2008 at 11:16
Incredible work. I really like the A700 with this huge glass, and I think the ROM chip comes from a 85/1.4 lens, it is the smallest chip I have seen

Regards

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35/1.8 | 50/1.4 | 50M | 100/2
CZ 16-80 | Tamron 70-300 USD
XZ-2 | A700 | A77 M2
http://www.flickr.com/photos/gsaronni/


Posted By: Shaocaholica
Date Posted: 01 April 2008 at 11:20
Originally posted by gsaronni gsaronni wrote:

Incredible work. I really like the A700 with this huge glass, and I think the ROM chip comes from a 85/1.4 lens, it is the smallest chip I have seen

The ROM chip is new. It might be the same size/design as the 85/1.4 chip but its definitely not salvaged from a 85/1.4.


Posted By: matthiaspaul
Date Posted: 01 April 2008 at 13:09
Thanks for sharing your 1,2/58mm experiences.
Originally posted by Shaocaholica Shaocaholica wrote:


The chip installed actually reports an aperture of f/1.1 and a focal length of 60mm. While these figures are not exact, they were the only options from JamesLaoT and all the combined research into reverse engineering the lens ID codes. f/1.2 and 60mm are probably impossible and my guess is that Minolta never really intended or guessed they would need those exact figures for its AF lenses back in 1985.

At least some camera bodies should support aperture values between "1.0" (0 Av) and either "64" (+12 Av) or "90" (+13 Av) in 1/4 EV, 1/2 EV or 1/3 EV steps according to the following table, which was compiled from various sources:

http://www.mi-fo.de/forum/index.php?showtopic=10426&view=findpost&p=122551 - http://www.mi-fo.de/forum/index.php?showtopic=10426&view=findpost&p=122551

The internal representation is in 1/8 EV steps (binary values in the 5th column in the above-mentioned table).

Apertures displayed in 1/4EV steps (4th column) are only supported by the Minolta 9000 AF with Program Back Super 90 or Bulk Film Magazine EB-90, or by the Minolta 7000 AF with Program Back Super 70. Apertures given in 1/4EV steps follow some odd notation, where the aperture is given in 1 EV granularity (1st column) followed by a suffix 0, 1, 2 or 3 for +0/4EV, +1/4EV, +2/4EV or +3/4EV.

Apertures displayed in 1/3EV (3rd column) are supported by newer models (since the advent of the Dynax 9, IIRC).

The largest aperture value I have seen myself so far was "1.4" (PBS-90: "1.4_1") with my Minolta AF 1,4/50mm (in this case with a binary value of 25, not 24, as one would expect), the slowest aperture was "64" (PBS-90: "45_3") with my Minolta AF 3x-1x Macro Zoom (binary value 111, not 112). The largest value found in the Dynax 9 service manual and the Dynax 7D firmware is "1.0". The slowest value found in the Dynax 9 service manual is "64", in the Dynax 7D firmware it is "90".

Sometimes, aperture values are rounded for display, for example binary value 30 is displayed as "1.7" on the Dynax 9, not "1.8", as it should. The same goes for binary value 46 (shown as "3.5", not "3.6") and 50 (shown as "4.5" instead of "4.3") and 74 (shown as "13" instead of "12"). Since we don't have experiences with values faster than "1.4" yet, it is quite possible, that some of these values would be rounded in an odd fashion as well. This could explain the "1.1" display, assuming that all possible binary values have been tried already.
Still, at least on the Minolta 9000 AF with Program Back Super 90, it should be possible to tell apart apertures of "1.0", "1.1", "1.2" and "1.3". A true "1.2" aperture should be displayed as "1_2" (for 1 + 2/4EV corresponding with binary value 20), whereas a true aperture "1.1" should be displayed as "1_1" (for 1 + 1/4 EV, corresponding with binary value 18) instead.

Greetings,

Matthias

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Minolta-Forum (MiFo) - German forum for the Minolta, Konica, Konica Minolta and Sony world of photography: http://www.mi-fo.de" rel="nofollow - http://www.mi-fo.de


Posted By: Shaocaholica
Date Posted: 01 April 2008 at 22:42
Thanks for the explanation Matthias. Do you know why 58mm is also not a useable focal length?


Posted By: keith_h
Date Posted: 02 April 2008 at 00:12
Super job on these conversions. The word "craftsmanship comes to mind.

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http://gallery.heinrich.id.au - My gallery http://gallery.heinrich.id.au/gear - A700 x2, other stuff


Posted By: hotwire
Date Posted: 02 April 2008 at 03:24
Once again my thanks go out to Shao for his efforts on this.

Strangely, when mounted on my a700, the lens does in fact show a value of f/1.2. I do not know why it does this. When mounted on my M9, it shows a value of f/1.1.

For more of my experience with this lens, I have most (if not all of) my shots with this lens tagged appropriately: http://flickr.com/photos/34353273@N00/tags/minoltamcrokkor58mmf12/ - http://flickr.com/photos/34353273@N00/tags/minoltamcrokkor58mmf12/

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a99ii; Maxxum 9

CZ: 16-35, 24-70/2.8, 135/1.8; Minolta: 50/1.4; MC58/1.2; 85/1.4GD 300/2.8; 500/8; 600/4; Tam: 90/2.8M; Sig: 12-24/4.5-5.6; 15/2.8; Sony: 35/1.4G; 135STF, 70-200/2.8G


Posted By: hotwire
Date Posted: 03 April 2008 at 05:18
rovhazman on dpreview gets the hero cookie for why f/1.2 worked on my camera.

Set exposure steps to 0.5 ev instead of 0.3 ev for f/1.2 to show up instead of f/1.1 and f/1.3.

I just verified this also works with my maxxum 9.

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a99ii; Maxxum 9

CZ: 16-35, 24-70/2.8, 135/1.8; Minolta: 50/1.4; MC58/1.2; 85/1.4GD 300/2.8; 500/8; 600/4; Tam: 90/2.8M; Sig: 12-24/4.5-5.6; 15/2.8; Sony: 35/1.4G; 135STF, 70-200/2.8G


Posted By: polossatik
Date Posted: 03 April 2008 at 05:44
Marvelous... I really like stuff like this!

And congrats with the wedding also of course...

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7D / A580 and assorted lenses from 8mm fish to 1000mm / Minolta 7s Rangefinder /

HP Photosmart Pro B9180 In Da House!!


Posted By: brettania
Date Posted: 04 April 2008 at 16:11
This post and its predecessor must be setting some records for viewing -- 25 out of 105 on the site when I wrote this were viewing it. The two posts have had a combined hit rate of 3000+ views.

A tribute to the thoroughness of your presentation Shao.

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http://www.dyxum.com/dforum/posting-images-and-links-faqs_topic28010.html - Posting Images and Links | http://tinyurl.com/oz62mfp - Posts awaiting answers


Posted By: Arkku
Date Posted: 04 April 2008 at 17:23
Originally posted by brettania brettania wrote:

This post and its predecessor must be setting some records for viewing -- 25 out of 105 on the site when I wrote this were viewing it. The two posts have had a combined hit rate of 3000+ views.


Plus the 4700+ in http://www.dyxum.com/dforum/forum_posts.asp?TID=19601 - the older thread I posted and who-knows-how-many in Pete Ganzel's original. =)

Anyone notice that the prices of these lenses have at least doubled on eBay since these modifications appeared here? I got mine for 70 EUR, now they seem to be in multiple hundreds. I think we've destroyed the cheapness of used Rokkor glass. ;>


Posted By: matthiaspaul
Date Posted: 04 April 2008 at 18:44
Originally posted by Shaocaholica Shaocaholica wrote:

Thanks for the explanation Matthias. Do you know why 58mm is also not a useable focal length?


http://www.mi-fo.de/forum/index.php?showtopic=4477&view=findpost&p=50472 - http://www.mi-fo.de/forum/index.php?showtopic=4477&view=findpost&p=50472 [de]

In this posting your can find a table compiling a few values, I recorded when I had a closer examination of the Minolta 9000 AF flash protocol (almost 20 years ago. ;-) The focal length was non-lineary represented by a byte value, not a word or such. I had limited access to lenses in these days, so I recorded only these values:

35mm: 50 (32h)
50mm: 57 (39h)
70mm: 63 (3Fh) oder 64 (40h) with another lens
100mm: 72 (48h)
105mm: 73 (49h)
150mm: 81 (51h) or 82 (52h) with another lens
210mm: 89 (59h)

As you can see, there are at most six possible values between 50mm and 70mm. Focal lengths between 16mm and 600mm just won't fit into a byte value, no matter how hard you push. These were flash protocol values, but as discussed in this posting

http://www.mi-fo.de/forum/index.php?showtopic=14914&view=findpost&p=180793 - http://www.mi-fo.de/forum/index.php?showtopic=14914&view=findpost&p=180793 [de]

we found the lens protocol values to be binary identical.

Still, it is possible, that Minolta has added new ROM data entries with a finer granularity in more recent lenses, I don't know.

Sidenote: The binary values mentioned in my other post are meant to be flash-protocol values, too. The actual ROM values are given in 1/8 EV as well, but are shifted by an offset of 7 (or 8?), as we discussed in the same posting.

I would be interested, what a PBS-90 would display for your converted 1,2/58mm marvel, "1_1" or "1_2"? If you ever get a chance to find out ... ;-)

Greetings,

Matthias

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Minolta-Forum (MiFo) - German forum for the Minolta, Konica, Konica Minolta and Sony world of photography: http://www.mi-fo.de" rel="nofollow - http://www.mi-fo.de


Posted By: matthiaspaul
Date Posted: 04 April 2008 at 18:50
Originally posted by hotwire hotwire wrote:

rovhazman on dpreview gets the hero cookie for why f/1.2 worked on my camera.

Set exposure steps to 0.5 ev instead of 0.3 ev for f/1.2 to show up instead of f/1.1 and f/1.3.

I just verified this also works with my maxxum 9.

Thanks for this feedback, so I can flag these values as "confirmed" to be supported by the Dynax 9 in our aperture table over at MiFo. :-)

However, this does not explain the 1.1 display on "Shaocaholica"s Dynax 7, which was set to 1/2 EV according to the photos above (unless he changed the setting between the shots)...

Greetings,

Matthias

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Minolta-Forum (MiFo) - German forum for the Minolta, Konica, Konica Minolta and Sony world of photography: http://www.mi-fo.de" rel="nofollow - http://www.mi-fo.de


Posted By: Shaocaholica
Date Posted: 04 April 2008 at 20:15
Originally posted by matthiaspaul matthiaspaul wrote:


However, this does not explain the 1.1 display on "Shaocaholica"s Dynax 7, which was set to 1/2 EV according to the photos above (unless he changed the setting between the shots)...

I don't know where you are seeing 1/2EV on my 7. I have all my cameras set to 1/3EV and I just double checked my 7 this morning and it was set to 1/3EV. I set it to 1/2EV and it displayed f/1.2 correctly.


Posted By: matthiaspaul
Date Posted: 04 April 2008 at 20:43
Originally posted by Shaocaholica Shaocaholica wrote:

Originally posted by matthiaspaul matthiaspaul wrote:


However, this does not explain the 1.1 display on "Shaocaholica"s Dynax 7, which was set to 1/2 EV according to the photos above (unless he changed the setting between the shots)...

I don't know where you are seeing 1/2EV on my 7. I have all my cameras set to 1/3EV and I just double checked my 7 this morning and it was set to 1/3EV. I set it to 1/2EV and it displayed f/1.2 correctly.

Sorry, I must have been confused... I just cross-checked the colors of the exposure compensation dial on my Dynax 7 and I remembered them the other way around. Sorry for the confusion.

Greetings,

Matthias

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--

Minolta-Forum (MiFo) - German forum for the Minolta, Konica, Konica Minolta and Sony world of photography: http://www.mi-fo.de" rel="nofollow - http://www.mi-fo.de


Posted By: polossatik
Date Posted: 05 April 2008 at 18:38
you made it on http://www.hackaday.com !

http://www.hackaday.com/2008/04/03/custom-mounting-manual-minolta-sony-lenses/ - linky

sorry for the bandwidth Mladen, just could not resist to send that over;)

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7D / A580 and assorted lenses from 8mm fish to 1000mm / Minolta 7s Rangefinder /

HP Photosmart Pro B9180 In Da House!!


Posted By: Shaocaholica
Date Posted: 05 April 2008 at 18:52
Originally posted by polossatik polossatik wrote:

you made it on http://www.hackaday.com !

http://www.hackaday.com/2008/04/03/custom-mounting-manual-minolta-sony-lenses/ - linky

sorry for the bandwidth Mladen, just could not resist to send that over;)

Cool, thanks! I also made engadget yesterday which probably generated more traffic :P


Posted By: superx2won
Date Posted: 07 April 2008 at 07:53
shaocaholica, i checked the ebay today.. the bidding has gone crazy... with 2 day in remain for bidding, the bidding price has gone up to USD800+ ....I bet this price will go up till 1k USD.

With this price , i believe we can change job and become a full time MD len modifier .. haha..

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A900 + A65 + KM 7D + Maxxum 9 + S16-105
Learn repairing Minolta lens --> Join my http://www.photography-lab.com" rel="nofollow - Photography-lab.com blog for step by step guide


Posted By: dogears
Date Posted: 08 April 2008 at 12:46
@shao, my brother forwarded me the engadget link

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http://shutteredlight.blogspot.com - woof!


Posted By: Shaocaholica
Date Posted: 08 April 2008 at 17:42
Originally posted by dogears dogears wrote:

@shao, my brother forwarded me the engadget link

http://www.engadget.com/2008/04/04/minolta-lens-conversion-for-a700-with-rom-chip-keeps-focus-and-i/#comments - Here you go


Posted By: Cliff
Date Posted: 11 April 2008 at 16:58
Hi Guys, neat stuff. Where can I get chips and contact boards?

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ContaxRF, Min7000i, Sony A100, A65, Nex5T, A7ii, A6500. 2 many lenses, mostly ordinary Minolta & 3rd party A, MC/D, other mf, vintage Vivitars & cats, LA-EA2,3,4 E16-50&55-210mm


Posted By: ABramley
Date Posted: 14 April 2008 at 13:48
Hi Shocaholica and Arkku.

I'm interested in following you lot into the realms of a chipped 58 1.2. I love mine in unchipped form, but chipped would be even better...

The chip's arrived from China, but I'm at a bit of a dilemma as to how to attach it. There just doesn't seem to be that much to put it on - I've seen your photos and it just seems to be floating! Although Shercando did cut out a chunk of the mount to fit it in. Here's some shots of mine:

Here's a mount - from a Dynax 7. Am I correct in saying that it's the 5 pins to the right that need contact, not to the left?



Here's a couple of where the rear of my 58 lines up with the mount - this is using Peter Ganzel's adaptor:





(Yes, needs a clean!)

And here's the front then rear of the chip:





Seeing as mine's from China, I thought I'd put it on top of my Chinese revision - bonus points to anyone who gets the subtle message :p

So what did you guys use to attach the chip? A bit of glue?

Thanks for all help!


Posted By: Arkku
Date Posted: 14 April 2008 at 14:57
Originally posted by ABramley ABramley wrote:

The chip's arrived from China, but I'm at a bit of a dilemma as to how to attach it. There just doesn't seem to be that much to put it on - I've seen your photos and it just seems to be floating!


Mine's attached with a bit of superglue under both ends of the long strip and some blu-tack padding under the chip itself (not really necessary, but I used that to hold it while finding the correct position).

I don't know about the Ganzel adapter if that's what you're using as I'm using an M42 to Minolta AF adapter for the mount (you could've bought that from James Lao with the chip already attached, by-the-way, which is probably the easiest and best solution to get the electrified conversion done). On many (but not all) M42 adapters there's a ridge suitably placed for the contact pads to rest upon, and you just need to make a little hole on the side for the wider part with the chip.

http://www.flickr.com/photos/arkku/2250355687/">

(I know the mount I have on there looks a bit mauled, but it's been through several insane DIY projects before this as its final resting place. And it works great. =)


Posted By: ABramley
Date Posted: 14 April 2008 at 23:19
Hi Arkku, thanks for that description - it's helpful.

Can I be really cheeky and ask if you could supply a closeup picture of the chip and its mounting?

What I'm thinking of doing is cutting the notch in the flange like you've done, and driving pins through the metal to form a shelf to rest the chip on - giving support.

Cheers!


Posted By: Shaocaholica
Date Posted: 15 April 2008 at 09:03
ABramley, did you happen to see my full build gallery I linked in the first post of this thread?

http://shaozhang.smugmug.com/gallery/4630693_jPsbU - Here it is again . Hopefully, that should answer all your questions about how I did mine. Since you have Pete's mount, the process should be exactly the same if you want to go my route.


Posted By: ABramley
Date Posted: 15 April 2008 at 13:31
Shaocahoolica - that's absolutely perfect. I'm sure I'll be able to follow that - I'll get back to you with the results!

Cheers :)


Posted By: trygve
Date Posted: 27 September 2008 at 11:56
Hello all.
I just recieved a copy of this lens in MD mount. IS there someone out there willing to convert it for me?? For a fee orcourse. I'd love to get a chipped version for it, so I can have focus confirmation and SSS...
Please PM me if you can help me in any way..


Posted By: Grubeater
Date Posted: 27 September 2008 at 14:31
A question for those who did the conversion themselves: What's easier, converting a lens to A-mount and chip it or cleaning the aperture blades of an AF lens?
Just curious, yesterday I cleaned the aperture blades of my 50mm F/1.4 again, last time was a year ago.

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Missing hood or other weird Minolta stuff? PM me. Maybe I can help.


Posted By: ricardovaste
Date Posted: 27 September 2008 at 14:34
Originally posted by Grubeater Grubeater wrote:

A question for those who did the conversion themselves: What's easier, converting a lens to A-mount and chip it or cleaning the aperture blades of an AF lens?
Just curious, yesterday I cleaned the aperture blades of my 50mm F/1.4 again, last time was a year ago.


Converting a lens. If the blades are really messy and the lube from the focus has gone everywhere, that can get pretty messy and you have to take it all apart and remove each blade and then put them back in...

A simple conversion like this can be done in half an hour or so with no extreme deconstruction.

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I photograph the moments in people's lives that mean the most to them: http://www.rharris-images.com/ - Richard Harris Photography


Posted By: Arkku
Date Posted: 27 September 2008 at 14:42
Originally posted by Grubeater Grubeater wrote:

A question for those who did the conversion themselves: What's easier, converting a lens to A-mount and chip it or cleaning the aperture blades of an AF lens?


Converting the lens. When I did my http://www.dyxum.com/dforum/forum_posts.asp?TID=19601 - conversion , it took about 45 minutes from obtaining the lens in the mail, without instructions or prior experience with said lens. It's very straightforward: unscrew old mount, drill holes in new mount, attach it (may require a bit of sanding, but it doesn't require any considerable accuracy). Adjusting infinity focus can be fiddly and takes most of the time, but again that's just turning a screw and/or installing spacers cut from aluminium baking foil. =)

Meanwhile, I find some of the AF lenses are a pain to dis- and reassemble correctly, especially ones that require that this be done from both directions to clean both sides of the aperture blades (though I find it is often possible to cheat and get good results by just cleaning one side).


Posted By: Grubeater
Date Posted: 27 September 2008 at 14:42
Cleaning the aperture blades of a 50/1.4 can also be done in half an hour, the only difficult part is putting the diaphragm assembly back in the right place. That task alone cost me half an hour yesterday, http://www.dyxum.com/dforum/forum_posts.asp?TID=17944&KW=blades&PID=173079#173079 - last year I hit the mark in one attempt, completing the cleaning in 30 minutes.

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Missing hood or other weird Minolta stuff? PM me. Maybe I can help.


Posted By: ricardovaste
Date Posted: 27 September 2008 at 14:45
Regardless of time, there is no extreme descontruction, you are just removing the rear mount.

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I photograph the moments in people's lives that mean the most to them: http://www.rharris-images.com/ - Richard Harris Photography


Posted By: 1969ho
Date Posted: 15 November 2008 at 21:02
From a modding rookie, a little clarification if possible before I travel down this road...

If I am interpreting all of that various posts here and elsewhere I've seen about modding a Minolta f1.2 58mm correctly, if I convert it using a chipped m42 mount (presumably a JamesLaoT single mode f1.1/60mm model), do I essentially end up with a lens that will work with my K/M D5 just like any other AF lens except for no auto-focus? Should all of the exposure modes work like normal or am I missing something?

Do I also understand that it wouldn't be quite the same if similar mods were done to a zoom/variable-f-stop lens (and that is where the multi-mode chips come into play)?

Thanks in advance,
Al


Posted By: Arkku
Date Posted: 16 November 2008 at 00:34
Originally posted by 1969ho 1969ho wrote:

If I am interpreting all of that various posts here and elsewhere I've seen about modding a Minolta f1.2 58mm correctly, if I convert it using a chipped m42 mount (presumably a JamesLaoT single mode f1.1/60mm model), do I essentially end up with a lens that will work with my K/M D5 just like any other AF lens except for no auto-focus? Should all of the exposure modes work like normal or am I missing something?


Only M and A modes will work, because the aperture control is manual as well. Also, the aperture selected in-camera only affects metering, not the aperture on the lens. This means that for using the exposure meter you must set the in-camera aperture wide open all the time and meter stopped down. (Or, alternatively, if the widest aperture programmed in the adapter matches that of the lens exposure compensation, you could meter wide open by setting the aperture in-camera, and then use exposure lock before stopping down. But this can lead to problems with the mechanical aperture actuator getting stuck, so not recommended.)


As for the conversion, I used the 60mm f/1.1 chip kindly provided by JamesLaoT, and installed it on a non-chipped M42 adapter I already had. If you don't already have the adapter, you can certainly use the chipped one directly. I believe some other chipped conversions, such as those featured in this thread, don't use an M42 adapter for parts, however, instead relying on custom-machined replacement mounts. (Personally I prefer the adapter-style conversion for various reasons.)


Posted By: 1969ho
Date Posted: 25 November 2008 at 02:42
Originally posted by Arkku Arkku wrote:

Originally posted by 1969ho 1969ho wrote:

If I am interpreting all of that various posts here and elsewhere I've seen about modding a Minolta f1.2 58mm correctly, if I convert it using a chipped m42 mount (presumably a JamesLaoT single mode f1.1/60mm model), do I essentially end up with a lens that will work with my K/M D5 just like any other AF lens except for no auto-focus? Should all of the exposure modes work like normal or am I missing something?


Only M and A modes will work, because the aperture control is manual as well. Also, the aperture selected in-camera only affects metering, not the aperture on the lens. This means that for using the exposure meter you must set the in-camera aperture wide open all the time and meter stopped down. (Or, alternatively, if the widest aperture programmed in the adapter matches that of the lens exposure compensation, you could meter wide open by setting the aperture in-camera, and then use exposure lock before stopping down. But this can lead to problems with the mechanical aperture actuator getting stuck, so not recommended.)


As for the conversion, I used the 60mm f/1.1 chip kindly provided by JamesLaoT, and installed it on a non-chipped M42 adapter I already had. If you don't already have the adapter, you can certainly use the chipped one directly. I believe some other chipped conversions, such as those featured in this thread, don't use an M42 adapter for parts, however, instead relying on custom-machined replacement mounts. (Personally I prefer the adapter-style conversion for various reasons.)


Thank you for the update. I just picked up a lens, so it's time for a little modding...

Not having had a MC/MD lens in years, I don't have one to look at until my 58mm arrives. Do you think there is any possibility of leaving in/modding the aperture link to allow 'S' mode to work as well? Is it
"just" an alignment issue with the AF mount, or is it just impossible do to a number of issues? I think I remember my old XE-7 having A, S, and Auto modes with the MD lenses I had back then.


Posted By: 1969ho
Date Posted: 16 December 2008 at 05:54
I have received and modded my 58mm f1.2. In addition to using a JamesLaoT adapter as a starting point, and this and other guides as a road map, I believe I have gone one step further than any of the mods I have seen posted on the net thus far.

I retained the internal aperture link ring and modified it to have an external tab corresponding to the correct AF location through the adapter. This allows me to start by manually set the F-stop to my desired setting, but the lens stays wide open during focusing and only stops down automatically for the photo or if I hit the depth-of-field-preview button on my KM-5D.

I haven't really had a chance to take any serious sample photos yet, and I may need a little bit of additional infinity focus adjusting, but so far so good.

Any interest in the details???


Posted By: Gabriel
Date Posted: 16 December 2008 at 09:01
But then you have to use AEL for correct metering, don't you?

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Pic a day http://tinyurl.com/2008-p-a-d - 2008 / http://tinyurl.com/2009-pad - 2009 / http://gabriel.mp3-tech.org/pics/galleries/2010_pic_a_day - 2010 galleries


Posted By: JamesLaoT
Date Posted: 16 December 2008 at 13:58
Originally posted by 1969ho 1969ho wrote:

I have received and modded my 58mm f1.2. In addition to using a JamesLaoT adapter as a starting point, and this and other guides as a road map, I believe I have gone one step further than any of the mods I have seen posted on the net thus far.

I retained the internal aperture link ring and modified it to have an external tab corresponding to the correct AF location through the adapter. This allows me to start by manually set the F-stop to my desired setting, but the lens stays wide open during focusing and only stops down automatically for the photo or if I hit the depth-of-field-preview button on my KM-5D.

I haven't really had a chance to take any serious sample photos yet, and I may need a little bit of additional infinity focus adjusting, but so far so good.

Any interest in the details???

Nice idea. It's worth a try.
If you can make the aperture ring have same angular rotation as the AF lens's. You can gain real AE function.
The MD/MC lens have less angular rotation then AF lens. So if you just link the aperture with body. you can gain limited AE,maybe get right metering when aperture below F8. In the other word, you can gain AE in a limited aperture range.

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http://eadpt.com/eadpen.htm - http://eadpt.com

M42 adapter with Focus Confirmation



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