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Minolta 800mm f/8 mirror lens?
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PostPosted: Sat Sep 04, 2010 5:01 pm    Post subject: Reply with quote
Fretless Pete wrote:
Ok, thanks for that. I thought when Sony took over everything that all Minolta lens from whatever period would fit


Nope. Minolta changed their lens mount with the introduction of the Maxxum 7000 back in the mid-80s. Funny how they've never encountered the level of flack from that move that Canon has.

Here's a discussion where folks claim to have made the conversion to Sony Alpha, although no how-to:

http://www.dyxum.com/dforum/minolta-md-135-f28_topic58012.html

Here's a blog article where the guy gives his email address toward the end, inviting folks to contact him if they have questions about converting the mount:

http://alphamaxxum.blogspot.com/2008/10/mdmc-lenses-for-your-alpha.html

At last! A guy posted a how-to with pics up at Flickr:

http://www.flickr.com/photos/arkku/1266937278/in/set-72157600018767343/


PostPosted: Sat Sep 04, 2010 5:17 pm    Post subject: Reply with quote
motleypixel wrote:
LOL, have a look at this one:
Click here to see on Ebay

-Roy

Roy, please can you use the Ebay tags for linking to auction items, not the full link. The continuous text in links scrolls off the edge of the screen instead of wrapping. I've changed this one for you, all you need to do is put the ebay item number between the ebay tags.

Many thanks


PostPosted: Sat Sep 04, 2010 9:52 pm    Post subject: Reply with quote
Interesting reading Michael thanks for those links


PostPosted: Sun Sep 05, 2010 12:05 am    Post subject: Reply with quote
Peter, sorry about that...I should have known...I can do bbc tags about as fast as the shortcuts...don't see many ebay tags on forums.

Yes good reading on the Minolta conversions...I'm in the midtst of converting several Rokkor-X primes by machining both the MD mount w/aperture mechanics and M42-EOS adapters.

Here's how I achieved infinity focus on a 58/1.4:

http://vimeo.com/13115731

800/8 is still in its case...I have shop upgrades in-progress right now and won't get to serious tinker-time for at least a few weeks.

-Roy


PostPosted: Mon Sep 27, 2010 2:14 pm    Post subject: Reply with quote
Well the conversion of this lens to Canon EOS is done (non-destructive, i.e. easily reverted back to original Minolta SR mount).

Here's a quick video I did of the moon close to the horizon last night: http://vimeo.com/15313629

More to come with pictures of the lens/video of the conversion/sample stills.

-Roy


PostPosted: Mon Sep 27, 2010 2:49 pm    Post subject: Reply with quote
Ouststanding, Roy.

*Idea!* Now what you need to do is cobble together an adapter so you can mount a telescope eyepiece focuser, and then you'll have yourself a decent little planetary telescope.


PostPosted: Mon Sep 27, 2010 8:21 pm    Post subject: Reply with quote
Thanks Michael. I just finished up doing some serious shots from the 6th floor of our office here in Austin. We are sitting up on a 1000' elevation ridge to begin with and up until a year ago we were the tallest office building in the area. On a tripod, MLU, at ~ 1/200th sec. and 5X LV zoom focus, this thing is stellar! It's funny...a car that is approximately 300 yards away, LV 10X is TOO CLOSE to focus so I have to back off to 5X LV focus Smile

So in this mount conversion I simply removed the original RS mount (which has a 39mm screw in filter that says "Minolta Normal") and it's just a clear piece of glass, really no optical value in my eyes. I've seen other 800/8 Rokkors and they have like 4 types (colored, ND, and clear/UV) that screw into the mount. PLUS, it has a another rear drop-in filter from the side that says Minolta No. 8 and again...what the heck is it used for?

So for now as a Canon mount I only have the drop in filter. The screw in 39mm is left behind in the orig. removed RS mount. I already know a way to use a 42/39 female bushing to make it such that my machined M42-EOS adapter can receive the 39mm screw in filter, but is it worth the trouble? I figure the best it can do is keep the dust out of the back of the lens.

To me, having both the drop-in and screw-in filter removed would make for the best IQ.

-Roy


PostPosted: Tue Sep 28, 2010 2:03 am    Post subject: Reply with quote
Welp, I've read on occasion that some of these long lenses with optical flats in their light path actually need them in there for best performance. Just what I've read, but it bears passing it on. You might want to do some digging -- seek out others who have that lens maybe? -- and see what they have to say about the use of these add-ins.


PostPosted: Tue Sep 28, 2010 4:19 pm    Post subject: Reply with quote
cooltouch wrote:
Welp, I've read on occasion that some of these long lenses with optical flats in their light path actually need them in there for best performance.


So have I. I think it was some 300/2.8 lens I read about, which had more CA and didn't reach infinity focus without the drop-in filter. I wouldn't simply assume that such a filter is there without a good reason.


PostPosted: Tue Sep 28, 2010 7:45 pm    Post subject: Reply with quote
AhamB wrote:
cooltouch wrote:
Welp, I've read on occasion that some of these long lenses with optical flats in their light path actually need them in there for best performance.


So have I. I think it was some 300/2.8 lens I read about, which had more CA and didn't reach infinity focus without the drop-in filter. I wouldn't simply assume that such a filter is there without a good reason.


Valid point and therefore I will machine receiving threads in the new mount to enable the use of both filters and then it's simply a matter of performing a controlled test without any filters, just the drop in, just the screw in, and finally both filters and compare.

-Roy


PostPosted: Wed Sep 29, 2010 12:49 pm    Post subject: Reply with quote
Another video which I think turned out a bit better: http://vimeo.com/15379986

Now, I am very anxious to put that screw in filter inside the machined M42-EOS adapter and I have a way that will work fairly easily. I really want to take still comparisons with and w/o these filters.

I borrowed a Canon 100-400 and used my 17-40 f/4L and took shots of the Austin skyline yesterday at 20mm, 40mm, 100mm, 200mm, 300mm, 400mm, and finally 800mm with this lens to show the focal length comparison. I have a good set of sample images as well. Working on a complete short video showing off this lens and should have it in a a week or so.

I also have two Minolta TC's 1.5X and 2X and I'm seriously considering converting the rear-end of one and mounting it to the stock Minolta RS mount on the 800/8 and see what I get.

-Roy
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