Home
SearchSearch MemberlistMemberlist RegisterRegister ProfileProfile Log in to check your private messagesLog in to check your private messages Log inLog in

Minolta Rokkor 28mm 2,5 SI
View previous topic :: View next topic  


PostPosted: Mon Aug 26, 2019 11:55 am    Post subject: Minolta Rokkor 28mm 2,5 SI Reply with quote

This is a fantastic lens.

[url]Les jeunes de la Défense by lumens pixel, sur Flickr[/url]


PostPosted: Tue Aug 27, 2019 8:45 pm    Post subject: Reply with quote

It is a very under rated lens, one of my best 28's, costs 1/5 of what my next best 28mm lens.


PostPosted: Tue Aug 27, 2019 9:28 pm    Post subject: Reply with quote

Great image, and a great lens as well. Like 1 small


PostPosted: Wed Aug 28, 2019 1:43 am    Post subject: Reply with quote

Yes, the 28mm 2.5 returns a lot of quality for relatively little$$. Nice lens and nice pic there. Best, jt


PostPosted: Wed Aug 28, 2019 7:04 pm    Post subject: Reply with quote

This lens spent three months under an Ikea lamp to cure yellowing. Well worth this little effort.


PostPosted: Thu Aug 29, 2019 3:12 pm    Post subject: Reply with quote

There doesn’t seem to be much info out there about this lens. Do you have anymore sample pictures?


PostPosted: Thu Aug 29, 2019 5:17 pm    Post subject: Reply with quote

Some info here:

http://forum.mflenses.com/all-eight-minolta-28mm-rokkor-computations-compared-t77162,highlight,%2Bminolta+%2Brokkor+%2B28mm+%2B2+%2B5.html

My copy of the 2,5 after curing yellowing seems better than what i see there.


PostPosted: Thu Aug 29, 2019 5:23 pm    Post subject: Reply with quote

Some pics:

[url][/url]Printemps by lumens pixel, sur Flickr[/url]


And these last two fully opened:

[url][/url]Tunnel by lumens pixel, sur Flickr[/url]

[url][/url]Dans la boîte | In the box by lumens pixel, sur Flickr[/url]


PostPosted: Thu Aug 29, 2019 7:00 pm    Post subject: Reply with quote

Thank you. I just picked one up. It was pretty cheap so worth trying.
The flower picture seems to have a good amount of CA though.


PostPosted: Thu Aug 29, 2019 8:12 pm    Post subject: Reply with quote

Glad you bought one.

I do not see any fringing. By the way these flowers were not purely white Laughing


PostPosted: Fri Aug 30, 2019 12:49 am    Post subject: Reply with quote

I don't see any CA in the flower picture.


PostPosted: Sat Aug 31, 2019 3:38 am    Post subject: Reply with quote

Did you have to deyellow yours? If so, then how did you deyellow it?


PostPosted: Fri Sep 06, 2019 10:27 pm    Post subject: Reply with quote

Updating this for others just in case they come upon this thread in the future.
De-yellowing this lens is super simple. I have a small UV led flashlight that I use to hunt scorpions.
The flashlight has a flat surface that rests perfectly on the metal around the rear element without touching the glass.
I put a down a piece of aluminum foil, put the front of the lens down on the foil then put the flashlight on the metal around the rear element.
A couple of hours and the yellow cast is gone. No disassembly required. Please let me know if pictures would help.

I bought my flashlight long ago, so not this one, but looks exactly like this light:

https://www.amazon.com/Flashlight-Portable-Ultraviolet-Detector-Batteries/dp/B00GU55270/ref=sr_1_7?keywords=uv+flash&qid=1567808180&s=sporting-goods&sr=1-7

I tried to use the same method with my Carl Zeiss Jena Pancolar 50 f/1.8.
On that lens this had no effect. That Zeiss is as yellow as it started and I have had that UV light on there for days.
Not sure what I am going to do about that lens.


PostPosted: Fri Sep 06, 2019 10:52 pm    Post subject: Reply with quote

cbass wrote:
Updating this for others just in case they come upon this thread in the future.
De-yellowing this lens is super simple. I have a small UV led flashlight that I use to hunt scorpions.
The flashlight has a flat surface that rests perfectly on the metal around the rear element without touching the glass.
I put a down a piece of aluminum foil, put the front of the lens down on the foil then put the flashlight on the metal around the rear element.
A couple of hours and the yellow cast is gone. No disassembly required. Please let me know if pictures would help.

I bought my flashlight long ago, so not this one, but looks exactly like this light:

https://www.amazon.com/Flashlight-Portable-Ultraviolet-Detector-Batteries/dp/B00GU55270/ref=sr_1_7?keywords=uv+flash&qid=1567808180&s=sporting-goods&sr=1-7

I tried to use the same method with my Carl Zeiss Jena Pancolar 50 f/1.8.
On that lens this had no effect. That Zeiss is as yellow as it started and I have had that UV light on there for days.
Not sure what I am going to do about that lens.


3 weeks of LED from an IKEA (Jansjö) helped on mine.


PostPosted: Sat Sep 07, 2019 1:00 am    Post subject: Reply with quote

Ikea lamp on a pancolar?


PostPosted: Sat Sep 07, 2019 10:00 pm    Post subject: Reply with quote

Yes, I can post results in a new thread.

#1


PostPosted: Fri Sep 13, 2019 1:44 am    Post subject: Reply with quote

Thank you for the info. I am trying that on my Pancolar right now.


PostPosted: Fri Sep 13, 2019 4:53 am    Post subject: Reply with quote

I have had good luck with a cheap LED UV light bulb used for indoor plants. I just put it in a normal light fixture a little above the lens I was treating. I used it it to de yellow a Minolta 28mm 2.5 and 58mm 1.2 in just a couple days, the extra power probably helped to speed it up.


PostPosted: Fri Sep 13, 2019 10:05 am    Post subject: Reply with quote

Do 'em in bulk! Wink

I got this UV lightbox at a radio ham fair, apparently it was used to cure electronic components encased in resin Question whatever....it only cost me £5 and works just fine.