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PostPosted: Fri Sep 28, 2007 12:02 am    Post subject: Reply with quote

Perhaps I found out why some people have this infinity focus problem with the Zenitar and have to open the lens to "fix" that: I bet their lens lacks the rear filter. I have tried to remove the rear filter from my lens and the focusing goes out of whack - it does not focus farther than about 1 meter. With the filter on, the lens focuses correctly.

Rear filters are a valid point to buy the lens from a shop, as on Ebay you may get a copy where the filter is not present. There are four rear filters provided with the lens, one clear correction filter, that comes mounted on the lens, and three B&W coloured filters, provided in a separate box.


PostPosted: Fri Sep 28, 2007 7:16 am    Post subject: Reply with quote

Orio wrote:
Perhaps I found out why some people have this infinity focus problem with the Zenitar and have to open the lens to "fix" that: I bet their lens lacks the rear filter. I have tried to remove the rear filter from my lens and the focusing goes out of whack - it does not focus farther than about 1 meter. With the filter on, the lens focuses correctly.


That's right. There are, however, several texts in the internet that explain how important the filter is for the lens. So it shouldn't be a problem for somebody who can read and wants to learn.

But then, not all the people are as open to information as we are, right?
I mean, this forum shows that we want to learn and thus do not have such problems for long. We'll find a solution or get some help by other members. One more reason to like this place!


patrickh wrote:
"They pretend to pay us and we pretend to work"

Laughing Laughing


PostPosted: Fri Sep 28, 2007 7:24 am    Post subject: Reply with quote

peterqd wrote:
lahnet wrote:
You need to remove the pin (easy) to shoot at f2.8->.
http://www.dyxum.com/dforum/forum_posts.asp?TID=6375


Now things are back to normal I can correct this. There is no need to damage the lens by removing the pin. Just use a M42/EOS adapter with the flange that keeps the pin depressed. I think the idea of removing the pin (or jamming it) started because the flange-type adapter hadn't yet been thought of. BTW, the Helios 44-M4 works this way too.


Absolutely right. I use Sony/Minolta and this is not possible on "my platform". That is why we poor Sony users have to remove the pin.

Orio - The rear filter is not the problem for anyone else but a fool Very Happy Very Happy I hope you can se I mean it in a humours way Very Happy


Last edited by lahnet on Fri Sep 28, 2007 7:38 am; edited 1 time in total


PostPosted: Fri Sep 28, 2007 7:37 am    Post subject: Reply with quote

LucisPictor wrote:


That's right. There are, however, several texts in the internet that explain how important the filter is for the lens. So it shouldn't be a problem for somebody who can read and wants to learn.


The problem is that when you buy used, you don't always get the filters. I know for sure, because I asked about one Zenitar for sale, and the seller replied sorry no filters.

So it is important to remember this, perhaps one day we will make a "MFL Buyer's FAQ) and we will write in it "remember to check for the availability of rear filters for Zenitar and MIR-20"


PostPosted: Fri Sep 28, 2007 9:07 am    Post subject: Reply with quote

Comparing the Zenitar on 1.6x crop format and on full format:





They really act like two different lenses. On crop format, it becomes a moderate wideangle and the fish distortion is easily removed with PT Lens; on full frame, the fisheye distortion is much bigger and not easily removable with PT Lens alone, at least I'm not able to, I need to also use Photoshop's Distort tool.
BTW the black thing you see top right on the full frame image is not vignetting, it's the roof of my house!


PostPosted: Fri Sep 28, 2007 9:15 am    Post subject: Reply with quote

Orio wrote:
...So it is important to remember this, perhaps one day we will make a "MFL Buyer's FAQ) and we will write in it "remember to check for the availability of rear filters for Zenitar and MIR-20"


Yes, good idea! Indeed a very good idea! We definitely should do that!

Thanks for the pictures. The difference is obvious. That's why it works for me with my 350D. Wink


PostPosted: Fri Sep 28, 2007 9:20 am    Post subject: Reply with quote

The main problem with the full frame format, is that you also have significant horizontal distortion (like it's visible on the horizontal bar of the balcony fence), while with crop frame format the horizontal distortion is negligible, and this allows for easy correction in PTLens.

Of course this is a problem if you want a rectilinear final result. If you want a fisheye result it's no problem at all.