Sekor 250mm f8 (for Mamiya Press cameras) issue on infinity focus !

[DiogoB]

Early this year i bough a Mamiya Press Super 23 with the ground glass and 2 Sekor lenses, 100mm 3.5 and the 250mm f8 (250mm wich i found not so much information about in the web).
The 100mm is lovely, no problems at all. The 250mm got me bad results all of my photos were out of focus, but scince this lens has no communication with the range finder and to be fair zone focus it's not my best skill, i assumed that it was a skill issue at my end...
Well, today i just went out with this lens and with the ground glass just to try nailing the focus, but for my surprise this lens could not focus at infinity (the lens is in a fantastic condition, looks pretty new with evidence of low use).
I'm kind of lost here, i'm not used to tele lenses, but as far as i know this is not related with the lack of extension tubes, i need to pull the lens closer to the film to focus at infinity (correct me if i'm wrong) not pushing it away from the film. So i'm missing something here ?
Do you think that my lens it's broken even with no substancial use ? i know it could be dropped and not dented so...
Hope someone has this same set up and could bring some light !

 

[MARTIE]

The instruction manual says something about the 250mm f5 EXCLUSIVELY FOR THE SUPER 23.
Could it be that your f8 is for a different model of Mamiya Press camera, such as the Universal?

 

[thinkbrown]

The instruction manual says something about the 250mm f5 EXCLUSIVELY FOR THE SUPER 23.
Could it be that your f8 is for a different model of Mamiya Press camera, such as the Universal?

The 250mm f5 is for the super 23 and later. the "exclusively for the super 23" bit is because for some reason it's incompatible with the original press. the 250mm f8 should be compatible with all press bodies afaik, though I personally own the f5.

 

[thinkbrown]

I'd start with checking the basics. Are the front and rear element groups both installed within the lens securely? Did you accidentally extend the bellows slightly while attaching the ground glass?

It's definitely confusing because frankly there's not *that* much to go wrong with a press, especially since you're not relying on rangefinder coupling.

 

[reddesert]

The 250mm f5 is for the super 23 and later. the "exclusively for the super 23" bit is because for some reason it's incompatible with the original press. the 250mm f8 should be compatible with all press bodies afaik, though I personally own the f5.

The 250 f/5 is limited to the Super 23 and later because it's too heavy/big for the lens mount of the original Press 23/Standard 23 cameras (on early bodies the lens rotates to mount, vs the breechlock in the later cameras). All the other lenses are supposed to be compatible with all the bodies.

I have never had either the 250/5 or the 250/8, so I don't know what is wrong with the lens, but like others said there are some things you should check:
- Check the ground glass back and position, does the other lens/lenses focus correctly at infinity on the ground glass, agreeing with the RF and the lens focus scale?
- Are the front and back lens cells of the 250 securely screwed into the lens/shutter?
- Can you focus on some closer object and get a sharply focused image across the frame?

 

[Focomatter]

My 250/8 focuses just fine near infinity (~ 200m) as it is very foggy today. Just checked it on a chrome Universal with a ground glass back using a Toyo loupe borrowed from my 8x10 bag.

 

[DiogoB]

I'd start with checking the basics. Are the front and rear element groups both installed within the lens securely? Did you accidentally extend the bellows slightly while attaching the ground glass?

It's definitely confusing because frankly there's not *that* much to go wrong with a press, especially since you're not relying on rangefinder coupling.

The 250 f/5 is limited to the Super 23 and later because it's too heavy/big for the lens mount of the original Press 23/Standard 23 cameras (on early bodies the lens rotates to mount, vs the breechlock in the later cameras). All the other lenses are supposed to be compatible with all the bodies.

I have never had either the 250/5 or the 250/8, so I don't know what is wrong with the lens, but like others said there are some things you should check:
- Check the ground glass back and position, does the other lens/lenses focus correctly at infinity on the ground glass, agreeing with the RF and the lens focus scale?
- Are the front and back lens cells of the 250 securely screwed into the lens/shutter?
- Can you focus on some closer object and get a sharply focused image across the frame?

Well the front element easily gets off when unscrewed, and it's pretty tight at this point, so i believe it's good ! The rear element it's tight as well, but i cant seem to get it off (i dont have the right tools for it at my disposal to try to turn it, but it's tight i cannot turn it by hand, and looks "normal").
The bellows are locked in the closest position (pushed as far as it goes against the camera body).
And yes, the 100mm focus at infinity looking trough the ground glass.
About the focus at other ranges, it looks focused at subjects that are near, like 5 meters... Honestly f8 with the ground glass it's a though set up to check critical focus, the image it's really dim, so tomorrow (it's night time atm here) ill check if the focus is linear across the frame at closer distances, it looked focus at close distances but i cannot be sure if it's across the whole frame frame.

 

[DiogoB]

My 250/8 focuses just fine near infinity (~ 200m) as it is very foggy today. Just checked it on a chrome Universal with a ground glass back using a Toyo loupe borrowed from my 8x10 bag.

Well, so this is what i was afraid. You have the same lens and it's working as expected ! I'm using a Super 23 but as far as i know it should work the same way... I know there are a few differences like you can use a Graflok/Graflex adaptor a polaroid back and i cannot. Universal doesnt has the bellows and such... But i believe it should work in the same way with this lens !

 

[Focomatter]

Well, so this is what i was afraid. You have the same lens and it's working as expected ! I'm using a Super 23 but as far as i know it should work the same way... I know there are a few differences like you can use a Graflok/Graflex adaptor a polaroid back and i cannot. Universal doesnt has the bellows and such... But i believe it should work in the same way with this lens !

In fact that is what I was using, the baby Graphic style back with a ground glass. The Universal does not have the Linhof Technika style back extender thingies. Make sure these are retracted on your Super - they are for camera movements and for extra focus extension so not good for infinity except the Tessar type 100mm used in retracted position.