Focus Frustrations and Max Print Size

[yeknom02]

I know I'm asking a lot of enlarging questions on this forum, but I guess there's no other way to learn in this day and age. So, please bear with me as I ask another one...

So, I have a Beseler 23C (the old blue industrial-style enlarger) and I just replaced the (very crappy) Beslar 50mm lens with a Nikkor f/2.8 N 50mm lens. The good news is that now my images are a lot sharper!

However, it seems like my maximum print size is only going to be an 8x10. This is because when I lift the enlarger head higher to make, say an 11x14 or a cropped 8x10, the image goes out of focus... I'm turning the focus knob and it's hitting its limit, bringing the lensboard as close to the condenser head as it can go. So, I swapped the 50mm and the 75mm Beslar I have. Why, you ask? Because the 75mm was mounted in a lens board that had a bit of a counterbore in it, which would (apparently) put it another millimeter or two closer to where it needs to be for correct focusing. It was only a slight improvement, if any.

So, my questions are: (1) Is this normal? (2) Do I need to start shopping for some sort of recessed lensboard for my new lens? (3) Why did I not have this problem with my Beslar lens if it was the same focal length?

 

[MattKing]

Do you have the condensor stage set to the right position?

Otherwise I would wonder if the lens stage has been modified in some way.

 

[walbergb]

Is the lamp house positioned to the match your film format? For example, if you are enlarging 35mm, then the lamp house should be cranked all the way up.

 

[yeknom02]

Yes, the lamp house is set to the 35mm mark (at the top of its range).

 

[Bob-D659]

Is the bellows fully compressed? Is there some sort of spacer installed to hold the negative carrier higher than it should be?

Here is a link to a manual for what looks like a pretty old model. Dead Link Removed

 

[yeknom02]

Yep, that's the model I have! It's a beauty in person. The lower bellows (the one between the lens and the negative stage) is indeed fully compressed. And my model looks exactly like the picture (except that it's blue), so I'm pretty sure there's no spacer installed.

 

[tleirtro]

I don't have this enlarger myself, but the lensboard for 50mm lenses on my Durst is indented. And I see a passage on page 9 in the manual above about inverting the lensboard for short focal lenses. Have you tried this?

Thor Egil

 

[Bob Carnie]

Check the play in the bellows when fully compressed, sometimes on my enlargers we have to tighten to get the bellows from slipping, if it is loose and all things are in the right position, you will have a hell of a time getting your images in focus

Yep, that's the model I have! It's a beauty in person. The lower bellows (the one between the lens and the negative stage) is indeed fully compressed. And my model looks exactly like the picture (except that it's blue), so I'm pretty sure there's no spacer installed.

 

[yeknom02]

Well, there's no "play" in the bellows, but I can keep rotating the focus knob after it's hit the fully-compressed limit. I'm guessing this is normal and that it's some sort of friction-based adjustment control, rather than a gear like the enlarger level is. Also, another good indicator is that once I set the focus, it won't shift as I let go of the knob, since I've even done this through the focus scope.

 

[Bob Carnie]

On my enlarger the bellows slip only happens when it is fully extended up for 35mm.

Well, there's no "play" in the bellows, but I can keep rotating the focus knob after it's hit the fully-compressed limit. I'm guessing this is normal and that it's some sort of friction-based adjustment control, rather than a gear like the enlarger level is. Also, another good indicator is that once I set the focus, it won't shift as I let go of the knob, since I've even done this through the focus scope.

 

[Ian C]

Beseler 23C Notes

From your comments, you have the standard column Beseler 23C. The maximum print size with a 50mm lens and a 35mm negative is 15” x 22 3/8” (The diameter of the largest focused image on the baseboard is 375mm). This is just barely possible with no cropping.

That translates into a 16X magnification and requires the center of the lens to be positioned about 53.13 mm from the negative.

For an 11” x 14” print with, say, 1/4" of the image overlapping the top and bottom of the print you need a 15.5X magnification with the center of the lens 53.2 mm from the negative. If something prevents attaining this dimension, then focusing won’t be possible.

Focusing the image is strictly due to the position of the lens relative to the negative and is independent of any condenser adjustments.

From you comments in post #9, I suspect that the friction drive for the focus might need to be tighter to allow the drive to compress the bellows slightly more. You might try to contact the maker to ask about adjusting the friction drive for the focusing.

http://www.beselerphoto.com/

With the standard-column 23C, if you use a 40mm wide-angle lens designed for 35mm enlarging you can make a 16” x 20” borderless print even using a 1” tall easel. Two good lenses for this are the 6-element 40mm f/4 EL Nikkor or the similar 40mm f/4 Rodagon WA.

Of course, you must get the lens even closer to the negative to attain focus. For that you need to mount the lens on a recessed lens board #8022. This board is also useful for making large horizontal projections with a 50 mm lens because the lens must be brought closer than usual to attain very large magnifications.

If you choose to buy a used board, be careful. There are a few old 42mm boards still out there. Sometimes eBay sellers are unaware of the difference. If you try to mount a 39mm lens on a 42mm board the tightening force generated by the retaining ring can break the bottom edge of the plastic barrel of the newer N version EL Nikkor. This happens because the metal shoulder of the lens falls into the hole so that the tightening force is applied to the plastic barrel instead of the metal shoulder.

You can find useful information on the Beseler 23C here:

http://www.oresteen.com/bess23c.htm

 

[yeknom02]

Ian, thanks for the explanations. I have the blue 23C Series II that you see in the third picture on the second link you posted.

Reading over your comments, I wonder if the problem is due to the fact that (I think) the Nikkor lens is taller than the Beslar it has replaced. That is, the height dimension of the lens assembly is greater, meaning that the "center of the lens" (if I understand the terminology correctly) is therefore shifted downward, away from the condenser head and closer to the baseboard.

Since I unfortunately don't have access to my enlarger except on select days, I'll have to check the friction drive when I can - are there telltale signs I can look for that would indicate it needs adjustment?

In the meantime, I'll look for a #8022 lens board. It sounds like if I can't solve my compression problem, then a recessed lens board could be a workaround.

 

[Ian C]

The fact that the focus knob rotates without closing the bellows sufficiently to focus an 11” x 14” print (which is within the range of the 23C with 35mm negative and 50mm lens) is a giveaway that the mechanism is slipping too easily.

Some owners get carried away with lubrication. It might be possible that there is oil between the driving parts. There ought to be no oil between a drive wheel and its driven shaft. I’ve not had mine apart, so I’m uncertain of the construction.

If it is a drive wheel in contact with a shaft, then oil between them could result in slipping as the resistance of the bellows starting to compress opposes the movement.

There’s a sheet metal cover at the rear of the focus mechanism that can be pried off to expose the parts. If they’re oily, you could remove excess oil with mineral spirits on a small rag. If oily parts are the problem, then removing the oil may restore normal operation without further adjustment.

It might be best to try to get the information on cleaning and adjusting the mechanism from Beseler before proceeding.

 

[Bob-D659]

It's not so much the Nikkor is taller, a lot of lenses have the rear element well past the end of the 39mm threaded mount, like Componon's. That few millimeters can make all the difference.

 

[yeknom02]

It's not so much the Nikkor is taller, a lot of lenses have the rear element well past the end of the 39mm threaded mount, like Componon's. That few millimeters can make all the difference.

Well, the Nikkor is (if I remember correctly) taller, but the rear element is still flush with the lens board. So, the midpoint of the height (or centroid, if you wish) is therefore shifted away from the lamp head, which might be important and might call for a recessed board. Or, perhaps my friction drive needs adjusting as Ian suggests. Hopefully I can get in touch with someone at Beseler. (fingers crossed)

 

[MattKing]

Is there any chance that the bellows between the negative stage and the lens stage isn't the original one and is incorrect?

 

[yeknom02]

I checked the enlarger today. The bellows is not the limiting factor, nor is the friction drive of the focus control. The lens stage is able to be raised (and is able to stay) all the way up to the negative stage. Looking at the rear reveals that the two are in contact, except for two very thin washers, which are there for protection (and they don't look like they were added after production.)

 

[ic-racer]

You need a recessed lensboard.

 

[PVia]

For an 11” x 14” print with, say, 1/4" of the image overlapping the top and bottom of the print you need a 15.5X magnification with the center of the lens 53.2 mm from the negative.

I think you mean centimeters...

 

[archer]

I agree with ic-racer, you definitely need a recessed lens board with the El Nikkor 50 f2.
Denise Libby

 

[darinwc]

Out of curiosity, are you currently using a flat lensboard or does it have a 'cone" extention on it?

I think everyone is assuming you are allready using the flat.. but you know what they say about assumptions.

 

[lem3]

I have a blue 23C and Nikkor 1:2.8 and have no difficulty focusing 11x14 images. The label on the box reads "#8023 Lensboard with Pilot Light for El Nikkor and Componar 3.5 Lenses".

 

[yeknom02]

I've come up with two conclusions:

1 - There's no reason why I shouldn't be able to focus with my standard lens board. I must be a millimeter or two off for whatever reason.
2 - A recessed lens board is an acceptable solution - I installed the lens on an 8022 board and I achieved focus even at maximum height.