Levelling problem

[Shiny]

the only way i can get 6x4.5 negatives sharp across the whole negative is to tilt the enlarger head so that its no where even close to parallel with the baseboard, giving a warped print. The lens is in the head correctly and not stuck in at an angle.

Could there be an element in the lens (75mm E Rokkor) that is out? I have never noticed this problem with 35mm negatives and a 50mm rokkor.

Thanks

Jim

 

[galyons]

Does this problem occur on all MF negs? Glass or glassless negative carrier? Glassless can let the neg "pop" creating focussing issues. Does stopping down help? Try the 75mm with a 35mm neg. It is unlikely to be the lens, but this would provide a cross check. These are factors to check first.
Cheers,
Geary

the only way i can get 6x4.5 negatives sharp across the whole negative is to tilt the enlarger head so that its no where even close to parallel with the baseboard, giving a warped print. The lens is in the head correctly and not stuck in at an angle.

Could there be an element in the lens (75mm E Rokkor) that is out? I have never noticed this problem with 35mm negatives and a 50mm rokkor.

Thanks

Jim

 

[wilsonneal]

I have a similar mystery with my D2. I bought the Omega leveling tool, and the baseboard and neg stage are perfectly aligned, and the neg looks square on the easel, but it's not sharp edge to edge.

Neal

 

[grahamp]

If the baseboard and the negative stage are parallel planes, then you have three other variables:

The lens axis must be perpendicular to the negative plane. You can get errors here if the lens is held with a retaining ring and not a threaded mount, or you cross-threaded the mount. If you are swapping lenses on lensboards, the board itself could be warped or failing to engage in the chassis correctly.

The lens could have a displaced element. I would be surprised that you could correct for that with a simple tilt of the head.

A displaced condenser or mirror can have some odd effects. Usually just illumination issues though.

 

[grahamp]

One other point (I hate following up on my own posts) - make test prints on each size using the 'wrong' lens. The 75mm should be fine for the 35mm frame, though the 50mm will be stretched on the 645. It should be good enough to see if the problem is the format or the lens/mount.

 

[Donald Miller]

Check your easel. I once had an easel that was out of level.

 

[grahamp]

Now there's a thought. And the 50mm would give a little more depth than the 75mm at a given aperture and mask the effect.

 

[Shiny]

Thanks, im checking everything i can. The image is perfectly square on the baseboard, it looks a lot better with the 50mm lens, but that doesn't cover the whole neg. I may try a cheap 80mm just to see if its the lens. The mount looks fine - condenser etc all level.

Its a glassless negative carrier (durst F60) but im fairly certain i've got the negative dead flat. To get the image sharp edge to edge i would have to raise the right side of the easel by more than an inch which seems a lot.

I may just have to stop right down for the time being.

Thanks

jim

 

[Neal]

Dear Jim,

I don't know what sort of enlarger you have, but on my Omega you must also align the lens to the baseboard.

Neal Wydra

 

[dancqu]

...but im fairly certain i've got the negative dead flat. jim

I've aligned my Omega B8 using a surface of the
negative carrier. IIRC the top surface. No negative.

The B8, a 6x9 D2, has both lens and negative stage
provisions for alignment. IIRC, I first squared the
projected outline of the negative carrier then
began a lengthy balancing of adjustments
of negative and lens stages.

There are alignment tools of the point to point
type. They may or may not affix to a surface
which represents the actual film surface.

The proof of perfect or near so alignment is
the projected image. Dan

 

[wilsonneal]

Dear Jim,

I don't know what sort of enlarger you have, but on my Omega you must also align the lens to the baseboard.

Neal Wydra

Yeah, I cannot figure out how to do that on my D2. Doesn't seem to be any adjustments at the lens plane.

N

 

[Neal]

Dear N,

The entire carrier can be tilted fore and aft by rotating the axles of the rollers. They are offset drilled. Side to side adjustment can be made by sliding the lateral support bars that the brass bars of the focusing mechanism pass through. After that, the negative stage can be adjusted using the four screws holding it in place.

Now I will tell you my dirty little secret for adjusting the lens stage. I use shims under the main support. Much easier, particularly for side to side adjustments.

Neal Wydra

 

[Parsifal]

Can we assume you have used a level on baseboard and film plane? Is the lensboard screwed in tight in all cases? Can you borrow a 4x5 lens from someone else and substitute it for a print?

Sounds like a real potential can of worms. Good Luck!

 

[dancqu]

Can we assume you have used a level
on baseboard and film plane?

A level uses surfaces which themselves may be
imperfect planes. Both pressed steel or aluminum
at the film stage and warped base boards can give
false readings. Levels thenselves do not guarantee
level. I use the projected image of the negative
carrier itself. Dan

 

[glbeas]

Check out this thread from a while back.
(there was a url link here which no longer exists)
Note the mirror technique I use on mine, seems to work well for me. The other techniques discussed are equally good if done right.

 

[grahamp]

If it is a F60 then there are not many adjustment options - it is just an F30 on steroids. If the projected image is square (check by measuring the two diagonals), but one edge is unsharp, then the lens has to be displaced. I wonder if the lens extension mechanism (a solid sliding baffle unit, not bellows, on a couple of friction drive rods, I think) is binding and twisting the lens slightly at enlarging distances. If so, I would expect it to be worse at small enlargements. You should be able to go from postcard to 12x16 in with one of these without trouble.

If the lens is damaged I would be amazed if it was aligning to exactly a left-right error. You can check by unscrewing the lens a quarter turn (lock it up again afterwards!) and seeing if the sharpness location changes. If not, it has to be the chassis, and I'd look at the focus mechanism and 'bellows' first.

You might need to check that the 6x6 carrier springs (I think it is like the F30 in this respect) are equal strength, and that you are using it the right way up.

 

[Shiny]

looks like its the lens, unscrewing it changes the location of the un-sharp area. unscrewing a half turn changes the area of focus to exactly the other side.

i'll check again when i get home from christmas

thanks
jim

 

[dancqu]

If the projected image is square
(check by measuring the two diagonals)

You have in mind that if the two diagonals are of
equal length then the projected image is a rectangle.
The isosceles trapezoid also has diagonals of equal
length. None of it's angles are right angles.

I've not aligned my enlarger in the last few years.
It's such a damn frustrating job. Proof of alignment
is on the baseboard or easel. As with the first time
through, a square will be used.

I'm wondering if square alone meets ALL the
requirements. I seem to recall that forcus all four
corners needed attention and was coupled with
the squaring of the image. Frustrating. Dan