Vignetting in one corner

[optique]

When I attempt to enlarge a 4x5 negative full frame to 8x10 paper, I get one corner (only) vignetted.

This is my first attempt with a 4x5 negative enlargement since I just got my lens!

I am using a 45MXT enlarger with a 135mm Componon. After removing the carrier, the enlarger is adjusted so that the light circle is at its widest. The upper adjustment on the enlarger (sorry, don't know the real name) is at the lowest position. I have experimented with the adjustment up and down.

It is kind of hard to tell, but it does seem like that the edge of the light circle is protruded upon by the edge of the projected image, thus causing the vignetting...

(In case it matters, I am not having this problem with my other lens (105mm and 6x7 negatives))

I know I can crop out the vignette, but what is the right way to fix or investigate this?


Thanks in advance.
Steve.

 

[Ian Grant]

It may be that you're not using the correct bulb, so it's not illuminating evenly.

Ian

 

[archphoto]

Take out the 4x5 inch negative carrier and see if your board is illuminated fully, if not it could be that the enlarging lens is not centred properly.

Peter

 

[optique]

Ian, this is the bulb (edit: ph212) I was told to buy. However, is that what people use for this enlarger?

Peter, If I measure to ensure that the lens is centered on the lens board, will that be good enough? I guess I should ensure that the board is seated right in the enlarger also.

Something else I forgot to mention. I am using a glass carrier but with only one of the glasses, since one was broken when I bought it. The fact that only one edge is vignetted would seem to mean that the carrier itself is not an issue, right?

Thanks very much. You guys are great.
Steve.

 

[archphoto]

Q: is everything lined up propperly and otherwise try turning the lamp in little steps if that can be done.

 

[Konical]

Good Morning, Steve,

The 212 is the correct bulb.

I use the same combination of lens and enlarger. The 135 componon works perfectly well for me, but it doesn't have much excess coverage with 4 x 5 film. It's hard to tell what your problem may be, but I'd double-check the centering of the lens and the carrier position in the enlarger.

Konical

 

[JRJacobs]

It is a good possibility that your enlarger is out of alignment.

 

[ic-racer]

If it is only one corner, then things are not lined up correctly. The light source needs to be centered over the negative carrier. The lens then needs to be centered to those two.

A lot of different ways to center things. You could trace out your projected image of the light source onto some paper. Then put the negative carrier in and make sure the projected image of the carrier opening is centered in you circle you drew. I usually measure from corner to corner to get it perfectly in the center. Then I trace out the projected negative carrier image and make an 'x' from corner to corner. From the center of the 'x' I point the laser alignment device at the front element of the lens and make sure the reflected diffraction pattern is centered. On my Omega, there is enough side to side play in the light box and negative carrier to get everything lined up with the lens perfectly.

 

[Andrew Moxom]

The upper adjustment must be a close as possible to get the lens coverage you need .... bellows of this stage need to be closed right up closer to the light source. The neg carrier should have pins to get it registered correctly. The focusing should be easy after that.

 

[optique]

Nothing is ever easy, is it?

When I get home, I will take another look. In the mean time, thanks for everyone's help.
Steve.

 

[optique]

Solved: Vignette in One corner Only

To make a long story short, my above lens (drawer) filter holder (makeshift cardboard) was obscuring the light. What threw me was it worked for 6x7 but did not work for 4x5. Removing the filter completely solves the problem.

I have not enlarged the negative again but based on looking at the projected image circle, my 135mm Componon S should cover 4x5.

Of course, now I have to mess with making 4x5 adequate holders for my 6x6 Ilford filters which should be no issue.

My hard look at the dissasembled enlarger optical parts showed quite a bit of dust on the glass surfaces, and even a fair amount of dust on the front and back sides of the lens.

I appreciate the responses.
Steve.

 

[ic-racer]

(makeshift cardboard) was obscuring the light.

Nice to see you got it figured out. Looks like it will be a straight-forward solution.