Beseler Dichro 45S vignetting

[false_Aesthetic]

Hey,


I have a student that really wants to print 4x5--the first time in the 3 years I've been at my job. The only problem is that we have Beseler Dichro 45S heads which, as I recall, vignette something gross.

Is there a (relatively simple) hack to fix this?

[banjo]

#1 what lens are you trying to use
#2 the head needs to be all the way down as close to the Neg. carrer as it can
#3 you need the 4x5 Mixing Chamber

[false_Aesthetic]

1) 150mm Nikkor somethin or other
2) done.
3) done.

[banjo]

what kind of lens board Flat or tude

[neil poulsen]

I'm not sure what you mean by vignetting. Do you mean that the image gets lighter towards the corners and edges?

Or, does the image lose sharpness towards the corners and edges?

[false_Aesthetic]

sorry, the image gets lighter towards the edges. I guess that's not exactly vignetting but its the word that popped in my head.

The lens is on a flat lens board.

[frotog]

Unless you have that head mounted on a cb-7 chassis, you will experience some vignetting with a beseler enlarger and 4x5 neg. due to the gap between the source and the negative. On my 45mxt chassis I was able to lessen this effect by removing some material around the flange that the source sits in, effectively bringing the source closer to the neg. Hope this helps.

[Greg Blank]

You should provide more details.

I have the 45S (Is a dichroic Diffused Light source ) on a MXT chassis. With Schnieder 150 & 135mm stopped up or down I have never seen this issue. I use a standard glassless carrier. My enlarger required alignment by me once in 20 plus years.

1) So is the carrier a standard or do you have a glass carrier?

The 45S allows different mixing chambers, are you positive the 4x5 chamber is installed?

Have you looked at the students negatives to make sure that this is not being produced by the camera. If its possible to swap the lens try a newer or other brand.

The top portion of the bellows should be flat as others state, the bottom section should be drawn (extended) approximately the focal length of the lens.

sorry, the image gets lighter towards the edges. I guess that's not exactly vignetting but its the word that popped in my head.

The lens is on a flat lens board.

[tgtaylor]

Unless you have that head mounted on a cb-7 chassis, you will experience some vignetting with a beseler enlarger and 4x5 neg. due to the gap between the source and the negative. On my 45mxt chassis I was able to lessen this effect by removing some material around the flange that the source sits in, effectively bringing the source closer to the neg. Hope this helps.

I have the 45S head mounted on an MXT and have never experienced vignetting or even drop-off using lens from 50mm to 180mm. Perhaps your head is not seated correctly. There are twin bars on either side of the of the top bellows specificially for seating and locking down the head. Unloosen the lock-down screws and make sure the head is seated correctly between the bars and then tighten them down. A torpedo level placed on top of the head will then show that it is level. If it doesn't, well then you have a bent chassis or something.

Also, check that both negative and lens stage are correctly aligned. I use a laser alignment tool for this and routinely check alignment at the beginning of every printing session. It only takes a minute.

Thomas

Thomas

[Gem Singer]

"Corners are light".

Sounds like the wrong size mixing chamber in the dichro head.