In my case, Omega DII with stock 4x5 condensers on 6x6 neg. Wrong condenser set for the neg. Way bigger, covers the neg with light but...
In the DII there are different lens cones that put the 135mm lens far away from the neg. The condenser set that works for a lens that has to be far away from the neg is not aimed right for an 80mm lens (on a flat board) that has to be really close to the neg.
When I lifted the head to remove the negative (another DII 'feature'), I could see the falloff go away. The light improved. I could have held the head up and gotten even lighting. That's how I immediately knew the falloff was due to the condensers. Fortunately I had the correct set of condensers so I just swapped them out and continued.
I could swear I use the 80mm for 6x9 all the time with no coverage issues. Have to check my notes. This time I needed the extra contrast, otherwise I usually use a fluorescent head where none of this stuff about condensers applies. (With a DII anyway, it is painful because they are not adjustable).
I'm trying to picture your scenario and just can't seem to get it to "work." If a lens' view covers the total negative, then the corners won't be vignetted as badly as the OP's as far as I can see, no matter what the magnification. That is, unless there is an illumination issue, or something is blocking the light path.
Yes, I agree with you, that there is a certain amount of falloff with most enlargers (the need for edge burning as SOP confirms this in most cases), and I agree that, if possible, the area of the negative that one wants to print (the cropped portion) should be as nearly centered in the lens' field of view as possible. But, even with falloff, the corners should not be totally white in the print (i.e., almost no light at all getting to the paper) unless there is a lens coverage issue.
IIRC, the OP stated that he/she cropped out the right hand corners, which also were vignetted. If that is the case, then indeed all four corners are vignetted, and that 75mm lens just won't cover 6x7. Or, he/she has one an illumination problem like I mentioned above.
I print with both Omega DIIs and Beseler 45ms, but with diffusion sources. With a lens that is adequate for the negative size I am printing, I just can't seem to imagine any way the corners of the negative would get vignetted as long as the light source covered the negative adequately... I can move the easel so that half the print is "in the dark" and the negative image still shows a the clean edge of the negative carrier. Corners are fine, even at high magnification. I can place all four corners in the middle of the print and they are clean and relatively well lit. Maybe it is a condenser issue/lens placement issue as Bill suggests, but once that is fixed, then there really should be no problems getting the corners to print as far as I can see as long as the lens coverage is adequate.
If I'm missing something here, maybe you could give me a more detailed explanation? TIA
Here is a quick 8x10 print of the full negative with the easel centered under the lens. I dont see any falloff at all with the 75mm Nikon.. Bob must be correct about the issue being from cropping the image by moving the easel. Last night i removed the condenser tube to look and see if something look out of wack and put it back in place this morning.. Could the condensers have been out of line and when i put them back they fell back into place? This is a bad image of the print sitting in the fixer taken with my cell phone. No burning or dodging was done, just a quick exposure.
Here is a tip.
I wish I could draw this but I can't so I will try to explain.
Every printing session we do this.
Example: 12x18 prints from 35mm negs= correct aspect ratio.
therefore we set the enlarger height to this size.
we set the easel blades to 12x18 full frame for this ratio of film
we place correct lens in holder ,
we set the condensers to the correct position.
we make sure the bulb is working.
We place a 35 negative carrier into place which is centered to the lens, condensor and bulb. we focus without a neg in place to see the outside edges of the neg carrier.( I tape with electrical tape the position on the 4x5 glass, I am not using a standard carrier and this may be where you are not seeing my workflow}
We then take the carrier out of the enlarger and project the light, we drop the bellows slightlyand therefore can see the condensor circles....
We then move the easel into position with the 4 corners of the blades touching the condesor circles.. this tells us we are exactly centered top to bottom.
We use Duct Tape,( because we love Red Green and are Canadians) and tape the easel into place.
We do not move the easel again for this printing session,,, If we need to crop we move the negative into place, remember I am using 4x5 glass carrier and can move the neg, it is not in a strip the negative is individually cut so we can do this.
I hope this makes sense. Moving the easel will cause some problems in some darkrooms, I have seen enough darkrooms to know this to be true.
When you do that, what do you do to take care of the possible flare caused by white light coming through outside of the 35mm neg frame? Do you mask it or just let it be? Is this a non-issue?
Develop, stop, fix.... wait.... where's my film?
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Yes I mask each holder .....with the black tape, I have a holder for each format.
Originally Posted by tkamiya
Here is a view of the back of my negative glass carriers , 35mm and 6x7
I use black electrical tape so this is the bottom facing the easel.
Bob and Cantore,
If the last photo of the OP's posted is the negative printed full-frame, then, obviously, I must be wrong. There is only slight falloff in the corners, which indicates that the lens is covering for the most part. (Although, I do see a slight clipping of the corners, it is not nearly as pronounced as in the first two images).
So, the fact that there was falloff at one point and much less now confuses me a bit. I can understand it if there were an illumination issue, i.e., condenser misalignment, something in the light path, etc. that caused the edge of the negative to be improperly illuminated, which was then corrected when the OP removed and replaced the condensers (or made some other adjustment).
I still fail to see, however, how you can get anything but a clean straight edge projected from the edges of the negative carrier unless there is a problem either with the lens coverage or the illumination. When things are set up correctly, there should be no such falloff as shown in the OP's original postings.
A thought experiment: I set up my enlarger to project a full-frame image slightly smaller than my 16x20 inch easel, so I can see the film rebate and the edges of the negative carrier projected on the enlarging surface. I then remove my 16x20 easel and get out my 8x10 easel. This I place on the baseboard so that one of the corners is centered on the enlarging surface. I am effectively cropping by moving the easel, and I am intentionally placing part of the photo paper "in the dark," i.e., outside the projected image. I make a print. I repeat this for the other three corners. As far as I can see, I should get no falloff at the corners other that that inherent in the optical system (i.e., the combination of falloff from the lens and slightly uneven enlarger illumination, which in my experience is 5-10% or so). I should have prints of the corners of my negative with the film rebate showing and nice clean lines from the edges of the negative carrier.
And Bob, don't misunderstand me, I really think your practice for cropping is best practice (I also center the area of the negative I am printing when cropping). And I understand your workflow completely. I just don't see how I can explain the OP's original problem by "cropping by moving the easel." I originally thought there was a coverage problem, now I'm leaning to misalignment of the light source somehow. Unless I'm really missing something here, if everything is aligned correctly, even with the slight falloff and the reduced lens performance at the corners of the image, there should be no problem getting a good image of edges and corners of prints. How could one print full-frame without the same problems?
Last edited by Doremus Scudder; 02-03-2012 at 04:50 AM. Click to view previous post history.
Your posts are starting to make me think i should print this negative again while cropping the image by moving the easel. I no longer feel comfortable thinking the moving of the easel was the issue because of the fact that i removed the condenser tube and replace it before i did the last test print. I will post the results a little later.
I did a final test and you were correct that moving the easel did not cause my issue! I framed the image by moving the easel and made sure that the edge of the negative was apx 1/2 inch from the blade and i got a straight line line you mentioned.. I'm very happy to lean that i dont have to center the easel under the lens, i have more options now on how i want to frame the print.. It was the condensers that caused the issue. Thanks!!