Vacuum easels....necessary????

There seems to be a consensus of opinion that glass negative carriers

contribute to sharper projected images on the paper by keeping the

film in plane. I have noticed quite a few vacuum easels for sale of

late. Now in theory they sound good and would help in the overall

alignment of the enlarger system by keeping the paper in plane. I

have noticed while using conventional easels that the paper was not

flat across its entire surface, and although the prints appeared to

be sharp I felt they could be better( 4x5 up to 11x14). Barry

Thornton in his interesting book "Edge of Darkness" on pages 139

&140, raises and lowers the easel 16mm above and below the focus

point on the paper and the prints are still sharp at these distances.

Now 16mm, which as im sure you know is over 1/2 inch..Do any of you

think this may be a typo? Has anyone noticed any benifit from using

one compared to a conventional easel,other than a vertical

arrangement.

 

Thanks

Regards, Richard

Richard, I can see the advantages of a vacuum easel if I were using a horizontal enlarger,or projecting onto a roll of 40" wide mural paper, but thats about it(pure personal opinion!) as far as keeping paper on a plane parallel with the negative, it would also depend on if the table you're vacuum easel sat on was also on a parallel plane. Certainly not an issue to loose sleep over, though the thought of converting an Argyle, Nuarc or Clyesdale into a LF enlarger would be fun if you've got the real estate!

I have a 30x40 vacuum easel. I used to have a smaller one that I

made myself. I can remember a few times when it failed to work

properly and the paper curled causing the image to soften in

those areas. It was noticeable. I was using a 150mm lens.

 

Here is my guess. Enlarger lens are just like regular lenses, The

longer the focal length the shallower the DOF. Clearly, a 50mm

lens is more tolerant of error than a 210mm enlarger lens

because its DOF at say f8 is much greater.

 

I also remember an article I read many years ago about image

sharpness Essentially what they did was focus a 35mm camera

on a coin in the distance. They then made a series of exposures

starting at f2.8, f4 f5.6, f8, f11, f16, and f22. For each exposure, an

extreme enlargement was made so the coin filled and 8x10 print.

In each print the coin was the same size. The lens they used

was an f1.8 50mm lens. As the aperture was reduced in size you

could see the sharpness of the coin diminish. There was a big

difference between f2.8 and f22. I guess at f22 diffraction took its

toll.

 

Why Thornton noticed no differences and I did may have to do

with the focal length of his enlarger lens, the f-stop used, and the

degree of enlargement.

 

My belief is that image sharpness or lack of sharpness is

dependent on many variables. There is:

 

1. The field lens

 

2. The camera support

 

3. The shutter release

 

4. The rigidity of the camera

 

5. The alignment of the film plane with the ground glass

 

6. The flatness of the film in the cut film holder

 

7. The type of film used

 

8. The alignment of the three enlarger planes

 

9. The flatness of the film in the negative holder

 

10. The regidity of the enlarger column

 

11. The enlarger lens

 

12. The smoothness of the paper surface

 

13. The flatness of paper (vacuum easel).

 

Each by itself, if managed optimally, contributes little. But,

collectively, these variables do degraded the sharpness of

image. In my quest to make big clear images I leave nothing to

chance. I try for optimal solutions for each of these variables

including using a vacuum easel.

 

I hope this helps.

As above John stated, vertical positioning and all that, I agree but stopping

down to f16 when printing pretty much works all the bugs out if your enlarger

is aligned properly.

Vacuum easels are a very nice thing to have if one ever goes to any process that requires contact printing. This would be Azo, Salt, Carbon, Pt-pd, Albumen, cyanotypes among others. These processes are enjoying a resurgence in popularity.

Thanks for all the response...Barry Thornton auther of the "Edge of Darkness" emailed that paper flatness is not an issue unless your making very large enlargements. Also a downside to vacuum easels is the vibration from the vac. pump degrading the image.

 

Regards, Richard

In graphics arts usage; and process cameras; the paper must be flat. This is because we are reproducing maps and drawings. A curved up paper edge results in a scale error on a map; or a border that is drunk; ie not straight. All can be in focus; bit the print will be amiss; with a drunk edge; or a line that is not straight. Also the print wont fit the customers frame; if the paper edges cause a difference in actual print size. It seems the concern of this thread is only focus; instead of keeping ones paper flat for other reasons. My comments are from using 42" wide rolls of paper.<BR><BR>In vertical vacuum frames; the vacuum avoids the usage of masking tape on the paper; which can tear the paper; and ruin a giant poster.<BR><BR>A proper vacuum frame adds no unsharpness to a print. Somebody must have not set up their darkroom properly; or have a really bad enlarger. The blowers on ours are far away from the frames; and add no unsharpness.