Using APO enlarger Lenses

[Dinesh]

Dear Graham,

There's also the 'Bullshit Baffles Brains' argument: there are always those who will set themselves up as authorities and give out ex cathedra advice which, unless challenged, might be taken as authoritative despite being partially misleading or indeed on occasion flatly wrong.
Cheers,

Roger

In other news, pot calls kettle black!

 

[Roger Hicks]

In other news, pot calls kettle black!

No. I am prepared to admit I'm wrong, when it happens -- and it does. I merely assume that anyone reading a debate has the intelligence to decide between two competing viewpoints, and also to decide that the truth may lie somewhere between the two. Generally, when a thread has gone on long enough, I reckon that the reader can decide who is more likely to be correct: who has resorted to ad hominem arguments, who has left questions unanswered. Note my observations about filters and focal length: I learned something.

Note also that I am the one who suggests that everyone should be aware of a 'Bullshit Baffles Brains' scenario, and that I do not exclude myself from the possibility of being so accused. I have in the past given advice that I now believe to be wrong, because I have since learned more. The most enthusiastic bullshit artists are those least willing to admit that they can be wrong, and least willing to learn. I know I can be wrong, and that I can learn. I think I've said as much, more than once, so I find your comment mildly offensive.

 

[Dave Miller]

Dear Graham,

There's also the 'Bullshit Baffles Brains' argument: there are always those who will set themselves up as authorities and give out ex cathedra advice which, unless challenged, might be taken as authoritative despite being partially misleading or indeed on occasion flatly wrong. This is not an especial reference to this thread, but a general observation.

Cheers,

Roger

That's what I meant by "Rubbish"; but Roger is so much more eloquent than I.

Graham,
I appreciate your circumstances, but how long would it take you to print the same image at each stop from wide open to minimum so that you can compare actual results for yourself? I suspect that unless they are big enlargements, you will be hard put to tell the difference between them. A good investment of your time and 6 sheets of paper?

 

[jd callow]

Dave,
Excellent point. It might be worthwhile to do a mag test. Set the enlarger head at its highest point you'd be likely to use and make a series of 8x10s (this may exceed the lens's stated performance range). I'd set the paper off of center so that you'll have an idea of how well it resolves outside of the center.

As Dave suggests the resolving power of the paper may not catch any differences between one aperture and the next at most enlargement sizes. You may notice a change in contrast.

 

[Ole]

My thinking is that an ad hominem attack is when you call someone a jerk?

That's my thinking too.

As I've stated before, my technical knowledge, my photography skills and my scanning skills are three completely different things.

I know a brilliant photographer who is not only technically just about incompetent (so he does everything exactly the same way - saves thinking), but also a complete asshole. Yet he takes wonderful pictures, and is considered one of the masters in his trade.

 

[GFDarlington]

Dave, JD et all

Thanks for your recent posts. Actually I'd already done this sort of testing earlier on the Thursday night before I posted my 'calm down plea'. I didn't magnify the image as suggested, or use six sheets of paper (well, I do live in Yorkshire!), or indeed, test all of the f stop settings, just f4, f11 and f22, all on borderless 16x12 RC paper.

Except for the f22 setting, which seems to have a slight mushiness/lack of crisp edge detail, and possibly a slight lack of contrast, particularly towards the edges of the print, I couldn't really discern too much difference between them. Certainly not enough between f4 and f11 at that size of enlargement to make an obvious difference to my naked eye.

Still, I'm glad I didn't carry out such a test right at the beginning. I might never have posted my question, and, as this was my first request for advice, I can honestly say that I now feel well and truly a part of the diverse and always entertaining APUG community.

Graham

 

[Ed Sukach]

Now that there has been a "cooling off" period, I will claim to have been successful in establishing my point: that there IS a system of establishing a "minimum acceptable aperture" with enlarging (and camera) lenses, and that the manufacturers are cognizant of this, and design their lenses appropriately.

Whether we accept the performance of their lenses or not is another question, involving perception, aesthetcs and many other factors. We are all entitled to make our own decisions - hopefully for "good reasons".

There has been much written here that I consider to be "off topic". In an effort to "right the ship", I've posted a few comments in the "Ethics and Philosophy" Forum. Hopefully, they are appropriate there - if not - I will suggest moving further discussion to the "Soapbox".

 

[Brook Hill]

Extra time for dodging

Would dialing in equal amounts of yellow, blue and magenta on the LPL C7700 have the effect of a neutral density filter? It would, of course, limit using the top and bottom grades on VC paper. I did hear that 30 of each equals about a stop.
Tony

 

[jd callow]

Would dialing in equal amounts of yellow, blue and magenta on the LPL C7700 have the effect of a neutral density filter? It would, of course, limit using the top and bottom grades on VC paper. I did hear that 30 of each equals about a stop.
Tony

yes if the blue is really cyan.

 

[Early Riser]

Would dialing in equal amounts of yellow, blue and magenta on the LPL C7700 have the effect of a neutral density filter? It would, of course, limit using the top and bottom grades on VC paper. I did hear that 30 of each equals about a stop.
Tony

Brook this is a technique I have used as well but stopped as it really does limit the amount of magenta and yellow available to you. Also I heard recently from a very highly regarded exhibition printer that he used Blue filtration, it might be in the form of a separate blue filter, to go beyond the magenta and grade 5 limit. I have yet to test this, but the source is pretty unimpeachable. This may create a further reason not to dial in cyan as ND as it may actually affect contrast settings.

 

[srs5694]

Would dialing in equal amounts of yellow, blue and magenta on the LPL C7700 have the effect of a neutral density filter? It would, of course, limit using the top and bottom grades on VC paper. I did hear that 30 of each equals about a stop.

In theory, yes, if by "blue" you mean "cyan." Note, however, that the cyan filtration should (again, theoretically) have no effect on B&W papers. Thus, you could omit that filtration, using only equal amounts of magenta and yellow, to produce a brighter image on the paper. (That might not be good for focusing, though, since it'll bias the image toward the red, and the human eye focuses best with white or green light.)

In practice, the filters might not be in spec, so this effect could cause a shift in the exposure and/or contrast of the print. If you start with a filtered light, though, this shouldn't really matter, since you'd then adjust from your starting point. This could have an effect if you made a print and then added the filtration to produce longer exposure times to do dodging and burning, say. If you intend to use filtration in this way, you could try doing some tests, varying filtration and f-stop or exposure time to see if you get reasonably consistent results.

 

[lee]

the blue filter (47b using Kodak's Wratten scale) is the color that Aristo uses with the two color head they make and sell. It will give the hardest filtration available with VC type papers. The Green 58 filter will give the softest. That is the basis for split grade printing with VC type papers. Currently I use filters that I purchased from Rosco Filters.

lee\c

 

[Early Riser]

the blue filter (47b using Kodak's Wratten scale) is the color that Aristo uses with the two color head they make and sell. It will give the hardest filtration available with VC type papers. The Green 58 filter will give the softest. That is the basis for split grade printing with VC type papers. Currently I use filters that I purchased from Rosco Filters.

lee\c

Lee, my color theory has gotten rusty but wouldn't adding cyan and magenta on a dichro head give you blue? I'm wondering now if I could use my minolta color meter, read a 47B, and then see what combo of Magenta and Cyan give me the same color temp, and hopefully spectral output as a 47b.

 

[srs5694]

wouldn't adding cyan and magenta on a dichro head give you blue?

Yes, but remember that B&W papers are insensitive to red light, and cyan is just white light minus red light. Therefore, adding cyan filtration has (theoretically) no effect on B&W printing; filtering cyan is removing light to which the paper is "blind" to begin with.

Of course, this is a sort of theoretical ideal. In practice a paper might have some small sensitivity to red light or the cyan filter might block a small amount of green and/or blue light. Also, in reality color is a continuum; the red/green/blue distinction is somewhat arbitrary, although it's a convenient one for many photographic purposes.

As a practical matter, I routinely turn off the red light on my Philips PCS150 light source when printing in B&W. (The Philips uses an unusual three-color light source, with individually-dimmable red, green, and blue lights rather than cyan, magenta, and yellow filters.) I did some casual tests and couldn't tell the difference between prints made this way and prints made with the red light shining. My turning off the red light is theoretically equivalent to turning up the cyan filtration all the way on a conventional color head, but I can't think of any practical advantage of doing so on such a head. On my enlarger, turning off the red bulb extends its life.

 

[lee]

Early Riser I dont know the answer to that question. I am using a Durst 138s condenser model and just use the green and blue filters.

lee\c