Peak BG filter for B&W enlarging

Smudger · Nov 5, 2006

B/G filter..

Mick - to answer your earlier question : The filter I used was cut from a Rosco swatch book : "daylight" Tough TD25 "Converts 3200K to 6000 K ".
Hardly scientific ,in fact I'm of a mind to experiment with a variety of blue filters.
I'll post my impressions.
FWIW : all my lenses are EL Nikkors : 63mm/80mm/105mm/150mm , which are,according to Nikon "corrected for the near ultraviolet range,to which most black & white enlarging papers are sensitive".

MattKing · Nov 5, 2006

I wonder, what would the effect be of focussing with full cyan filtration dialled in on my dichroic head?

or,

What would the effect be of focussing with full cyan and full magenta filtration dialled in on my dichroic head?

Matt

dancqu · Nov 6, 2006

Smudger said:
..."daylight" Tough TD25 "Converts 3200K to 6000 K ".
I'm of a mind to experiment with a variety of blue filters.

EL Nikkors : 63mm/80mm/105mm/150mm , which are,
according to Nikon "corrected for the near ultraviolet
range,to which most black & white enlarging
papers are sensitive".

Blue filters for viewing?
I've a 105mm Nikkor to check. I'd take
that Nikon quote to mean that the Nikkors are
corrected THROUGH the near ultraviolet. If those
very short and not so short wave lengths do coverage
with all those longer wave lengths of the visible spectrum,
then the BG or other deep blue will make no improvement
in the focus. Dan

gamincurieux · Nov 28, 2010

I've bought a Peak scope, but without any blue filter that I could see. I only read now after the fact about the blue filter.

I'm wondering (without yet having a darkroom session to try it) if I could just put a normal camera lens Blue filter (Nikon B12 or B+W KB12, both of which I happen to have in my drawer here) over the Peak scope eyepiece to get the same effect when focusing a black & white neg????

ic-racer · Nov 28, 2010

I just got a second Peak 1 new in box, but it did not come with the plastic eyepiece lens cap. However, I found a good use for the included blue fiter---it acts as a good lencap for the eyepiece

gamincurieux · Nov 29, 2010

It's a Peak 3, by the way.

gamincurieux said:
I've bought a Peak scope, but without any blue filter that I could see. I only read now after the fact about the blue filter.

I'm wondering (without yet having a darkroom session to try it) if I could just put a normal camera lens Blue filter (Nikon B12 or B+W KB12, both of which I happen to have in my drawer here) over the Peak scope eyepiece to get the same effect when focusing a black & white neg????

gamincurieux · Dec 5, 2010

Bump...

Quote Originally Posted by gamincurieux View Post
I've bought a Peak scope, but without any blue filter that I could see. I only read now after the fact about the blue filter.

I'm wondering (without yet having a darkroom session to try it) if I could just put a normal camera lens Blue filter (Nikon B12 or B+W KB12, both of which I happen to have in my drawer here) over the Peak scope eyepiece to get the same effect when focusing a black & white neg????

ic-racer · Dec 5, 2010

You may not need the filter. It is to help your eye focus on the little box. The human eye focuses red and blue on different planes. Cutting the red may help you see the box better. Other than that it produces no effect on the rays coming from the enlarger lens.

naaldvoerder · Dec 6, 2010

Ralph Lambrecht and Chris Woodhouse in "Way Beyond Monochrome" seem to find no improvement of sharpness using the bluefilter.

emerson531 · Jun 20, 2020

Mick Fagan said:
Dan, that is a point I had not considered, makes good sense. I will borrow a friend's Apo enlarging lens and see how that goes.

I have been producing exceptionally sharp colour RA4 and EP2 prints from negatives, for around 20 years with this lens.

I was of the understanding that this lens was, or should be alright for B&W. It could be though, that it has limitations with the latest VC papers.

I have produced quite stunning pictures over 15 years ago with this same lens, but that was single B&W graded paper.

I am learning a lot from this thread, makes life interesting, eh?

Mick.

Mick Fagan · Jun 21, 2020

Emerson, been a long interval between contributions to this thread.

Some answers.

My student tried out my Peak grain focuser on her LPL 7700 enlarger and could not repeat the slight focusing changes that made quite dramatic focusing changes to prints. It was this that made us conclude that many of the people who have used the BG filter on their Peak units, were unable to fine focus exactly enough to make a difference. The main reason this appears to be so, is probably due to the mechanical construction of their enlargers.

As mentioned previously, I have a De Vere 504 free standing enlarger. These enlargers would have to be very close to perfection in aligning the negative stage with the lens stage and the easel stage. Not to mention the extremely accurate focusing stage with it's locking mechanism fitted to this enlarger. I know of no other enlarger with the accuracy of the De Vere units.

As for borrowing an Apochromatic enlarging lens, which I did mention. That never eventuated, there is only so much sharpness one can endure.

I still use the BG filter, although sparingly as it does take time and in general if I'm making smallish prints, then the effort is not worth it. That said, when I do make prints that are going up on walls, then I use the BG filter and I can still see the difference. However as my eyesight has slowly gotten worse with age, using the BG filter has become harder to accurately use. I have found that younger people with their far better eyesight, can still produce sharper prints with my enlarger and the use of the BG filter. By younger, I mean under 40 years of age.

Mick.

DREW WILEY · Jun 24, 2020

Peak magnifiers once came standard with a deep blue filter. That was relative to not only when papers were primarily graded and blue-sensitive, but when most conventional enlarging lenses weren't necessarily well corrected. A true apo enlarging lens won't exhibit any focus shift relative to color. I say "true" apo because that implies something more strictly defined than just an apo marketing tweak. For very critical work I use Apo Nikkor "process" lenses, which are even better corrected than "apo" enlarging lenses. Obviously everything has to be perfectly in plane to do any kind of accurate focus. The film HAS to be held truly flat in a serious glass carrier. And no cheapo filter material can be introduced in the optical path itself or all of this fuss
becomes meaningless (I noticed one one of the ancient posts that someone tried a piece of Rosco lighting gel). I have quite a collection of enlarging lenses, both conventional and cannibalized from the graphics industry. All are relatively modern (post-60's).There isn't a single one of them, with the exception of a relatively cheap 75mm, which exhibits any focus shift. And even the cheapo 75 is consistent just one stop down from wide open. Of course, all enlarging lenses need to be stopped down slightly for ideal performance. Let me also state that not all grain magnifiers are created equal. I use a Peak Critical model with the tilting mirror - the gold standard. I've seen some cheap products that were next to worthless.

Peak BG filter for B&W enlarging

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