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  1. #11
    Mick Fagan's Avatar
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    Well another evening in the darkroom, another interesting development with the BG filter.

    My second set of eyes was unable to turn up, so the experiment I was envisaging, didn't happen. Instead I enlarged two negs for two prints.

    I'm using 35mm and 12x16" paper. One neg is full frame on the paper, and approximately 11 times enlargement. The other is a cropped print with the enlargement approximately 15 times.

    The most amazing thing is the 15 times enlargement, it is pin sharp, and that is an understatement! Mind you the other smaller enlargement is also pin sharp.

    I cannot wait until I have another set of eyes to back up my findings.

    Regardless of that, I am reasonably sure that using the BG filter with the peak focusing unit, in my darkroom, with my methods, is giving me more accurately focused B&W prints, than I have been able to do since I don't know when.

    I will post more results, when I'm able to get another set of eyes to confirm my findings.

    Mick.

  2. #12

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    Mick. I have read G Nocon's book and seen the print which he says proves the point about the filter. Maybe it's just my eyes or the book's reproduction but with due consideration now I really don't think I could see any difference. At the time and because Gene had said which was the sharper, I was looking for the difference and if pressed would have said that it was marginally sharper but I think this was due to conditioned thinking. I knew what I had to look for so I found it.

    Barry Thornton in his "Elements" book is quite unequivocal about claiming that this belief in the benefit of the blue filter is wrong and he goes into some detail as to why and says that in 25 out of 25 times a print focused through the blue filter then without brought the focusing knob to exactly the same marked position. In a blind test of prints both using the fliter and not, he and other viewers couldn't distinguish. Presumably he marked the backs and then shuffled the prints so neither he not his viewers knew which were which.

    Maybe you could try the Thornton focussing test and the blind print test and let us know if there was a difference that could not be accounted for by chance.

    I wonder if Gene Nocon's position remained the same? However it if works for you then that's all that counts.

    pentaxuser

  3. #13
    Mick Fagan's Avatar
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    Well some time has passed and I took great care with some enlargements doing prints with and without the BG filter on the Peak Focuser.

    When I am doing prints in my darkroom with the BG filter attached to the Peak Focuser I am definitely getting pin sharp prints.

    The time arrived when I had another set of eyes in the darkroom. My student came for another session. She developed her 35mm film, then made contacts. A negative was picked out for enlarging, test print done, some adjustments made; she nailed it on the second print. She also made positive comments about the Peak Focuser.

    I then asked her to humour me by using something different for focusing. I attached the BG filter and asked her to check the focus, adjust if necessary, but ensure that it was as good as she could get.

    Nothing else had changed, the neg had not been touched, the negative stage movement remained locked, the only change made was the lens was moved up and down slightly whilst attaining critical focus. This was then locked and another piece of paper was exposed.

    When we had dried the print and put it alongside the first print her first comment was, “How much does one of those Peak Focuser things cost?”

    In short, there was a real and quite significant difference in the BG filter print.

    Sharp is not correct, pin sharp is what came to mind.

    We brought the prints into the house for the missus to decide. There was no problem as whilst the first white light focused print looked very good, the BG focused print was outstanding. Razer sharp comes to mind.

    Now I have had a bit of time to reflect upon the apparent mystery of why some people say the BG filter works, whilst most say it doesn’t.

    I think that the changes made to the focusing part of an enlarger are so minute, that it is possible that only very well manufactured enlargers are capable of effecting these changes, and, more importantly, able to hold and lock the change in position.

    I would consider the LPL 7700 enlarger with the fine focus accessory a possible contender for this type of accuracy, as long as the negative stage was tightened up enough to eliminate any sag, once final focus has been attained or set.

    I did not measure the movement of the lens, the lens stage, or anything else on my enlarger. All my student and I did was to carefully focus the grain with the aid of a BG filter attached (crudely) to a Peak Focuser, nothing more, nothing less.

    Enlarger used: DeVere 4x5 free standing with drop table and single globe colour head

    2.8 50 Componon S lens.

    Ilford MGIV RC paper

    Film Neopan 400 35mm all cases.

    Negatives from two cameras and two photographers, with each photographer enlarging their own negative(s)

    I would be extremely interested to hear from anyone else who has one of these Peak Focusers with the BG filter and has tried the filter.

    If anyone in the Melbourne area wishes to come to my darkroom to see and try this, you're most welcome. The way I see it, the more minds able to see this and work out the pros and cons, the better.

    Mick.

  4. #14
    Jerevan's Avatar
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    It's an interesting thread, and I've followed it along, trawled the net a bit for information, but I can't figure one little detail... the "BG" part.

    Is it a shorthand for blue-green or is the filter of some other colour?
    “Do your work, then step back. The only path to serenity.” - Lao Tzu

  5. #15
    Mick Fagan's Avatar
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    Jerevan, it is a very dark blue filter which slips onto the rubber eyepiece. It doesn't slip on too easily either!

    http://www.peakoptics.com/product_in...products_id/62

    That is the manufacturer's own site explaining the filter. I don't know what the G stands for, it could be Blue Green, I just don't know.

    I do know though, I'm a bit excited at the way my printing has been transformed by the addition of this piece of equipment to my darkroom. However one does really need to have an enlarger capable of the minute adjustments one makes to ensure they are transposed to your print.

    Mick.

  6. #16

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    I think that this thread has done a fine job of showing that relying upon the statements of others that are well intended and that has been shown to be true in their own cases does not mean that you will not end up with different results from your own work.

    When I carefully and thoughtfully make tests and I end up being perfectly satisfied to believe my own eyes but hopefully I do not disparage what others have found to work for them. It is also true I believe to retest my assumptions every once in awhile to make sure I still are use what will work best for me.

    Good thread Mike! I am glad those lovely Australian snakes did not get you.
    Claire (Ms Anne Thrope is in the darkroom)

  7. #17
    Mick Fagan's Avatar
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    Jereven, I have been doing a bit of trawling for information about this BG filter. I found this piece of information on one of APUG's members site.

    "Variable contrast papers (VC) are coated with a mixture of separate emulsions. All components of the mixed emulsion are sensitive to blue light but vary in sensitivity to green light. Exposure to blue light produces a high contrast image, and exposure to green light produces a low contrast image. By varying the proportion of blue green light exposure, any intermediate paper contrast can be achieved."

    Source:- Calibration of dichroic heads to ISO paper grades, by Ralf W. Lambrecht


    Using the above information, one logically comes to the conclusion that the Peak manufacturing company calls the BG filter so, because it is used to focus light in the blue green part of the spectrum.

    I would be quite interested to know anyone else's explanation.

    Pity you don't live on the same continent, you could drop in and test it out yourself.

    For what it's worth, my student, after seeing how well the Peak Focuser worked on my enlarger, is now going to test it on her LPL 7700 enlarger, if the outcome is the same, she is going to purchase a Peak Focuser with the BG filter, the difference is that good.

    Mick.

  8. #18

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    B/G filter..

    Given that some posters have difficulty in finding any difference with this filter,I occurs to me that it may be a result of variations in colour perception in the eye (a.k.a "colour blindness).
    This is a surprisingly common condition,and,unless profound,most people will never notice a slight deficiency in colour vision. I find a benefit in using the filter,but my colour perception has been tested by my optometrist.
    I also use a common or garden Paterson grain focuser, so I would suggest you don't really need a Peak model.

  9. #19
    Mick Fagan's Avatar
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    Smudger, that is very interesting news, do you have a source or name, of the actual filter that you use?

    Until very recently I was also using the Paterson el-cheapo grain finder. If this can be converted to the accuracy of the very much more expensive Peak Focuser fitted with the BG filter, then the darkroom for some people could be made much better.

    What differences have you noticed?

    Mick.

  10. #20

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    Quote Originally Posted by Mick Fagan View Post
    ... if the outcome is the same, she is going to
    purchase a Peak Focuser with the BG filter, the
    difference is that good. Mick.
    Your lens is not well color corrected. Your student's
    lens may be more or less well color corrected. If her
    lens brings to the exact same focus all wave lengths
    from deep blue through red then her white image
    focus will be the exact same as seen using the
    BG filter. The better the print's sharpness
    with the BG the worse is the lens' color
    correction.

    BUT, your's and your students lenses may be Damn
    Good at producing a blue only image. Switch to blue
    sensitive only Graded paper and have your self prints
    sharper than pin sharp.

    More than one have posted, better to set the BG aside.
    They can say that because of the more precise color
    correction of their lenses.

    There are several fine points relating to focus and
    and filtering such as UV and violet sensitivity, filtering
    for, and other matters. I've Ctein's article on the
    subject but should review. I've a suspect lens
    myself that needs evaluation. Dan

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