Use of the Peak BG Blue Filter for Critical Focuser when you want to obtain more correct enlarging for the black and white film, use the focuser after fitting the BG filter to its eyepiece.
The use of this filter will permit the coincidence between the wavelength sensitive to your eyes and that to be enlarged.
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Comments about Peak Blue Filter for Critical Focuser (Replacement):
Fits on my Peak II. My focus has improved but to be fair the density of the filter is a small drawback and therefore requires concentrated effort to focus.
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