Minolta 300 f4 HS filter - question

[bonneville]

I have had my Min 300 f4 HS for a while now and although I haven't used it much, I am very pleased with it. It has a filter tray that slides neatly into the barrel of the lens and mine has a 42mm Minolta AC Normal filter screwed into it.

I lifted this from "camerafilters.com":

Achromatic (AC) Lens
A new multicoated filter that features color-corrected, 2-element construction. Designed especially for use in combination with zoom lenses having a standard focal range. Recommended for use on 35mm SLR cameras. All require no exposure compensation.

Does it have any effect on a digital? If I remove it would it make a difference?

Is there a range of other filters for this lens?

Thanks, in anticipation.

[David Kilpatrick]

Confusing! The quote refers to a Minolta Achromatic Close Up Lens, which is entirely different from a Minolta Achromatic Coated filter - though the abbreviation AC applies to both. An AC close-up lens is a cemented doublet (two glass elements) with a positive value, like a weak magnifying glass, that you can screw on to the front of your tele or zoom to get closer focus. The AC filter is a filter coated to prevent reflections.

Minolta invented Achromatic coating in the late 1950s. It consisted of using different thicknesses of deposited mineral coating on the glass, so that there was no colour shift caused (regular single-layer coatings always alter the colour transmission). In the 1960s, they introduced Double Achromatic Coating, the first type of multicoating, in which two layers of different composition and thickness were laid down. You can spot these lens for their distinctive green/purple reflections in place of the weak bluish or yellowish coatings of single coated glass. Then, as the 1970s arrived, they moved on to Super Achromatic and Multi Achromatic coatings but stopped using the terms - they just described the lenses as multicoated. The filters, however, remained labelled as 'AC' or Achromatic Coating - they also made uncoated versions.

David

[01af]

I lifted this from "camerafilters.com": Achromatic (AC) Lens---A new multicoated filter that features color-corrected, 2-element construction. Designed especially for use in combination with zoom lenses having a standard focal range. Recommended for use on 35mm SLR cameras. All require no exposure compensation.

The person who wrote that obviously doesn't have a clue. He confuses filters and close-up lenses, and furthermore achromatic lens design and 'Achromatic Coating' (AC).

Does it have any effect on a digital? If I remove it would it make a difference? Is there a range of other filters for this lens?

Officially, the rear-element filter is part of the lens design, so there must be a filter installed always. If you don't need no filters then the neutral clear-glass filter marked NORMAL is supposed to be installed. Actually, however, you'll hardly notice any difference when using the lens with no filter installed. Instead, with no filter there's a reduced risk on digital of getting a hot-spot flare at the image's center. Optically, removing the filter may cause a slight focus shift---so do not focus with a filter installed and shoot without, or vice versa---and possibly also a minuscule shift of the curvature of field.

There is---or was---a range of 42 mm Minolta-branded filters for the AF Apo G telephoto lenses indeed. These are:

• Neutral (NORMAL)
• Skylight (1A)
• Grey (ND 4×)
• Yellow (Y52, for black-and-white film)
• Orange (O56, for black-and-white film)
• Red (R60, for black-and-white film)
• Blue (KB12, for daylight film and tungsten light; same as Wratten #80B)
• Amber (KR12, for tungsten film and daylight; same as Wratten #85)
• Integral circular polarizing filter

Unlike all the other filters, the polarizer is not a plain 42 mm filter but an integral unit to replace the standard filter holder. It has a thumbwheel so you can rotate the filter as it is installed in the lens. It is rare in the used market, very sought-after and thus, expensive. By the way, the regular filter holder and the integral polarizer unit both will also fit the AF Reflex 500 mm lens' filter slot perfectly.

You can always order regular filters of all kinds in the 42 × 0.5 mm screw-in size from filter manufacturers like B+W or Heliopan (except, of course, the integral polarizer unit). If they don't have that size on-the-shelf they can custom-make them upon special order.

-- Olaf

[bonneville]

Many many thanks. Informative, helpful, interesting and......... without 17 photos of children in silly costumes waving pom poms all over the place. Joy