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Photo Forum / Film Photography / Darkroom / November 2005Using Ilford Multigrade below lens
Can I cut down a set of Ilford Multigrade 3.5" filters for below-the-lens use? In other words, are below-the-lens filters different in any way optically? Mike spake thus: > Can I cut down a set of Ilford Multigrade 3.5" filters for below-the-lens > use? > > In other words, are below-the-lens filters different in any way optically? Yes, worse, because they can degrade the image (more easily than above the negative). However, if they're kept clean, you should still be able to get decent prints.  Signature... asked to comment on Michigan governor George Romney's remark that the army had "brainwashed" him in Vietnam—-a remark which knocked Romney out of the running for the Republican nomination—-McCarthy quipped, "I think in that case a light rinse would have been sufficient." (Eugene McCarthy, onetime candidate for POTUS) > Can I cut down a set of Ilford Multigrade 3.5" filters for below-the-lens > use? > > In other words, are below-the-lens filters different in any way optically? Yes they are- dust and scratches are more likely to be seen. Best place to put them is above the negative if you don't have a in the lamp house drawer. SignatureLF Website @ http://members.verizon.net/~gregoryblank "To announce that there must be no criticism of the President, or that we are to stand by the President, right or wrong, is not only unpatriotic and servile, but is morally treasonable to the American public."--Theodore Roosevelt, May 7, 1918 Are there glass filters available for this purpose ? >> Can I cut down a set of Ilford Multigrade 3.5" filters for below-the-lens >> use? [quoted text clipped - 5 lines] > to put them is above the negative if you don't have a in the lamp house > drawer. > Are there glass filters available for this purpose ? The question your asking is does someone make a ready made boxed set....my answer is not to my knowledge. In the 25 years of my photo existence I haven't seen them but that doesn't mean they don't exist. You could use any screw in type on the lens if it has threads, but its a PITA. You certain can buy glass or resin filters if money is inconsequential . SignatureLF Website @ http://members.verizon.net/~gregoryblank "To announce that there must be no criticism of the President, or that we are to stand by the President, right or wrong, is not only unpatriotic and servile, but is morally treasonable to the American public."--Theodore Roosevelt, May 7, 1918 > Can I cut down a set of Ilford Multigrade 3.5" filters for > below-the-lens > use? > > In other words, are below-the-lens filters different in > any way optically? Filters are more critical in the image path than in the light path. If the filters are very clean, free of scratches or blemishes, and are homogenious they will work fine in the image path. The last is important. The filters should not distort when you look through them. Also check by moving one around in front of the lens, there should be no effect from this. In theory, flat block with parallel surfaces will have no effect on light which is collimated. This is usually the case when a filter is used on a camera. The light from the objects is far enough away so theat the light rays are nearly parallel. When used in a convergent or divergent beam the block can introduce aberrations. The amount depends of the thickness and the index of refraction of the material. When its necessary to use a filter in an image forming path where the light is vergent the best material is gelatin since it is thin and the index is close to that of air. The plastic filters used for some VC filters has a higher index than gelatin but is still better than glass. So, the effect of lamp house type VC filters used below the lens, should be minimal, provided they are in excellent condition. I've given a somewhat long answer so you will know what the factors are here. Signature--- Richard Knoppow Los Angeles, CA, USA dickburk@ix.netcom.com > Can I cut down a set of Ilford Multigrade 3.5" filters for > below-the-lens > use? > > In other words, are below-the-lens filters different in > any way optically? I left out a line, namely that the light rays from an enlarging lens are vergent rather than plane. Again, the the practical effect of this in enlarging as far as introducing aberrations from a thin film filter are minimal. Signature--- Richard Knoppow Los Angeles, CA, USA dickburk@ix.netcom.com >Can I cut down a set of Ilford Multigrade 3.5" filters for below-the-lens >use? > >In other words, are below-the-lens filters different in any way optically? Why not buy the real thing? Ilford offers a set of Multigrade filters that are specifically designed to be used below the lens. http://www.pictureline.com/product.php?id=1645 If you want to see what they look like, there is a set for sale on eBay UK. http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7562708722 Tony Polson wrote: >>Can I cut down a set of Ilford Multigrade 3.5" filters for below-the-lens >>use? [quoted text clipped - 10 lines] > > http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=7562708722 Text in French, but just scroll down to the bottom for pictures of how it fixes to the lens. http://www.nightlight.fr/Pagesproduits/charte_gris_neutre_kodak.htm FYI, the text below the pix talks about the filters in general and not how the fixation works. Mike <mike@example.com> wrote: >Can I cut down a set of Ilford Multigrade 3.5" filters for below-the-lens >use? Should work fine. If they are as good at the 6"ers I have I don't see any problem. But that means NO scratches, fingerprints, globs, blobs and/or dust. If they need cleaning then test the cleaning method on the 0.5" strips you have cut off. You wont get the filter frames, filter holder and storage box the underlens set comes with. To keep the set ebayable you might make a cardboard under-lens gizzy to hold 3 1/2" filters. If you cut them they are yours for life; if you decide to get a real set of UL filters then you can lessen their $$ by selling the old 3 1/2's. == On a related matter == I once cleaned an under-lens Polymax with water & stuff. I can't vouch what the stuff was, probably Windex or distilled water on the end of a Q-tip. I wondered where the yellow went When I examined the Q-tip it was evident Don't apply anything waterish to below lens filters. Any one want a perfectly clear filter labeled "2 1/2"? SignatureNicholas O. Lindan, Cleveland, Ohio Consulting Engineer: Electronics; Informatics; Photonics. To reply, remove spaces: n o lindan at ix . netcom . com Fstop timer - http://www.nolindan.com/da/fstop/index.htm > == On a related matter == > I once cleaned an under-lens Polymax with water & stuff. I can't > vouch what the stuff was, probably Windex or distilled water > on the end of a Q-tip. I once handled a standard above-the-lens filter with moist fingers. the dyes comes off like watercolour :-( Now, I never let them get close anything liquid. > I wondered where the yellow went > When I examined the Q-tip it was evident > > Don't apply anything waterish to below lens filters. Any one > want a perfectly clear filter labeled "2 1/2"? Mine being a "3 1/2" with a clear patch :-) On Tue, 15 Nov 2005 14:14:30 +0000, Tony Polson wrote: >>Can I cut down a set of Ilford Multigrade 3.5" filters for below-the-lens >>use? [quoted text clipped - 3 lines] > Why not buy the real thing? Ilford offers a set of Multigrade filters > that are specifically designed to be used below the lens. Because I bought a 3.5" set for really cheap. I already have a set of old Kodak below-the-lens filters, but they are old and I really don't think the grades as indicated by the numbers are at all accurate. Which isn't a problem, but I also think the leaps between filters is too big. For example, going from 2->2.5 is not much, but going from 2.5->3 is huge. > Kodak filters, Ilford paper: going from 2->2.5 is not much, > but going from 2.5->3 is huge. For illustrative purposes only. These are relative numbers applicable to a specific setup and measurement technique. Your mileage will be way different, but they give a good idea of what is going on. The first is RC pearl, the other FB glossy w/ferrotyping and Selenium. The illumination measurement technique is different between the two. The reason for presenting disparit data is that the first set is the only set I have with Kodak filters and Ilford paper. Polymax filters. Only filters with a meaningful difference are shown: Filter -1.0 0.0 1.5 2.0 3.0 4.0 5.0 .13->1.9 OD 4.9 3.7 3.2 2.9 2.5 1.9 1.4 stops of exposure on the paper (Zone I-VIII) Things are a bit better with Ilford filters/Ilford paper, unedited: Filter 00 0 0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.0 .13->1.9 OD 4.8 4.4 4.2 3.8 3.4 3.1 2.9 2.5 2.2 2.0 1.6 1.6 on the paper -Wonder why a timer and baseboard light meter that work in stops would be so useful here ...- -- Nicholas O. Lindan, Cleveland, Ohio Consulting Engineer: Electronics; Informatics; Photonics. To reply, remove spaces: n o lindan at ix . netcom . com Fstop timer - http://www.nolindan.com/da/fstop/index.htm >Tony Polson wrote: >> Why not buy the real thing? Ilford offers a set of Multigrade filters >> that are specifically designed to be used below the lens. > >Because I bought a 3.5" set for really cheap. Like $27 is expensive? OK, it is $27 plus shipping, "Tony Polson" <tp@nospam.co.uk> wrote > Like $27 is expensive? OK, it is $27 plus shipping, I think we have all been in the place where $27 is expensive at sometime in our lives. SignatureNicholas O. Lindan, Cleveland, Ohio Consulting Engineer: Electronics; Informatics; Photonics. To reply, remove spaces: n o lindan at ix . netcom . com Fstop timer - http://www.nolindan.com/da/fstop/index.htm On Tue, 15 Nov 2005 23:50:58 +0000, Tony Polson wrote: >>Tony Polson wrote: >>> Why not buy the real thing? Ilford offers a set of Multigrade filters [quoted text clipped - 3 lines] > > Like $27 is expensive? OK, it is $27 plus shipping, I got them for $5. If I can save $30 by spending 30 minutes to cut them down to size and fit in my existing below-the-lens carrier, then yeah, it is worth it to me. >On Tue, 15 Nov 2005 23:50:58 +0000, Tony Polson wrote: > [quoted text clipped - 9 lines] >down to size and fit in my existing below-the-lens carrier, then yeah, it >is worth it to me. Fair comment, especially as you already have the carrier. |
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