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    Re: Schneider Apo-Tele-Xenar 600/9

    You can definitely use a longer lens than 400 mm on your Technikardan. I use the (non-telephoto) 450 mm Fuji-C.
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    Re: 150mm Xenotar - radioactive?

    Some Xenotars are radioactive from thorium glass, others are not. It seems early ones have the thorium glass.
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    Re: Repro-Claron f/9 210 mm

    This process of the daughters growing to their equilibrium concentration is what I was describing in my 04:23 message yesterday. The graph at the URL given by Steve makes it easier to understand --...
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    Re: Repro-Claron f/9 210 mm

    I have measured many lenses with thorium glass. Over a 2 inch diameter Geiger detector the count rate is typically at least thousands per second, not approximately one per day.

    Yes, the Wikipedia...
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    Re: Repro-Claron f/9 210 mm

    Yes, I mis-typed when I wrote 238 instead of 232.

    But it isn't safe to assume that there is no radium in the glass or that the vast majority of the radioactivity comes from the first step. ...
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    Re: Repro-Claron f/9 210 mm

    It is true that natural thorium, Th-238, is an alpha emitter, but Th-238 decays into a series of radioactive isotopes, which together emit a mixture of radiations, including gamma-rays. The...
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    Re: polaroid film

    The 550 Polaroid holder takes 4x5 PACK film. http://www.rwhirled.com/landlist/landfilm.htm indeed has the list of films for this holder, but that webpage is out of date in its statement that those...
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    Re: Fujinon-SF 250 mm lens

    It is necessary for some small lensboards (e.g., Linhof Technika) to use the spacer in front of the board to make it possible to mount the board with the large Copal 3 shutter onto the camera --...
  9. Re: Light falloff on wide angle lenses.

    cos^4 33 degress = 0.5, so 1 stop. But the Nikkor-SW series uses the large, negative outer elements just like the Super-Angulon series, and thus the tilting pupil trick to improve off-axis...
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    Re: Scheinder super WA lenses for 8x10

    With the Super-Angulon you will be less likely to want to use a center filter, for two reasons. First, because it is a longer focal length. Second, unlike the Super-Symmar-XL, it uses the tilting...
  11. Re: Exposing your film with a CTX 5500 Machine

    The above is an image from the Kodak article "Baggage X-ray Scanning Effects on Film", http://www.kodak.com/global/en/service/tib/tib5201.shtml
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    Re: Copal shutter diameters

    There are tables at http://www.skgrimes.com/products/index.htm and http://www.rtsphoto.com/html/copal2.html: 29.0 x O.5 mm for Copal 0 and 40 x O.75 mm for Copal 1.

    I think I've seen the product...
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    Re: The Order of Stacked Filters

    Here is a better explanation from http://www.ptonline.com/articles/200512fa2.html:

    "When polarized light passes through transparent or translucent plastic, the components of the light wave that...
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    Re: The Order of Stacked Filters

    Plastic, if stressed or carrying internal stress, will show interesting colored patterns if observed between two sheets of crossed polarizing material. Sometimes natural light is already partially...
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    Re: Ok, ok, I screwed up...

    Both Nikkor-SW lenses that I have shims between the shutter and the front cell. I have a small yellow paper warning insert that came with some LF Nikkor (probably one of these) that lists a...
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    Re: Pentax Digital Spotmeter prices

    There are always strange price examples on eBay. Perhaps someone didn't check prices, or got caught in a bidding battle and bid too much. But maybe a high price for a Pentax Digital Spotmeter...
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    Re: Nikkor shutters

    This isn't some special property of Nikon shutters, nor should it be unexpected. The equation for the f-stop N is N = focal length / aperture diameter. So two lenses of different focal lengths...
  18. Re: B&H Photo: Kodak Portra 8x10 NC not more available

    The title of this thread isn't precisely correct since a Kodak Portra NC film is available in 8x10 -- 400NC accordinging to the post by Eric. I found it listed in stock by Calumet.

    Maybe more...
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    Re: center filter question

    You can obtain the specs (e.g., 86 mm front threads, as stated by Helen) and Schneider's instructions at www.schneiderkreuznach.com/pdf/foto/centerfilter.pdf.

    The center filter is designed to be...
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    Re: Hyperfocal distance

    The equation relating object distance So and image distance Si is given in the Lens Tutorial at http://www.photo.net/learn/optics/lensTutorial. So for f=75 mm and So=2500 mm, Si= 77.32 mm. The...
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    Re: Hyperfocal distance

    When the lens is focused on infinity, the distance from the image (i.e., film) to the REAR nodal point or principal point will be 75 mm. So you can simply focus on infinity and measure 75 mm...
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    Re: DOF and printed image

    The value commonly quoted for the resoloving power of the human eye is 5 lp/mm, but there isn't a sharp cutoff. If you decide that you want, say 4 lp/mm on the print that is a 2.3X enlargements,...
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    Re: LF vs MF lens quality

    I tested my 110 mm Super-Symmar XL on 4x5 film, and with some shift applied. While the center was sharp at f11, the corners hadn't reached their potential yet. You probably lose a little sharpness...
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    Re: filter for Schneider 210mm SS XL

    Assuming an index of refraction of 1.5 (which is reasonable), a glass filter on the rear shifts the focus by 1/3 the thickness of the filter. Obviously this is much less than a centimeter. In some...
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    Re: Lens Design For Maximum DOF

    Several questions are being asked here.

    Leonard pointed out a full version of the DOF equation that includes the pupil magnification, rather than ignoring this factor. One version on the web is...
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    Re: Lens Design For Maximum DOF

    The f-stop is defined as the focal length divided by the diameter of the entrance pupil. The pupil magnification is the ratio of the diameter of the exit pupil over the entrance pupil. So for two...
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    Re: film holder depth- ANSI spec?

    Edward Hoover has posted the ANSI specifications at http://home.earthlink.net/~eahoo/page8/filmhold.html. The depth to the septum for 4x5 holders is 0.197 +/- 0.007 inches (5.0 mm), that of 8x10...
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    Re: Need some bulb advice

    The first lamp looks better than the second and third. It outputs more lumens so that it will be brighter. It has a color temperature (5500) that will be good for for daylight film. It has a...
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    Re: Focus accuracy - what's acceptable

    Your right, collimating through a lens wouldn't make sense for virtually all LF cameras since the position of the lens isn't fixed with respect to the back.

    We went over the configuation of the...
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    Re: Focus accuracy - what's acceptable

    Using the equations for focusing a lens of focal length f=150 mm, an object distance of 10 ft (3048 mm) corresponds to an image distance of 157.76 mm; for an object distance of 10 ft 6 in (3200.4...
  31. Re: Colorshifts in edges of Rodagon lenses

    You have probably seen lenses with separation. The optical cement has failed between two elements that should be glued together. The colors are Newton's rings -- an interferrence phenomena of the...
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    Re: An unusual Sironar

    You can't buy this exact lens new, only its descendent. Rodenstock uses the "Sironar" name for their plasmat-type lenses. The plain Sironar was circa 1960s/1970s. The current versions are the...
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    Re: Center of perspective and nodal point

    Kudos to Mr. Freaza for conducting this experiment, but let's be clear about what he has shown. He tried rotation axes 23, 64 and 90 mm from the film plane, obtaining parallax free results with the...
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    Re: Center of perspective and nodal point

    There are at several cases of panaromaric cameras. I think Leonard is addressing the case where a conventional camera is rotated to take a series of photos. It seems that the answer for this case...
  35. Re: Is B+W 092 Filter Still Good With New Rollei Infrared Film???

    The IR responses of these three films shouldn't be a mystery -- the spectral response curves are published in the datasheets. In my first answer I compared the new Rollei IR to the Macro IR. ...
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    Re: Coverage of 400mm Fujinon-T

    A Fuji paper brochure that I have lists 220 mm diameter at f22 as the coverage.

    If you have the lens stopped down to f22 and look through the lens, directly on axis, the aperture should look...
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    Re: Focus screen foulup - I think

    I answered this in my second answer, of timestamp 03:00.

    Bowed Linhof SuperScreens are a common but not universal problem. Ken mentioned his experience above. Other discussions that mention...
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    Re: Focus screen foulup - I think

    If the screen is bowed this much, it needs to be replaced. The mounting method sounds correct. If you remove the clips by removing the four screws, you will find two metal strips which positon the...
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    Re: Focus screen foulup - I think

    I've never had one, but from reading other postings, I think that the Beattie screen is an integral screen that combines a frosted surface and Fresnel lens into one piece of plastic. or maybe with a...
  40. Re: Center Filter for 150mm Super-Symmar XL

    As Eric says, I'd first try not using a center filter, then using trying your existing IVb center filter.

    If you look at the footnote in the pdf file that Ling linked, while Schneider recommends...
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