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ZEISS DTI thermal imaging cameras. For more discoveries at night, and during the day.

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  1. B

    Is curvature of field a good thing?

    It may be that the Cooke Speed Panchro f/2 was used. The 50mm f/2 is I think a 7 element 5 group lens of double Gauss type. These lenses, in many different focal lengths, were designed by Horace Lee in 1920 and were used in most movies for perhaps fifty years. There are new production...
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    Kowa 99 Update?

    There may have been only one master optical worker at Kowa. He may have retired. There may be one at Swarovski, one at Leica, one at Canon, one at Nikon and two at Zeiss. There are some in France, U.K., U.S.A., Netherlands, Belgium, Australia, probably Russia and elsewhere. But when they...
  3. B

    What should I do with my 300 video reviews? Request for advice

    Klingon? Regards, B.
  4. B

    Best low- to mid-priced monocular

    Opticron have various monoculars. Regards, B.
  5. B

    Is curvature of field a good thing?

    Space is essentially curved, but so distant that it seems flat. Photo lenses definitely try to achieve flat fields. Even a well made Cooke triplet has an almost flat field. Projecting slides from Gauss type 5, 6 or 7 element lenses the whole field, say 4ft or 5ft wide can be flat...
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    A Cure for Swinging Binoculars

    I think the 6400 must refer to the reticle so called milrad, which is the later Nato standard. Sweden used 6300, later 6400. Soviet 6,000. It should be 6283 (2Pi x1000). I don't think reticles are interchangeable. Regards, B.
  7. B

    Wide flat field and edge sharpness an illusion?

    The best test of edge sharpness is to use a fixed mirror mount and let the stars drift over the field. You then see how awful edge performance is in many binoculars that are perfectly O.K. in normal use. Regards, B.
  8. B

    Determining the date of manufacture of the Hartmann Wetzlar binoculars

    Hi and welcome. The binocular looks genuine, but I don't know when made. The binocular seems to be in good condition, hopefully well aligned and free from internal moisture or fungus. Regards, B.
  9. B

    10x42L vs Nikon MHG

    Firstly, the Fujinons, at least the older 14x40s have an annoying jiggling that makes them unusable for me and others. The image is clean and good but the jiggling unacceptable to me. I did estimate the amplitude and frequency but cannot remember what they are. Yes, indeed, tripod mounted IS...
  10. B

    Challenge - shortest, clearest explanation of why 8x FOV tends to be greater than 7x and 10x

    7x50s are usually either marine binoculars or simple binoculars with fields typically of 7.1 degrees. There are wide field 7x35s, such as the Minolta Standard MK with 11.05 degrees measured field and some up to about 12.5 degrees, but the 7x50s usually have smaller fields. The Minolta Standard...
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    Engravings German WW1 naval binos

    As with all binocular fields measured in angles of degrees or radians, these are spherical or circular measures. Expressing fields of view in linear terms, say metres, is imagining a flat plane or linear measure. As the binocular field gets wider there is more of a difference. However, here...
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    Engravings German WW1 naval binos

    See post 18. This is an O level Mathematics question for 16 year olds. E is the distance in metres. N is 1 divided by the field of view in radians with a possible empirical correction for distortion. In other words, How many field widths of the binocular fill one radian or 57.3 degrees? In...
  13. B

    Stopping down a binocular

    The 8x32BA weigh 640.5g. The 8x32 Conquest HD 628.5g. So 12g or less than 0.5oz difference. Or 2%. I had to change the scales battery and didn't have time to calibrate the scales, but probably correct. Regards, B.
  14. B

    New binos by mid June.

    But, as I said before, you have to buy the binocular you actually test and not some remote binocular, as there is considerable sample variation. Ask B and H if they will give a discount on either the demonstrator or a new one that you actually test. In my opinion it is false economy to test in...
  15. B

    Stopping down a binocular

    Any good optic can lose sharpness if an element is tilted or moved sideways. Today I tested the 8x32 BA against a Zeiss Conquest 8x32 HD. Both were equally sharp, with the Conquest brighter, but personally I don't like the very quick focus as at my normal 120m distance. It was difficult to...
  16. B

    Upgrade to TSN-88 from TSN-883?

    Uusi tai vanha? If you buy a new Kowa, make sure it is a cherry example, as even the top scopes seem to have sample variation, with some being poor optically. So maybe test any new possible purchase directly against your current scope. Regards, B.
  17. B

    Upgrade to TSN-88 from TSN-883?

    It is a personal thing. If there are any defects in your present scope, maybe change. New is not always better. Terveisin. B.
  18. B

    New binos by mid June.

    Hi and welcome. If your daughter liked the two binoculars she tried, one of those is the one to get. However, there is sample variation, so it is important to buy the one you actually try. even if it is the demonstrator. Make sure it is well aligned with no eyestrain. Regards, B.
  19. B

    Best Binocular for...

    Mirage can usually be reduced by viewing from an elevated position. As far as mirage with binoculars, I almost never see this. People must be viewing in awful conditions close to the ground. Mornings or late afternoon mirage is usually less. With telescopes, yes I see it, but usually don't...
  20. B

    Identify binoculars

    Thank you Norm for your help. I also thought K must be a maker's mark. So the binocular may be a useful wide angle model, but with no great monetary value. If in good condition it should be used, as it seems to be. Regards, B.
  21. B

    Identify binoculars

    Looking at the photos it seems to be a multicoated binocular I don't know if it was waterproof originally. There is a finger print or thumbprint on one of the outer surfaces. This should be cleaned very gently with a very small amount of lens cleaning fluid or something like a Zeiss lens wipe...
  22. B

    Identify binoculars

    The diameter is about one inch maybe 25mm. But you have to get the ruler edge right across the centre of the glass. Green suggests multicoating. So probably around 1980. It depends if it has phase coating as it is a roof prism binocular. It could be an 8x22, 8x25 or 10x25. Without the name...
  23. B

    Identify binoculars

    Hi and welcome. In the middle photo the name sticker seems to have been lost. In the first photo there seems to be a worn Japan Institute sticker. So maybe from the 1960s or 1970s. Possibly a Kowa or Kamakura? Maybe 10x25 or 8x22? Are there any JB or JE markings on the front or inside the...
  24. B

    Solar filter for spotting scope???

    Before you start any solar observations, you must be thoroughly familiar with safety. Solar observation by direct means is NOT a fun thing. It is serious. And if you don't know what you are doing, you don't want to risk harm to children or others. Regards, B.
  25. B

    Monarch M7 8x42 problem

    I doubt that, but the optical construction of the binocular may be a factor. Also different exit pupils and colour balance in different binoculars. And different chromatic aberration in different binoculars may enhance the effect. Green and red suggests chromatic aberration is involved...
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