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

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  1. kimmik

    Light throughput equation

    Hi John (apologies!), the first sentence is the key concept, and was stated in a generally applicable fashion. These two polariser prisms offer one example of practical application of the light throughput concept. I have in effect adapted the concept to binoculars as a whole, which are at their...
  2. kimmik

    Light throughput equation

    "The amount of flux which can be transmitted through a prism or other optical element depends on both its angular aperture and its cross-sectional area. The greater the amount of flux which can be transmitted, the better the throughput or light-gathering power (sometimes called étendue or...
  3. kimmik

    Light throughput equation

    Now that the SFL official specs are out, here is the completed Zeiss premium line up, showing well developed patterns: 40, 42 and 54 perform similarly in terms of light throughput per weight 25, 30 and 32 perform similarly
  4. kimmik

    Light throughput equation

    Might be aspherics - cost of aspheric element exponentially rises with size, so larger models fall back to spherical lenses which then limits focal ratio and fov. Slc 56 costs the same as NL 32 after all, despite being way larger.
  5. kimmik

    Light throughput equation

    Somewhat interesting too, that AFOV increases from 250g to 850g, then starts decreasing. Given enough money, there is no reason why the increase in AFOV can't continue. The SLC56 body can take a 75AFOV eyepiece with say eye relief of 16mm. Field curvature will need to be addressed. NL 10x32 is...
  6. kimmik

    Light throughput equation

    Saving it for personal use for now, will post selected data points when needed :). A daylight version would be interesting too, I just don't trust the AFOV figures published by most brands. Swaro seems to publish true measured figures, so might do one shortly for interest. The twilight data...
  7. kimmik

    Light throughput equation

    Definitely a pattern is there. Baseline and standouts. Conquest HD 10x42 is a standout better than other conquests. Swaro NL42 and Curio are standouts out of all other swaro models.
  8. kimmik

    Light throughput equation

    A few others including Henry have also previously said this, that large aperture/exit pupil isn’t just for the low light. It improves the image quality and eye placement. In my view there is no such thing as wasted aperture or wasted light - the more you have to work with the better. Heavier...
  9. kimmik

    Light throughput equation

    Once you have mentally drawn the 10x trendline, the NL 10x42 will be placed better than it, but not by as big a margin as the NL 8x42 is from the 8x trendline. The other way to look at this is that EL 10x50 and SLC 10x56 are already excellent.
  10. kimmik

    Light throughput equation

    Yes and because throughput per weight metric is a major determinant of desirability. Thats why SFL40 is so successful, same throughput per weight (even slightly higher) as the SF42, at a lower price. The market research determines what specification is needed to remain alpha, and the optics...
  11. kimmik

    Light throughput equation

    A lot of good points, i will need to split up my responses. Most immediately would like to point out that 10x always have lower throughput than 8x for the same weight. This is fundamental. I didn’t have a easy way of drawing a separate trendline for 10x models so just imagine one by looking...
  12. kimmik

    Light throughput equation

    Here's a fun one - Curio sits exactly half way in throughput between its two competitors, but closer in weight to the UV. At 250g, it has nearly as much throughput as the 350g CL 8x25!
  13. kimmik

    Light throughput equation

    This plot removed transmission and vignette factors, and just looks at FOV and aperture. Curio and NL 8x42 are clear outliers from the baseline trend.
  14. kimmik

    Light throughput equation

    But did weight alone predict the FOV? The graph makes the chosen FOV obvious. I suspect the point of the graph was not understood. All Zeiss data points assume the same vignetting so it is moot for the last plot.
  15. kimmik

    Light throughput equation

    Throughput vs weight predicts new intermediate Zeiss models almost perfectly. SFL 8x30 will be about 144m FOV. Graph deleted.
  16. kimmik

    Light throughput equation

    graph updated. its next to slc.
  17. kimmik

    Light throughput equation

    7x and 8x chart. Binos towards the top left have better global brightness for weight, FL 7x42 and HG 8x42 are the best. Binos towards the bottom right have worse global brightness for weight, but possibly better contrast depending on how it was optimised. e.g. all Leicas. Center brightness is...
  18. kimmik

    Light throughput equation

    Exactly :). Light throughput vs Weight. I have in mind a graph which will be done when there is some free time, like holger’s AFOV vs k distortion. There will be very interesting patterns emerging. Units are arbitrary as we are comparing, just need to use the same units between comparisons...
  19. kimmik

    Light throughput equation

    I quite like binoculars that have fixed prism and eyepiece, and change magnification purely through objective lens swap. E.g. in addition to your mentioned habicht and E2, also the leica 8x20 and 10x25. They make a lot of sense in that: 1. the 10x has a longer body helping with stability 2...
  20. kimmik

    Light throughput equation

    Would you have any thoughts about the amount of vignetting for 8x vs 10x versions of each model? I haven't paid enough attention to 10x, but wonder if there is less vignetting in the 10x versions, or if the baffle adjusted to achieve the same degree of cats eye at the periphery.
  21. kimmik

    Light throughput equation

    I don't have enough porros to make any generalisations, but the Habicht has fairly low vignetting. Will look up some ak models later and add here. Habicht 8x30 - 75 Habicht 10x40 - 67 The larger habicht is quite good for a 10x, nearly SFL level. Conquest HD 10x56 - 66 SLC 10x56 - 67 FL 10x42...
  22. kimmik

    Light throughput equation

    Since we now know the light throughput, we can do a throughput per mass metric: Zeiss FL 7x42 - 84000/740 = 113 NL 8x42 - 94000/850 = 110 SFL 8x40 - 64000/640 = 100 SLC 8x56 - 118000/1250 = 94 SF 8x42 - 72000/780 = 92 SF 8x32 - 50000/600 = 83 EL 8x32 - 47200/600 = 78 Zeiss VP 8x25 - 22000/290 =...
  23. kimmik

    Light throughput equation

    A couple more examples, which are consistent with my observation: Ultravid 8x20 - 20^2 x 6.5^2 x 0.92 x 0.7 = 10900 Curio 7x21 - 21^2 x 7.7^2 x 0.92 x 0.7 = 16800 Zeiss VP 8x25 - 25^2 x 7.4^2 x 0.92 x 0.7 = 22000 Since these are small exit pupil binoculars, the brightness difference is...
  24. kimmik

    Light throughput equation

    B, no dimming to that degree for surface brightness - slight colour shift and maybe minor dimming in the region of 10 percent in the EL is my estimate. The cats eye vignette has one benefit, it reduces kidney bean as shown in my other thread on blackout. Long eye-relief eyepieces especially...
  25. kimmik

    Light throughput equation

    though your eye is not pointed sideways, the peripheral image light originated from that angle. Wide AFOV and all. These ray diagrams may make the concept clearer. https://www.birdforum.net/threads/ray-optics-simulation-of-swarovski-nl-slw.431120/post-4393153
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