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  1. S

    A question for the technologically minded

    Something I've been pondering recently; hoping someone in the know can fill in the blanks of my knowledge... Is the noise level of a pixel constant (excluding temperature effects), or does it vary with exposure? The reason I ask is that I've been wondering if some sort of pre-exposure (like we...
  2. S

    Mirrorless body for stitching

    I've just realised that foveon's post about vignetting will be correct. The further off centre the sensor is moved, the more <mount> vignetting will occur on the inner edge of the sensor, and LESS on the edge further away from the lens. This means of course that the info lost on the inner edge...
  3. S

    Mirrorless body for stitching

    Looking at front view piccies of the A7R, it looks like you can't even see the whole of the sensor from the front (at 90 degrees) without the bayonet getting in the way.
  4. S

    Mirrorless body for stitching

    I don't think I need mega megapixels, but thinking about it an FF might be better from the point of view of pixel size. Using FF would also mean having less shots to take to cover the same image area. I would still like to be sure, however, that vignetting from the bayonet mount (+ whatever is...
  5. S

    Mirrorless body for stitching

    I haven't seen that before. That's really cute! Not badly priced, either. And looks a great deal easier to carry in the field! I might still have to experiment with my own kit first, though - to make sure it is something I want to be doing, and results are what I expect.
  6. S

    Mirrorless body for stitching

    ...of course I mean vignetting caused by the bayonet mount. ;) Maybe it's not an issue - as I said, I'm having difficulty finding the specifications.
  7. S

    Mirrorless body for stitching

    I hadn't considered that. I was thinking the shift adapter was for cameras with little rear movement, not that it was to be used in addition to the camera movement. My Toyo G would give me 70mm of horizontal movement, to which you would add 2 half sensor widths (one for each side). That would...
  8. S

    Mirrorless body for stitching

    I'm afraid my lack of explanation has struck once again... :o The question is merely to find the most appropriate mirrorless back for use with a 5x4 camera under *normal* stitching usage. The only reason I mentioned the telescope was to give the reason why it had to be a mirrorless back, and...
  9. S

    Mirrorless body for stitching

    My apologies for being terse, it is my way. I frequently don't say enough to make myself understood properly! I'll be using a 'full' 5x4, so I can just use a lens panel and make use of the normal back shift. The problem with the 'scope is that it won't allow a DSLR to move close enough to...
  10. S

    Mirrorless body for stitching

    Not sure if this is the right part of the forum, but... I am contemplating getting a body for use with my telescope and for attaching to a 5x4 lens panel to try my hand at stitching. My 'scope won't focus close enough to allow a DSLR to be used, but I should be OK with a mirrorless body. I...
  11. S

    Distance Sensor to lens

    I found this page (unfortunately not complete) that illustrates the node points: johnlind.tripod.com/science/sciencelens.html This shows how the two node points essentially act as one light path, which explains the still-inverted final image I was expecting.
  12. S

    Distance Sensor to lens

    Thank you for going to the trouble of explaining the different focussing types, Godfrey. I will indeed find a reference and get myself better versed.
  13. S

    Distance Sensor to lens

    I hope I haven't started a flame war here, Leigh - your response to Godfrey seemed a bit harsh. I appreciate that I'm trying to have a discussion on a topic I know little about, but this doesn't make sense mathematically; if you're crossing ray paths twice (or any even number of times), your...
  14. S

    Distance Sensor to lens

    You're suggesting all lenses - including 35mm and MF - focus essentially by using a variable-extension-tube mechanism. If that were true, all lenses would change in length when focussed. And they don't. I assume the rear node changes on 35mm/MF through the use of IF (in some cases), moving just...
  15. S

    Distance Sensor to lens

    Thanks for correcting me, Leigh. I assume the rear node moves on a 35mm camera, where there is some focussing mechanism involved - that's 'cheating' in the LF forum. :) Looks like I need to dust off those books on my shelf and reread what I seem to have forgotten!
  16. S

    Distance Sensor to lens

    Please shoot me if I'm being a numpty, but I thought the general principle was that infinity was at the focal length of the lens from the focal centre of the lens, and 1:1 was twice the focal length. Or is that irrelevant in relation to the lens board, and is only helpful where the lens is...
  17. S

    Balancing foveon colour channels - which filter?

    I managed to get hold of some stronger filters to push this trial as close as I could to what was expected, and it turns out it's not a valid option (not with my results, anyway). The results highlight an issue I was made aware of on another forum; that of a poor performance of the Foveon with...
  18. S

    Balancing foveon colour channels - which filter?

    I still struggle to think in terms of new tech - I keep forgetting that bracketing is no longer a costly option!
  19. S

    Balancing foveon colour channels - which filter?

    I've had a rethink about what I said in my last post, and I'm not sure I agree with myself...! :D If the issue for a particular shot is one of noise with limited light, then what I said previously still stands. If, however, there is plenty of available light (or room to manouvre on the exposure...
  20. S

    Balancing foveon colour channels - which filter?

    I managed to beg, borrow (but not steal) a few filters to play with in order to give this theory a try, and the results unfortunately are not good. First of all, my filter guess was not even close. I ended up putting an 85 and an 85B together... and it was still nowhere near. By my (quick)...
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