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Search results

  1. J

    Bird Bath Visitors

    Thanks Don. I am trying to get "good" photos of all the species that comes to the garden. There are about 15 to 20 species (some times I the males and females look different !!. Jeremy.
  2. J

    Bird Bath Visitors

    End of Day visitors Towards the evening a Black Bird flies in - I don't see to many of these: And one of many Top Knot Pigeons: Jeremy
  3. J

    Bird Bath Visitors

    Hello Asher, Just back in the land of the living!! The tape measure? I was using it as a focusing aid. The lens is so close to the birdbath that the sharpness changes depending on where the bird sits so I was trying to get the best compromise. I eventually raised the camera elevation and set...
  4. J

    Bird Bath Visitors

    Here are a couple of pictures of visitors to my birdbaths. I was trying out a remote control for the shutter release. The lens is a 200mm F4 and is about 4M from the bird bath. I am standing about 45M away keeping an eye on the bird bath. While checking the focus and DOF before some "serious"...
  5. J

    The concept of density functions

    Hello Doug, This forum, via your tremendous efforts, really gets down to the nitty gritty !! Yes the psd's do cause concern for some in some areas of communications. Normally one would define the psd as the fourier transform of the auto-correlation function for using this definition it is...
  6. J

    Mitgating image degradation from diffraction

    Hello Doug, Yes it was out of context - sorry. It was one of those mornings. Jeremy.
  7. J

    Mitgating image degradation from diffraction

    Sorry about this Doug, but my mother said : Don't Care was made to care. Don't Care was hung. Don,t Care was put into prison and Made to beat the drum. Jeremy.
  8. J

    Mitgating image degradation from diffraction

    Hi Doug and top of the mornin' to ya, Apologies. SR is the Strehl ratio and may me defined as the ratio of the intensity in the Airy disk produced by the system in question to the maximum intensity available. The max energy in the ideal disc is about 83% of the total energy (the rest is in the...
  9. J

    Mitgating image degradation from diffraction

    Hi Doug, I have a problem here and cannot quite understand what this means : "mitigate the effects of diffraction" ? Our "Camera lenses" in themselves do not exhibit diffraction limited performance - not a big issue here as there are other more important criteria - field flatness, distortion...
  10. J

    Mitgating image degradation from diffraction

    Hi Chaps, My Two pence worth: 1. Re: "we can in theory negate this degradation of the signal by applying an equalizer, a filter whose frequency response is the inverse of the frequency response of the channel" Works well for communications channels - but in the image world ? Is that not what...
  11. J

    Mitgating image degradation from diffraction

    Hi Chaps, My Two pence worth: 1. Re: "we can in theory negate this degradation of the signal by applying an equalizer, a filter whose frequency response is the inverse of the frequency response of the channel" Works well for communications channels - but in the image world ? Is that not what...
  12. J

    Defining more than routine 3-axis "Color Space" from a camera imaging system..

    Hi Doug, WRT to colour in photography etc. I'm still on the learning curve - somewhere at the bottom 1/4 !!!. Re: Some of these are based on a Cartesian coordinate model and some on a cylindrical coordinate model. I'm sure there is a very good reason - but I don't know it. One could play...
  13. J

    Defining more than routine 3-axis "Color Space" from a camera imaging system..

    Hi Asher, Re: Does the color map have to be in 3D space? If you have 3 primary colours thats it - 3-space. Any colour is a linear combination of the 3 primary colours. To produce a colour picture we have 3 planes each plane being an (n x m) matrix where n and m are the size of the image in...
  14. J

    Depth of field: the circle of confusion diameter limit

    Hi Doug and Asher, Yes, very nice write-up. One really has to do a fair bit of reading on this subject and work to get the "most out of it". About diagrams they really help in understanding this topic. I have a couple of interesting equations (gleaned from the www) that relate the near and...
  15. J

    My Experiments => Attn. Asher

    Apologies Doug. Yes I'll learn to do that. Yes Asher the plant on the left is scrappy. That's the sought of thing that happens if one looks through the view finder but does not see. Re: " My feeling is that allocating color, light, shade, contrast, movement and so forth is what gives the...
  16. J

    My Experiments => Attn. Asher

    Hi Bart, Yes determining the coc is hard because of value judgments - What is acceptable sharpness. This is my final picture in this experiment where I try to judge what is a "good" picture of the room. When composing the picture questions came to mind: How important is the potted fern in the...
  17. J

    My Experiments => Attn. Asher

    My 2 Bob's worth: For the 5D Mk1 the F# corresponding to the pixel spacing is in the vicinity of F11 - F12. I don't know if this is a good call as I naively assume all colours fall within 2 pixels perhaps 4 pixel CoC diameter would be a better call for the normal Bayer patterns (?). Yes I...
  18. J

    My Experiments => Attn. Asher

    Hello Everybody, Apologies for the late reply - back after a "mega health check". I'll try to respond to everything. 1. Yes Bart the unit of "Step" is 0.75M one of my unhurried steps. I settled on this after "she who must be obeyed" refused to step out with my tape measure in public places...
  19. J

    My Experiments => Attn. Asher

    Of course. The original size of the image was 4368 x 2912 pixels (Canon 5D Mk 1) and the CoC was 2x8.2 microns (16.6 microns). This gave larger hfd's so there is some slack when setting up the camera. I'll check my notes to see what the HFD was. But in the mean time here is a better documented...
  20. J

    My Experiments => Attn. Asher

    IV'e payed my internet bill (I think) lol. Here is the final result of this work - A reference card for the kit bag. With a quick table: And that abouts finishes this work!! Jeremy.
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