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Photo Forum / Digital Photography / DSLR Cameras / September 2005Wildlife photogs need to go beyond camera lenses
I've seen quite a few shots of animals recently where the photogs coudn't get too close, for various reasons. What struck me was that although the shots were sharp, they were obviously heavily cropped because noise was evident in them. Noise in pro DSLRs is "attractive" in a film-like way, but the cropping still reduces the overall quality of the image. If a photog is using a 600mm lens with a converter to get 1200mm, and it's still not enough to avoid heavy cropping, maybe it's time to get away from long refractive telephotos and into reflex systems that would allow much greater focal lengths while maintaining a reasonable focal ratio? The only drawback of course would be the inability to stop-down and the attendent short depth of field. But, there are lens systems out there that can provide focal lengths in the 2500mm range with f6.3 focal ratios. No autofocus though. -Rich >I've seen quite a few shots of animals recently where the photogs >coudn't get too close, for various reasons. What struck me was that [quoted text clipped - 9 lines] >there are lens systems out there that can provide focal lengths in the >2500mm range with f6.3 focal ratios. No autofocus though. And the brokeh looks like what? ---------- Ed Ruf Lifetime AMA# 344007 (Usenet@EdwardG.Ruf.com) See images taken with my CP-990/5700 & D70 at http://edwardgruf.com/Digital_Photography/General/index.html > On Sat, 10 Sep 2005 22:12:52 -0400, in rec.photo.digital.slr-systems Rich >The only drawback of course would be the [quoted text clipped - 3 lines] > > And the brokeh looks like what? Ugly beyond words? I own one mirror lens and it's such a PITA to use and produces such UGLY bokeh, the only thing it can even be used for is maybe a bird or something in water or in the sky.  Signature>>Stacey > > On Sat, 10 Sep 2005 22:12:52 -0400, in rec.photo.digital.slr-systems Rich > >The only drawback of course would be the [quoted text clipped - 9 lines] > bokeh, the only thing it can even be used for is maybe a bird or something > in water or in the sky. Some folks like it, some folks don't. http://mendosus.com/jpg/gumnuts.jpg Some folks don't care either way. This example is a particularly *aggressive* one. -- Jeff R. >> > On Sat, 10 Sep 2005 22:12:52 -0400, in rec.photo.digital.slr-systems >Rich [quoted text clipped - 16 lines] > >This example is a particularly *aggressive* one. That, I admit is pretty horrible. It's a good example of why refractive elements still dominate the field. But some pictures (say a lion on the Savannah) won't produce that kind of effect since specular highlights on the high grass likely won't happen, or will be so subdued that they won't produce that kind of effect. -Rich >>I've seen quite a few shots of animals recently where the photogs >>coudn't get too close, for various reasons. What struck me was that [quoted text clipped - 11 lines] > >And the brokeh looks like what? Maybe we could learn to like the christmas tree-like defocussed circle of light? If the idea is to capture the animal (or whatever) in the best detail possible, and not to make artistic pictures, it wouldn't matter about the background. -Rich >I've seen quite a few shots of animals recently where the photogs >coudn't get too close, for various reasons. What struck me was that [quoted text clipped - 9 lines] >there are lens systems out there that can provide focal lengths in the >2500mm range with f6.3 focal ratios. No autofocus though. Might work for a bird on a wire, or in the sky, but the bokeh would be a mess for an animal in the brush or in a tree. Signature<>>< ><<> ><<> <>>< ><<> <>>< <>>< ><<> John P Sheehy <JPS@no.komm> ><<> <>>< <>>< ><<> <>>< ><<> ><<> <>>< >>I've seen quite a few shots of animals recently where the photogs >>coudn't get too close, for various reasons. What struck me was that [quoted text clipped - 12 lines] >Might work for a bird on a wire, or in the sky, but the bokeh would be a >mess for an animal in the brush or in a tree. There is no way around the blurred "donuts" unfortunately. -Rich >>>I've seen quite a few shots of animals recently where the photogs >>>coudn't get too close, for various reasons. What struck me was that [quoted text clipped - 15 lines] >There is no way around the blurred "donuts" unfortunately. >-Rich Actually, I think there is. The "doughnut" effect is caused by the secondary mirror which is normally placed in the centre of the front refractor (or plain glass) in a mirror lens. This knocks a hole out of the light, which because of the optics is not apparent in perfectly focussed areas but is clearly visible in out of focus areas. There is however a design in which the first mirror (the big one at the camera end) is slightly skewed, and the secondary mirror is off to one side. This means it does not knock out the middle of the image-forming bundle, hence there are (or should be) no doughnuts. ISTR seeing at least one astronomical telescope being marketed recently which uses this design. I have not seen it in any lens sold for photographic use, but I guess this thread was specifically discussing the former. If anyone is interested, I will try to find details, I may still have the magazine which described it. David SignatureDavid Littlewood >>>>I've seen quite a few shots of animals recently where the photogs >>>>coudn't get too close, for various reasons. What struck me was that [quoted text clipped - 37 lines] > >David Only problem; They are very "slow" (f-ratio) scopes. Off-axis Newtonians from Oriontel.com -Rich > If a photog is using a 600mm lens with a converter to > get 1200mm, and it's still not enough to avoid heavy cropping, maybe > it's time to get away from long refractive telephotos and into reflex > systems that would allow much greater focal lengths while maintaining > a reasonable focal ratio? Or to resort to digiscoping. More of a hassle, but much better images when you get it right. http://www.shortcourses.com/how/digiscoping/digiscoping.htm Jan Böhme >> If a photog is using a 600mm lens with a converter to >> get 1200mm, and it's still not enough to avoid heavy cropping, maybe [quoted text clipped - 8 lines] > >Jan Böhme Main problem is speed. I've seen the calculations and when using (for example) and 80mm scope to produce a 2000mm focal length, you're f-ratio becomes 25. Better to invest in a good quality telescope of sufficient aperture and a high quality projection lens (eyepiece) to capture the image. P&S shooters have no choice in this, they have to use an eyepiece to get an image owing to the fact their camera lenses are fixed. Here's a shot I took at 4000mm using a telescope with a 125mm wide front aperture. F-ratio was (4000/125) 32. http://www.pbase.com/andersonrm/image/46946057 Because the lens was an f-8 achromat, and not an apochromat, there is minor residual chromatic aberration, which could be removed in software. The scope itself has a focal length of 1000mm and is about 4 feet long. But I cobbled it together as a hobby project for around $300.00, including it's tripod so it's an inexpensive way of getting focal length. -Rich > >digiscoping. > Main problem is speed. I've seen the calculations and when using (for > example) and 80mm scope to produce a 2000mm focal length, you're > f-ratio becomes 25. Not something for dawn or dusk, agreed. But I have a friend who does digiscoping with a Swarovski ATS-80 HD vith a 20x eyepiece, a digiscoping adapter, and a Nikon CP 995. (He used to borrow my Coolpix, that's how I got into it.) He can get decent pics at full zoom, which would have a focal equivalent of just over 3000 mm, and an f-ratio of just under 40, according to your calculations, also when the bird isn't in bright sunlight. > P&S shooters have no choice in this, they have > to use an eyepiece to get an image owing to the fact their camera > lenses are fixed. Here's a shot I took at 4000mm using a telescope > with a 125mm wide front aperture. F-ratio was (4000/125) 32. I agree that the extra three stops of ISO sensitivity you get in a DSLR must be very useful when shooting through a telescope, and there are cheap adapters that allow a DSLR to me coupled to a telescope. OTOH, then you can't use the camera lens of the digicam for extra zoom. Given the same scope, you get a lot more of both light and sensitivity, but considerably less equivalent focal length. In theory, it should be possible to hook up a DSLR, lens and all, behind a telescope, just as the P&S shooters do with their digicams. Then, one would take advantage of the three extra stops of sensitivity, without having to compromise on equivalent focal length. But I have never seen it done. And nomal lens diameters of SLR lenses aren't exactly ideal for digiscoping purposes. Jan Böhme |
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