...on a stepper motor. I thought I should try to get *some* use from the pile of film-scanner parts I suddenly accumulated. Wonder how that happened?
Stack of 100 jpeg images shot at 1.4x with a Linoscan 92mm on Raynox DCR-150 as tube lens (not reversed). Got that working much better than it did when I first tried (and rejected) it. The trick was to push the scanner lens right up to touch the glass. The Raynox is 160mm from the camera sensor. I'm not sure if that's how far it's supposed to be, but it works well and is a smaller setup than using the 200mm Hoya as a tube lens.
Cog...
Moderators: rjlittlefield, ChrisR, Chris S., Pau
Re: Cog...
Inspiring use of a scanner lens, Steve.Beatsy wrote:Stack of 100 jpeg images shot at 1.4x with a Linoscan 92mm on Raynox DCR-150 as tube lens (not reversed). Got that working much better than it did when I first tried (and rejected) it. The trick was to push the scanner lens right up to touch the glass. The Raynox is 160mm from the camera sensor.
Could you spare a mo to post a photo of the arrangement of Raynox to Linoscan and mount to the camera please?
Thanks
John
Re: Cog...
Thanks John. I've put a new post in Equipment Discussions, just in case there are any more comments/questions.dolmadis wrote:Inspiring use of a scanner lens, Steve.Beatsy wrote:Stack of 100 jpeg images shot at 1.4x with a Linoscan 92mm on Raynox DCR-150 as tube lens (not reversed). Got that working much better than it did when I first tried (and rejected) it. The trick was to push the scanner lens right up to touch the glass. The Raynox is 160mm from the camera sensor.
Could you spare a mo to post a photo of the arrangement of Raynox to Linoscan and mount to the camera please?
Thanks
John
http://www.photomacrography.net/forum/v ... p?p=233508
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I get it as normal perspective, not telecentric. For me, PS measures the length of the foreground tooth as being 387 pixels, while the length of the farthest back whole tooth that I can see (at bottom of image) is only 378 pixels, so about 2.4% smaller over the radius of the gear.Pau wrote:At fist look it seems to have inverted perspective, but measuring with PS ruler it seems orthographic (telecentric?)
What are you measuring with PS?
Not likely much of an effect, since all scaling tries to do it to adjust the overall size of each frame to match the perspective of the previous one. If you had scaling disabled, then the overall geometry would definitely be orthographic (assuming that you were focusing by moving the whole camera setup). But that imposed orthographic perspective would come at the cost of some softness and possibly even smearing due to details not lining up exactly from one frame to the next.Beatsy wrote:I had scaling enabled in Zerene, is that perhaps a factor?
By the way, what is the radius of the gear, and how far away from the gear is the lens positioned?
--Rik
Gear radius (across opposing tooth points) is 8.38mm and it's 6mm thick. Working distance is 83mm measured from the front of the lens assembly, 87.5mm if measured from the centre of the front element.rjlittlefield wrote:...By the way, what is the radius of the gear, and how far away from the gear is the lens positioned?
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Thanks for the numbers.Beatsy wrote:Gear radius (across opposing tooth points) is 8.38mm and it's 6mm thick. Working distance is 83mm measured from the front of the lens assembly, 87.5mm if measured from the centre of the front element.
Scale change due to perspective goes as subject depth divided by distance to entrance pupil.
So here, we're looking at about 4.2 mm from front of gear to half-way back, versus at least 100 mm from subject to entrance pupil. That would imply maximum 4.2% scale change, less if the entrance pupil is farther back. The calculated number is less than the 2.4% that I measured, but still the point should be clear that small subjects imaged from far away don't have much scale change. We might call the perspective "telephoto" rather than "telecentric", because it's the same flattening effect that long telephotos give in nature photography.
--Rik
Thanks for that Rik. That's how it "looks" to me (like the perspective of a single shot with a 90mm 1:1 macro) - but v. useful to see the numbers behind it.rjlittlefield wrote:We might call the perspective "telephoto" rather than "telecentric", because it's the same flattening effect that long telephotos give in nature photography.