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Beatsy



Joined: 05 Jul 2013
Posts: 1392
Location: Malvern, UK

PostPosted: Mon Jun 18, 2018 1:24 pm    Post subject: Cog... Reply with quote

...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? Laughing

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.
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dolmadis



Joined: 07 Dec 2011
Posts: 504
Location: UK

PostPosted: Tue Jun 19, 2018 6:29 am    Post subject: Re: Cog... Reply with quote

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.


Inspiring use of a scanner lens, Steve.

Could you spare a mo to post a photo of the arrangement of Raynox to Linoscan and mount to the camera please?

Thanks


John
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Pau
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Joined: 20 Jan 2010
Posts: 4500
Location: Valencia, Spain

PostPosted: Tue Jun 19, 2018 7:41 am    Post subject: Reply with quote

It seems very sharp.
At fist look it seems to have inverted perspective, but measuring with PS ruler it seems orthographic (telecentric?)
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Pau
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rolsen



Joined: 01 May 2018
Posts: 76
Location: Finland

PostPosted: Tue Jun 19, 2018 7:58 am    Post subject: Reply with quote

Really nice!

I have to get one of those Raynox lenses soon, I need it with my point & shoot anyways.

- Rane
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Beatsy



Joined: 05 Jul 2013
Posts: 1392
Location: Malvern, UK

PostPosted: Tue Jun 19, 2018 8:36 am    Post subject: Re: Cog... Reply with quote

dolmadis wrote:
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.


Inspiring use of a scanner lens, Steve.

Could you spare a mo to post a photo of the arrangement of Raynox to Linoscan and mount to the camera please?

Thanks


John


Thanks John. I've put a new post in Equipment Discussions, just in case there are any more comments/questions.

http://www.photomacrography.net/forum/viewtopic.php?p=233508
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Beatsy



Joined: 05 Jul 2013
Posts: 1392
Location: Malvern, UK

PostPosted: Tue Jun 19, 2018 8:43 am    Post subject: Reply with quote

Pau wrote:
It seems very sharp.
At fist look it seems to have inverted perspective, but measuring with PS ruler it seems orthographic (telecentric?)

I had scaling enabled in Zerene, is that perhaps a factor?
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mawyatt



Joined: 22 Aug 2013
Posts: 1633
Location: Clearwater

PostPosted: Tue Jun 19, 2018 12:53 pm    Post subject: Reply with quote

Steve,

Beautiful image for those of us mechanically inclined!!

Best,
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rjlittlefield
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Joined: 01 Aug 2006
Posts: 19335
Location: Richland, Washington State, USA

PostPosted: Tue Jun 19, 2018 3:25 pm    Post subject: Reply with quote

Pau wrote:
At fist look it seems to have inverted perspective, but measuring with PS ruler it seems orthographic (telecentric?)

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.

What are you measuring with PS?

Beatsy wrote:
I had scaling enabled in Zerene, is that perhaps a factor?

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.

By the way, what is the radius of the gear, and how far away from the gear is the lens positioned?

--Rik
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Beatsy



Joined: 05 Jul 2013
Posts: 1392
Location: Malvern, UK

PostPosted: Tue Jun 19, 2018 4:13 pm    Post subject: Reply with quote

rjlittlefield wrote:
...By the way, what is the radius of the gear, and how far away from the gear is the lens positioned?


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.
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rjlittlefield
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Joined: 01 Aug 2006
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Location: Richland, Washington State, USA

PostPosted: Thu Jun 21, 2018 10:50 am    Post subject: Reply with quote

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.

Thanks for the numbers.

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
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Beatsy



Joined: 05 Jul 2013
Posts: 1392
Location: Malvern, UK

PostPosted: Thu Jun 21, 2018 4:34 pm    Post subject: Reply with quote

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.


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.
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