Projector lenses etc.

Discuss about cameras, projectors, calibration panels, turntables etc.
Curiousjeff
Posts: 121
Joined: 16 Nov 2016, 22:31

Re: Projector lenses etc.

Post by Curiousjeff »

I have a few Canon lens.

I tried today to put them in front of the lens of the Acer K135, just to see what would happen.

The only lens that could provide a clear image was a 70-300 mm.

The focus point was at 200mm when the front of the lens was at 33 cm from the wall.

The square with the adjustment sliders of the Acer was 4 cm high when seen through the Canon lens.

When the Acer was at 33 cm from the wall without the Canon lens, the square with the adjustment sliders was 5.5cm high.

A large part of the image was not projected through the lens.

Nevertheless, the idea of changing the lens, especially with a zoom feature is very interesting for scanning small pieces.

Jeff
Mongrel
Posts: 20
Joined: 30 Nov 2016, 01:10

Re: Projector lenses etc.

Post by Mongrel »

Curiousjeff wrote:I have a few Canon lens.

I tried today to put them in front of the lens of the Acer K135, just to see what would happen.

The only lens that could provide a clear image was a 70-300 mm.

The focus point was at 200mm when the front of the lens was at 33 cm from the wall.

The square with the adjustment sliders of the Acer was 4 cm high when seen through the Canon lens.

When the Acer was at 33 cm from the wall without the Canon lens, the square with the adjustment sliders was 5.5cm high.

A large part of the image was not projected through the lens.

Nevertheless, the idea of changing the lens, especially with a zoom feature is very interesting for scanning small pieces.

Jeff
Hi Jeff,

My AAXA projector will focus down to 180mm from the front of the lens to the centre of the calibration board. I have no problems calibrating and scanning with a 60mm scale on the calibration board.

Mongrel.
IMG_3257.JPG
Curiousjeff
Posts: 121
Joined: 16 Nov 2016, 22:31

Re: Projector lenses etc.

Post by Curiousjeff »

The Acer K135 can focus at 28 cm (front of projector to wall)

The image projected is 20 x 13 cm

With a close-up lens, I get focus on a 30 mm panel.

The idea was more in regards to the comfort that a zoom lens would provide. Not needing to be so close to the objects.

Jeff
User avatar
Micr0
Posts: 586
Joined: 15 Nov 2016, 15:20
Location: New York City

Re: Projector lenses etc.

Post by Micr0 »

Curiousjeff wrote:The Acer K135 can focus at 28 cm (front of projector to wall)

The image projected is 20 x 13 cm

With a close-up lens, I get focus on a 30 mm panel.

The idea was more in regards to the comfort that a zoom lens would provide. Not needing to be so close to the objects.

Jeff
I was going to buy a 2X 52mm "telephoto" lens to mount in front of my projector and see how that worked. For $10 why not. My motivations in looking at the projector side of the equation were to a, try to get the projector to better match the cameras (easier to modify one lower rez source than to have to change two hi def lenses). The other is when scanning very small objects (50mmcal panels) my camera angles are way too big. I can focus everything at that size , but even using my smaller 720p projector I don't get the cameras positioned where I'd like them.
µ
Curiousjeff
Posts: 121
Joined: 16 Nov 2016, 22:31

Re: Projector lenses etc.

Post by Curiousjeff »

Interesting.

I had a bad experience with too much distortion using simple Vivitar +1,+2, etc.. macro close up filters.

I wonder if this "2X" will induce a lot of distortion ?

If not, it a great idea, and certainly easier then taken apart the projector for a full lens replacement.
User avatar
avogra
Site Admin
Posts: 116
Joined: 11 Nov 2016, 17:27
Location: Munich, Germany
Contact:

Re: Projector lenses etc.

Post by avogra »

I opened my Acer K11 last week and removed the stock optics. Then I tried different lenses in front instead. I had some simple manual photo lenses at hand as well as a lens from an old super8 film projector ( a Leitz Wetzlar Hektor 85mm f/2.5 ).

Overall results where not so great. the projector lens was the most promising. When I moved the lens up and down to get rid of the lens shift, the top corners went very dark. In any constellation, the image had some barrel distortion. Without any lens, the light from the projector is a quite well defined cone. None of my lenses had a large enough back element to catch all the light from that cone. With any lens, I saw quite some straw light in the image.
But it is super cool, how tiny the projected image becomes with a large focal length. The stock lens has somewhere around 15mm. Compared to that the Hektor's 85mm is enormous. The projection at a distance of 50cm was less than 20x30mm in size!

I think I just have the wrong type of lenses at home. Maybe the lens from a slide projector works better? Those should be very cheap to find, at least with the projector attached ;-) Another idea might be lenses for medium or large format photography. Those have a very large flange back distance. But it might be difficult to find those at justifiable price.

Sorry that I didn't take any pictures yet. It was just a quick try and I wasn't satisfied with the results. The projector is still waiting disassembled, so I will repeat it and show you some results anyway :-)
User avatar
VDX
Posts: 36
Joined: 05 Feb 2017, 10:43

Re: Projector lenses etc.

Post by VDX »

... did some tests with modifying projectors and condensing lenses - here a post showing the smallest possible image without and with a condensing lens (achromat) to a Casio DLP:
http://forums.reprap.org/read.php?278,1 ... msg-165840

... here some results with different setups:
http://forums.reprap.org/read.php?278,5 ... msg-610054

... and here, in the attached images a bunch of gears and infos while making the first test:
http://forums.reprap.org/read.php?278,126544


And here a thread from the english sub-forum:
http://forums.reprap.org/read.php?138,20245

Viktor
Viktor
Post Reply