Stereo camera to tilt or not to tilt

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• 05-15-2012, 05:39 PM
Diapositivo
I think you should in theory be able to match two "shifting" lenses by applying the same degree of shift.

If for tilting you mean exploiting the Scheimpflug law, then I don't see it very feasible as the two lenses would have to be tilted by different angles in order to cover, more or less, the same field of view, that I suppose would mean that the brain would not be able to "reconstruct" the image without some headache as the two images would be different.

Besides, I suppose a 3d camera would be optimized for a certain focus distance (let's say: 20 metres, or infinite). If you try to obtain a 3d image of a near object, the two lenses should be mounted so that they converge (just like your eyes do when you observe a pencil that you move toward your nose). Tridimensionality of non-far objects becomes, thus, quite a complicated matter, and one might expect that you want to add tilt to your images because you intend to include some near objects in the frame.
• 05-15-2012, 06:50 PM
JerryWo
Actually, I shoot a lot of stereo using a Manfrotto slide bar and a (Gasp) digital camera. Good stereo requires that both images are taken aimed straight ahead, with the film plane for both photos parallel to the scene. Your camera as drawn, looks fine, I would not tilt the lenses, but you can certainly tilt (aim) the camera in any direction/elevation.

The Manfrotto slide bar keeps the camera parallel to the scene and it can then be moved laterally. Typically the distance is the same distance as between your two eyes....I think that's about 65mm.

It takes a pretty steady hand to take stereo photos manually (using one camera) without a slide bar. With your camera, it would be a snap (pun intended). You would need to ensure that both imaging units are pointed exactly straight ahead, otherwise there will be modest change in scene perspective between the two photos.

Small irregularities are compensated by the eye/brain combo. Your eye/brain combo is definitely NOT used to having two slightly different images. I have a stereo pair where the wind blew (moved) a branch in one photo and not in the other. It literally makes my head hurt to view this pair.

I print 7 x 7 photos and mount them, with the proper spacing, on opposite pages of a scrapbook (or whatever) and view them with a Geoscope. See:
http://www.berezin.com/3d/geoscope.htm

There is a formula for the correct spacing vs. distance to the object being photographed. We humans (unlike owls, etc.) have evolved to perceive stereo at pretty modest distances.

There is an absolute TON of stuff out there on stereo photography. Google stereoscopic.

Enjoy
Jerry
• 05-16-2012, 02:56 PM
himself
Quote:

Originally Posted by filmamigo
Two of the same lens should be matched well enough. I have three different stereo cameras, and two of them are hardly "precision matched": I have an ancient 127-format camera with two simple meniscus lenses, and I have the new Holga stereo with a pair of Holga lenses. Both are perfectly capable of forming decent stereo photos. If anything, I find that stereo improves the performance of a given lens, as your brain combines two separate low-resolution images into one image that appears to have more resolution.

The bigger problem with stereo images occurs when the exposure is not exactly the same between images; our brains don't like seeing the same image with two different brightnesses. I don't know what kind of shutter system you are planning; if it's a shared shutter, or some kind of focal plane shutter, you will be fine. If you are using the leaf shutters on two separate lenses, then I suggest giving them a CLA and getting them to fire at the same speeds.

I was just going to use the leaf shutters.
the stereo camera I use now is a piece of junk and one side is usually overexposed, but it's never been a problem before. I'll keep it in mind tho', thanks.
• 05-16-2012, 03:03 PM
himself
Quote:

Originally Posted by Diapositivo
I think you should in theory be able to match two "shifting" lenses by applying the same degree of shift.

If for tilting you mean exploiting the Scheimpflug law, then I don't see it very feasible as the two lenses would have to be tilted by different angles in order to cover, more or less, the same field of view, that I suppose would mean that the brain would not be able to "reconstruct" the image without some headache as the two images would be different.

Besides, I suppose a 3d camera would be optimized for a certain focus distance (let's say: 20 metres, or infinite). If you try to obtain a 3d image of a near object, the two lenses should be mounted so that they converge (just like your eyes do when you observe a pencil that you move toward your nose). Tridimensionality of non-far objects becomes, thus, quite a complicated matter, and one might expect that you want to add tilt to your images because you intend to include some near objects in the frame.

not what I meant by tilt, well, sort of not... I was thinking more of the "miniature" effect (can't be bothered to google the real name;)) - though it just might look cool.
• 05-16-2012, 03:10 PM
himself
Quote:

Originally Posted by JerryWo
Actually, I shoot a lot of stereo using a Manfrotto slide bar and a (Gasp) digital camera. Good stereo requires that both images are taken aimed straight ahead, with the film plane for both photos parallel to the scene. Your camera as drawn, looks fine, I would not tilt the lenses, but you can certainly tilt (aim) the camera in any direction/elevation.

The Manfrotto slide bar keeps the camera parallel to the scene and it can then be moved laterally. Typically the distance is the same distance as between your two eyes....I think that's about 65mm.

It takes a pretty steady hand to take stereo photos manually (using one camera) without a slide bar. With your camera, it would be a snap (pun intended). You would need to ensure that both imaging units are pointed exactly straight ahead, otherwise there will be modest change in scene perspective between the two photos.

Small irregularities are compensated by the eye/brain combo. Your eye/brain combo is definitely NOT used to having two slightly different images. I have a stereo pair where the wind blew (moved) a branch in one photo and not in the other. It literally makes my head hurt to view this pair.

I print 7 x 7 photos and mount them, with the proper spacing, on opposite pages of a scrapbook (or whatever) and view them with a Geoscope. See:
http://www.berezin.com/3d/geoscope.htm

There is a formula for the correct spacing vs. distance to the object being photographed. We humans (unlike owls, etc.) have evolved to perceive stereo at pretty modest distances.

There is an absolute TON of stuff out there on stereo photography. Google stereoscopic.

Enjoy
Jerry

I was thinking of mounting them both in one lens board so that they would be pointing in the same direction no matter what.

oh, and I know what you mean about the stray object in just one of the images. I have a number of them where an odd branch blows into view at the wrong moment, but I'm hoping that using two lenses firing the same time onto one piece of film will help stop that happening.

my original idea was just to use paper negs or sheet film, so I could just contact print them straight away without needing to mount them latter, but now I'm thinking that some instant pack film will also give me images large enough to just use straight out of the camera.

I did google it, but couldn't (read - gave up too soon) find anything on the effect of tilt on the stereo effect.
• 05-16-2012, 03:36 PM
filmamigo
Quote:

Originally Posted by himself
my original idea was just to use paper negs or sheet film, so I could just contact print them straight away without needing to mount them latter, but now I'm thinking that some instant pack film will also give me images large enough to just use straight out of the camera.

The instant film is a cool idea, it could look really good. Remember though, you need to swap the left-right images on the print. So the instant print will need to be cut, swapped and remounted.

At the risk of angering the Hybrid gods, I will say that I just use StereoPhotoMaker software. It's free and is a boon for printing stereocards or creating stereo output of any kind.

Also, many folks expose slide film and view the images with a slide viewer. Holga now have a 120-format 3D slide viewer and they sell cheap stereo mounts for 120 film.
• 05-16-2012, 03:47 PM
himself
Quote:

Originally Posted by filmamigo
The instant film is a cool idea, it could look really good. Remember though, you need to swap the left-right images on the print. So the instant print will need to be cut, swapped and remounted.

I did not know I had to do that...
shoit
• 05-16-2012, 04:57 PM
Diapositivo
Quote:

Originally Posted by filmamigo
The instant film is a cool idea, it could look really good. Remember though, you need to swap the left-right images on the print. So the instant print will need to be cut, swapped and remounted.

I don't understand why this would be necessary.

The image which is going to be seen by the right eye is bound to be formed in the right side of the paper, or negative (inverted, but on the right half) by the right lens.
The images which is going to be seen by the left eye bound is to be formed in the left side of the paper by the left lens.

When you want to reconstruct the stereo image, you must show the image of the left lens to the left eye, and the image of the right lens to the right eye, or headache will certainly ensue, as - imagine being in front of a convex building corner - the right eye will see the left side of the corner and the left eye the right side.

The father, or grandfather, of an uncle of mine took stereo B&W positive pictures of the front during WW1 on glass plates. Those were to be seen through a stereoscopic viewer with two oculars, which looks like a binocular. The two images were impressed on a single glass plate, which was then put - once developed - into the stereo viewer.

No need to invert the two images, and no possibility either. And, by the way, the images are absolutely spectacular.

Maybe I misunderstood what you mean.

Fabrizio
• 05-16-2012, 05:09 PM
himself
Quote:

Originally Posted by Diapositivo
I don't understand why this would be necessary.

The image which is going to be seen by the right eye is bound to be formed in the right side of the paper, or negative (inverted, but on the right half) by the right lens.
The images which is going to be seen by the left eye bound is to be formed in the left side of the paper by the left lens.

When you want to reconstruct the stereo image, you must show the image of the left lens to the left eye, and the image of the right lens to the right eye, or headache will certainly ensue, as - imagine being in front of a convex building corner - the right eye will see the left side of the corner and the left eye the right side.

The father, or grandfather, of an uncle of mine took stereo B&W positive pictures of the front during WW1 on glass plates. Those were to be seen through a stereoscopic viewer with two oculars, which looks like a binocular. The two images were impressed on a single glass plate, which was then put - once developed - into the stereo viewer.

No need to invert the two images, and no possibility either. And, by the way, the images are absolutely spectacular.

Maybe I misunderstood what you mean.

Fabrizio

that's what I had originally thought having seen some original stereoscopic glass plates...
• 05-21-2012, 10:29 AM
Silverhead
Two of the same lens should be matched well enough. I have three different stereo cameras, and two of them are hardly "precision matched": I have an ancient 127-format camera with two simple meniscus lenses, and I have the new Holga stereo with a pair of Holga lenses. Both are perfectly capable of forming decent stereo photos. If anything, I find that stereo improves the performance of a given lens, as your brain combines two separate low-resolution images into one image that appears to have more resolution.

The bigger problem with stereo images occurs when the exposure is not exactly the same between images; our brains don't like seeing the same image with two different brightnesses.

Agreed with all of this. I too shoot with the Holga Stereo and have noticed the "increase" in resolution (even though technically there isn't any) when the two images are merged into one by the brain. And yes, the brain doesn't like it when the two images aren't matched or in sync...it struggles to put the images together but can't, which becomes frustrating. Thus, I would steer away from tilt...too much room for things to go wrong and mess up the 3-D effect, IMHO.
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