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Author Topic: Stitched Nikon to emulate medium/large format capture?  (Read 26847 times)
elliot_n
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« Reply #80 on: March 29, 2011, 06:07:49 AM »
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I'm not at a computer with PTGui right now, so has anyone used this feature successfully on single extreme wide-angle shots?


I just loaded a single image into PTGui, but the compression sliders in the Panorama Editor window seem to have no effect. I guess this feature only works with stitched images (?)
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JohnBrew
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« Reply #81 on: March 29, 2011, 06:28:23 AM »
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Elliot, you can download a single image in the new version of Photomatix.
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routlaw
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« Reply #82 on: March 29, 2011, 09:02:35 AM »
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Bernard, thanks for the further clarification. I am encouraged enough to order some pano gear from RRS and give it a try myself.

Rob
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OldRoy
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« Reply #83 on: March 29, 2011, 10:12:22 AM »
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I just loaded a single image into PTGui, but the compression sliders in the Panorama Editor window seem to have no effect. I guess this feature only works with stitched images (?)
Well, I'm using PTGuiPro 9.0.3 and they definitely do compress a single image. Exactly how this compression is distributed I haven't yet had time to evaluate.

Meanwhile I'm off to add some barrel distortion on a few landscape shots to see how much improvement I can make to my amateur efforts. Maybe this is the key to where I've been falling short. Perhaps add a bit of ca for an interesting "halo" effect and a little blur to take the edge of that disturbing sharpness too...

Roy

A quick test reveals that (rectilinear projection mode) compressing the h axis stretches the v axis at the same time. Not, as far as I can see, in proportion to the amount of h compression. Although I haven't tried dialling in random amounts of V axis compression to compensate, I'd say PRGui is useless for correcting this form of distortion.
I'd love to find a solution other than DxO - although it seems that I'm the only person bothered by the volume anamorphosis effect...
« Last Edit: March 29, 2011, 10:30:52 AM by OldRoy » Logged
hjulenissen
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« Reply #84 on: March 29, 2011, 01:20:20 PM »
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B can be emulated by A when A uses a longer focal length (f1>= f2) and stitching to make up for the wider field of view of B.
If one wishes to emulate the effects of using a large sensor with a lense of very large aperture, I am guessing that it can be difficult to find small-format lenses with sufficiently small depth of field (or can this be emulated in the stiching procedure as well?).

If one wishes to emulate the acutance (and aliasing) of typical large-format digital sensors lacking AA-filter, one would have to oversample a great deal, then use "primitive" downsampling, like boxcar filtering.

How does diffraction and diffraction-limits play out here?

-h
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elliot_n
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« Reply #85 on: March 29, 2011, 02:29:35 PM »
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If one wishes to emulate the effects of using a large sensor with a lense of very large aperture, I am guessing that it can be difficult to find small-format lenses with sufficiently small depth of field (or can this be emulated in the stiching procedure as well?).

When you're stitching you are effectively working with a large sensor - often larger than the sensors in medium format backs. For example, a 3x3 grid, shot with a full frame dSLR, with 25% overlap, will give you an effective sensor size of 6cm x 9cm. Getting shallow depth of field with a sensor that large is not a problem. Rather it is difficult to get sufficient depth of field. For a 3x3 grid you need to stop down an additional 2 and a half stops to get the same depth of field as the scene photographed as a single frame.

I shoot my stitches at f11 or f16 (D700) as I want to maximise depth of field. If you shot them at f2 or f2.8 the depth of field would be wafer thin.
« Last Edit: March 29, 2011, 02:34:02 PM by elliot_n » Logged
BernardLanguillier
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« Reply #86 on: March 29, 2011, 06:59:30 PM »
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I shoot my stitches at f11 or f16 (D700) as I want to maximise depth of field. If you shot them at f2 or f2.8 the depth of field would be wafer thin.

Yep, when working with very long lenses with panos covering a wide angle you also start to have problem with focus. Unless you refocus at each frame (which can be done), you end up with a focused area that belongs to a cylinder instead of belonging to a plane. That won't show too much with a closed aperture but might be an issue in some cases at 2.8.

On the other hand most of the panos I did with my 300 f2.8 were of very distant subjects (50 to 100km) and covering a very small angle where these issues can be overlooked totally.

Cheers,
Bernard
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A few images online here!
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