Puzzled by PTGUI Size Increase

[Slobodan Blagojevic]

Panoramas created in PTGUI seem to be "larger than life," i.e., have approximately 12% more vertical pixels than the original file? I understand that some stretching might be involved in order to correct lens distortions, but this seems way too big for that. By the way, panoramas created by Photoshop or Lightroom also vary in size from the original files, but mostly by 1-2%, and that is to account for the staircase-effect, i.e., uneven tripod. Once that is cropped out, the file size becomes a bit smaller than the original.

[Bart_van_der_Wolf]

Panoramas created in PTGUI seem to be "larger than life," i.e., have approximately 12% more vertical pixels than the original file? I understand that some stretching might be involved in order to correct lens distortions, but this seems way too big for that.

Hi Slobodan,

It also has to do with the projection method that has been selected. Actually, since all pixels get resampled, there is no longer an original size, although you can easily specify any size other than the calculated one with the "set optimum size" button. For example, for a single row stitch just type the vertical dimension of a single input file, and the rest follows. Since there may also be cropping applied, I just watch the resulting output size and adjust by percentage if I want an (almost) exact number of vertical pixels, or just crop a slightly oversized stitch afterwards.

Cheers,
Bart

[jrsforums]

I am not sure I understand the importance of the number of pixels.  Particularly if the change does not impact final image quality.

[Slobodan Blagojevic]

I am not sure I understand the importance of the number of pixels.  Particularly if the change does not impact final image quality.

It is the size of objects, as illustrated, not just number of pixels. In other words, people may or may not want something uprezed, for various reasons.

[Bart_van_der_Wolf]

It is the size of objects, as illustrated, not just number of pixels. In other words, people may or may not want something uprezed, for various reasons.

Correct, although just slightly resampling/distorting/warping will already have an impact on per-pixel-resolution. That's why PTGUI uses better resampling algorithms than e.g. Photoshop. The default for general images is Lanczos2, which offers better resolution preservation with only a small risk of adding halos at high contrast edges. It can even be beneficial for quality to create a few more pixels to allow preservation of details in the center of the image, it's a kind of super-sampling which requires more pixels to store the fractional pixel data. Manual overrides are always possible.

This thread may explain a bit more about the choices that PTGUI makes to optimize center image quality.

Cheers,
Bart

[Slobodan Blagojevic]

... PTGUI uses better resampling algorithms than e.g. Photoshop. The default for general images is Lanczos2...

I noticed. When comparing with a PS-generated pano, it is like I forgot to put my reading glasses on 

There are numerous options in PTGUI for resampling... any link with explanation what each one does and is best suitable for?