How to crop smartly with Panorama Tools?

Q: Does CROPPING have any effect ?

R: YES, and it can be phenomenal.

Introduction

I am personnally using a Sigma 8-mm EX Fisheye on my Canon EOS 20D.

Anyone using a similar combo, i.e. APS-C size sensor + Circular fisheye lens, may observe exactly all what follows in this article.

I believe that it could also apply to other combinations such as Fullframe fisheye with the same kind of DSLR cameras (e.g. Nikon D70 + 10.5 mm Nikkor).

I shall show exemple using PTGui 5 but PTMac would give the same result. As the later doesn't offer some of the PTGui new functionalities as yet, there will be no equivalent in PTMac in some cases for the moment.

Effect of cropping

It has been often written that cropping has finally no effect on the final panorama and that it is only for having a better "Panorama Editor" image i.e. without black parts.

This can be APPARENTLY true. In fact Cropping has actually always an influence at every further step of the panorama tools workflow but in some case it is hard to perceive it on the final rendered panorama after blending.

Furthermore other factors shall influence the process and may hide partially or totally the real final effect of cropping.

What does the crop do in PTools?

Lets use an analogy: Open a copy of one of the input image of the panorama in your favorite graphic edition application (e.g. Adobe Photoshop). Enlarge the canevas to get a much larger space around the original image. Now use the Crop Tool. You can select either circular or rectangular shape. Crop the image. The selected crop can be smaller, larger, inside the image or partially outside and offset in any direction. when you click on the OK button you have cropped the original image. Only being completely outside of the image excepted any other cropping may have a usefull meaning.

The cropping function in PTGui shall do just that. But it does it "virtually" as the original input image is safely kept as it was before cropping. Only coordinates and dimensions of the crop area are transferred on a script that will be read in the next step by the Optimizer.

Mastering the Crop function

Shape (Type) and size of Cropping (for more details click on button "SYNTHESIS": on top of this page).

The shape of the cropping is controlled by the "Lens type" that is selected in the "Images Parameters" table. If the box "Use individual parameters for:" (on the" Lens Settings" Tab) has been previously checked for that given Image, a rollover list shall appear when the cursor is pushed in the corresponding image line of the "Lens Type"column. You may select whatever type you wish.

The "Lens Type" words can be unfortunatly therefore misleading when cropping is intended. The lens that was used originally for shooting the individual image can be of the same kind than the type of cropping. Alternatively the cropping can be of a different type (shape). When you want to set a specific cropping shape, it is not the "Lens Type"that is really defined in the column but it is the type (shape) of the cropping.

As Panorama tools allow to have different types of lenses for any of the images for a Panorama this means that you may have different "Lens Types"selected in the column. Wathever is the original lens type that you had given in the project first tab page. Just check the adequate boxes of the "Use individual parameters for:" list in the "Lens Parameters" tab and then select the shape of correlated image cropping in the "Images Parameters" tab table.

As an example, for a circular original image, you are then free to select "FullFrame" or "Circular" for one image in the "Images Parameters" table and you shall have rectangular or circular cropping function available in the Crop tab. (This shall appear unfortunately only after having pushed once on the "Optimizer button" though...).

Now you can change the size of the cropped area in that Cropping window or by the dimensions boxes on the right. Remember: the cropped area can encompass only part of the orignal image and include black area void of image.