New Adobe Lightroom 6: Panorama Merge & HDR

Here we are reviewing a feature that works quite in a similar way as the HDR Merge we covered in the episode New Adobe Lightroom 6: Intro & HDR merge, and which enables us to generate a panorama.

What is a Panorama?

A Panorama is an image which is the result of a multiple image stitching process, that provides a rather wide field of view similar to one captured with an extremely wide angle lens without any distortion:

What could one use before LR6 to produce a Panorama?

Before LR6 release, on could use Adobe Photoshop, Microsoft ICE, Autopano…

How does this Panorama process work in LR6?

A minimum of 2 images with common elements in each is required. One can launch the Panorama Merge feature from either the Library or the Develop module via CRTL + M or a right click on one of the images selected: Photo merge -> Panorama:

A new window opens, very similar to the HDR Merge, where there is a preview panel on the left and a few projection and cropping options to choose from on the right. The preview can be enlarged up to 2048 pixels on a high definition display and up to 1024 on a standard one. One can also zoom in by clicking into the preview itself.

What are projections?

Projections are different stitching algorithms, and LR6 offers 3 (each works equally well for both horizontal and vertical panoramas):

Spherical Projection

This stitching method aligns and transforms the images as if they were mapped to the inside of a sphere. This projection mode is great for really wide (such as 360-degree panorama) or multi-row panoramas. The centre part of the image tends to appear closer.

Cylindrical Projection

This stitching method projects the panorama as if it were mapped to the inside of a cylinder. This projection mode works well for wide panoramas, but it also keeps vertical lines straight.

Perspective Projection

This stitching method projects the panorama as if it were mapped to a flat surface. Since this mode keeps straight lines straight, it is great for architectural photography. Wide panoramas may not work well in this mode due to excessive distortion near the edges of the resulting panorama.

How to know which projection to choose?

There is the “Auto-select projection” option, which lets LR6 choose the projection the most suited based on the images one selected. Personally, in every test I have performed, different images, etc. it always ended up selecting the Spherical one.

I’d rather use a projection which produces a content close to the original individual images. In the example, below we can clearly see the effect the Spherical and Cylindrical projections have on the bottom left rock. I believe the cylindrical is here the most appropriate since closer to the captured initial photograph:

Auto crop

This checkbox acts like the crop tool inside the Develop module. Given we are in LR, that crop is non-destructive and can be modified later on in the Develop module. Here what it does is cropping out the white (empty) part of the image that resulted from the Panorama Merge.

The result

Once the projection and cropping option have been chosen, simply hit the Merge button:

The resulting panorama is a DNG file (RAW). This file is not linked to the other initial photographs used which means one can make all the changes possible to it; it will have no effect whatsoever on the other images. That being said, it is worth knowing that should one make any modification to the single images before the merge, not all the develop changes will be kept throughout the Merge; spot modification such as from the adjustment brush, filters will not affect the Merge unlike the basic tone and exposure settings (basically anything that affects the whole image).

LR6 will always try to apply a lens correction profile, when it finds one, to the images before going through the Merge and that even if one did not apply such correction beforehand.

Size matters

The Merge feature in LR6 only works with a resulting image up to 64000 pixels long and a maximum of 512 million de pixels total whichever comes first. Anything that would require being bigger would fail to the process.

Panorama + HDR

It is obviously possible to build an HDR panorama. In theory, there are two ways to achieve that:

1. Create multiple Panoramas of different exposures and then merge them to obtain an HDR: The issue with this method is that a panorama is most likely going to contain most of the information from each of the merged photographs combined. Therefore the resulting file is big in size and lengthwise at least one of its side is almost as long as the sum of the submitted images length. The reason I am mentioning all this is that due to the size limitation of the Merge feature in LR6, chances are if you use RAW files, the merge will most likely fail as it would exceed the limit. I have tested with three panoramas made out of RAW files and got the following error:
2. Create an HDR Merge of each initial photograph before launching the Panorama Merge: This turns out to be the best approach.

Illustration with a fake HDR

I wanted to follow the second approach stated above, but I only had the initial seven images, all of the same exposure.  In the episode New Adobe Lightroom 6: Intro & HDR merge I had mentioned one could create a fake HDR out of one single RAW file.

It is worth noting that the result of an HDR Merge made with multiple RAW files is not the same as the one made from multiple exposures created out of one single RAW file. However, given I only had those seven images, I ended up created two virtual copies for each of the 7. I then changed the exposure setting of the virtual copies; one set to +2 and the other to -2. I ended up with 3 photographs (2 virtual copies + 1 original) which can act as 3 photographs of different exposure level: -2, 0, +2. All I needed then was to select each group of 3 and Merge them into an HDR:

 

Each resulting HDR, 7 in total, was then merged to produce a single HDR Panorama. Given I made a fake HDR, one could have achieved the same result by playing with the black, shadows, highlight and exposure level in the Develop module but this described method is still rather simple and produces an interesting foundation before carrying on further editing.

Conclusion

Is the Panorama Merge feature of LR6 better than the one found in Photoshop and other softwares? Personally, I like its simplicity and the pleasing result. Obviously, Photoshop is more powerful and tolerates more the less-than-perfect images to be merged and that it’s mainly due to its ability to deal with layers. That being said, LR6 is not meant to be replacing Photoshop and that feature, while maybe more limited than of other tools, is not a gadget. I am sure that all the Photographers that do not have Photoshop and are not Panorama aficionados will welcome this new feature just as I do.

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