Using PTGui with bracketed images to make panoramic HDRs

PTGui is a powerful piece of panorama stitching software, But how would it cope with making panos shot for HDR?

Shooting bracketed photos to make HDRs can often be hassle enough but shooting bracketed versions of various parts of a landscape, to stitch them together into a panorama? That sounded like serious hassle.

The area that was most worrying me about the whole process was making the HDRs in Photomatix and getting the colour and light right on each part of the proposed panorama. The great thing about modern stitching software is that it normalises the colour between the different frames.

However, having not explored my copy of PTGui enough since getting it, I was very happy to find that it supports HDR imaging. So, armed with 15 images shot last week whilst out with Rob – down in the sewers of Shibuya – I set about finding out whether, being more of a pano software than HDR,  PTGui’s HDR engine was up to the task.

How were the images shot in the first place?

With HDR it is important to limit noise, as the bracketed images are stacked and that can often result in the stacking and compunding of noise if you shoot at too high and ISO. People vary in their opinions on this and there are ways of reducing random digital noise in files shot at a higher ISO. But that is for another posting and I am not going into it here. Safe to say that for the most part, shooting at 200ISO or even 100ISO is best, provided that you are not exposing for over 30secs as the matter of long-exposure-noise then comes into play. This kind of noise can often be worse than high ISO noise.

The five images for each of the three segments of the pano were shot spaced 1-stop apart, with my Tokina 11-16mm f/2.8 lens set at f/7.1. The exposure times were 2sec, 4sec, 8sec [the base exposure], 15sec and 30sec. I fired the tripod-mounted Nikon D300 using an MC-31 cable release.

Camera was tilted up 70 degrees for the top section; level for the middle section and 70 degrees down-angle for the bottom. All were shot JPEG and RAW but I imported the JPEGS into PTGui for this test. For bracketed HDRs, I generally keep RAW files as digital negs which I archive and dont touch.

Lots of complicated GUI…

PTGUi could almost be called ‘God, What A Lot of GUI’, so overwhelming is the Graphic User Interface of the program. But most of the functionality, you will pleased to know, is so good straight out of the box that it means not having to get too far into the intricacies of the progam…. unless of course you want to. Then it becomes something of an onion, so many layers are there.

PTGui: loading the images into the program
PTGui: loading the images into the program
PTGui: lens settings
PTGui: lens settings
PTGui: lots of choices for the type & shape of panorama you want to make
PTGui: lots of choices for the type & shape of panorama you want to make
PTGui: let the software automate the process, or select control points to join the images yourself
PTGui: let the software automate the process, or select control points to join the images yourself
PTGui: settings relating to the HDR tone-mapping, blending and optimisation
PTGui: settings relating to the HDR tone-mapping, blending and optimisation
PTGui: choose your output size, file-type and create the panorama

PTGui: choose your output size, file-type and create the panorama

What settings to use?

With so many settings, how do you go about setting the program up for the best results? Well, to be honest, as with most bits of software there is a lot of learning as you go along. The first mistake I made was choosing to putput the file as a .TIFF at ‘maximum size’, which started generating a file about 17,500 pixels long on the long side. It took ages and I found I had selected something wrong about the sidecar HDR file. Half-an-hour later, I had a 455mb sized format of TIF file which I couldn’t open in Photoshop. Back to the drawing-board!

Trial and error won-out in the end!

I was familiar enough with the panorama stitching part of PTGui to know what I was doing; i.e. set the basic parameters of output size, panorama orientation and style, then use the panorama editor [see below] to set a centre point true to the horizon of the image, and finally to alter the vertical and horizontal fields of view to keep the black borders to a minimum. But as far as the HDR was concerned, I was in the dark. So, time to play!

PTGui: editing and aligning the panorama, to give it a centre point and to adjust the vertical and horizontal fields of view, which result in less or more black around the image.

PTGui: editing and aligning the panorama, to give it a centre point and to adjust the vertical and horizontal fields of view, which result in less or more black around the image.

Optimising the HDR through PTGui

I found that the best results were definitely gained by selecting ‘True HDR’  and then asking PTGui to ‘Optimize’  the HDR colour and tone settings. All this is accessible from the ‘HDR’ tab in the interface. As well creating the file in a format you choose [.PSD, .TIFF, .JPG etc], PTGui also creates a 32bit .HDR file. This is editable in Photoshop and was what I worked on to get the final result.

It was important not to get carried away with creating too big an image. PTGui has presets available for ‘web’ and ‘print’. I chose the ‘print’ preset, which creates an image at a sensible size, with perfectly adequate resolution and which ended up – in my case – being around 4000pixels on the long side and about 9.5mb. The companion .HDR file ended up at roughly 38mb. The files took about five mins to generate.

So, for a panorama creation program, how was the HDR quality?

Very good, actually. The images below show – in order – the .PSD file [a little flat for colour], the .HDR file [very good quality as compared to Photomatix] and the version I cropped ready for final editing in Photoshop using my usual set of workflows: Nik Colour Suite 3 etc. All the images below have been rezzed-down for web from their original 4000pixel height. It was more the colour depth I was interested in showing you here. Take it from me that the sharpness, lack of noise and good detail in the outputted images was very good indeed.

The .PSD files, straight out of PTGui. Original size was 4000pixels on the long side.

The .PSD files, straight out of PTGui. Original size was 4000pixels on the long side.

PTGui: the .HDR file as i came straight out of PTGui. Original size was 4000pixels on the long side.

PTGui: the .HDR file as i came straight out of PTGui. Original size was 4000pixels on the long side.

PTGui: the version I cropped and rotated, prepared for stylising in my usual manner, with Nik and Photoshop.

PTGui: the version I cropped and rotated, prepared for stylising in my usual manner, with Nik and Photoshop.

So, how does PTGui deal with creating Quicktime VR?

Again, well. Creating these sorts of panoramas is, again, a bit of trial and error until you get the correct workflow and settings. But the one I created from these shots is pretty good, all be it without the final image stylising I was able to do in Photoshop for the ‘still’ image you see at the foot of this page. However, the HDR blending in PTGui is good enough to create Quicktime VTR panoramas from bracketed shots to a perfectly good level of quality.

You can see mine by clicking here. You will need Quicktime to view the image, which is 922kb in size.

And the final shot?

My final rendering of the image was from the cropped version you see above, edited using Nik Creative Suite 3 and Photoshop CS3. I applied contrast and lighting changes, some selective darkening and lightening, a little colour stylizing – fading back each of the filters a good portion as I went along. Tonal contrast filters and Define were used to sharpen. The whole process – from import of the original images into PTGui, to the final image you see below – took about 30mins.

The Shibuya-gawa in bracketed HDR and vertical panorama, by Alfie Goodrich

The Shibuya-gawa in bracketed HDR and vertical panorama, by Alfie Goodrich

For details of the photography classes we give in Tokyo, go to this page. As well as classes on shooting, we also run Photoshop, HDR and various other workflow classes.

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