Author Topic: Batch processing HDR images  (Read 689 times)

Seapy

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Batch processing HDR images
« on: December 26, 2018, 09:28:34 »
Now I have my D800 I have started copying my fathers plant and flower slide collection taken around 1965 with a Zeiss Contaflex using Kodachrome and Ektachrome film. I am using the micro Nikkor 55 f/2.8 on the PB4, as intended, I can nicely get ~1:1 .  In most cases the shadows are rather underexposed, leaving the slides with difficult dark detail and some over exposure of say flowers in the sunlight, depending on the lighting.  My solution is to make five bracketed exposures at 0.7EV steps, using HDR in Lightroom this seems to allow me to recover a reasonable exposure range in the finished image and extract better shadow and highlight detail.

For this batch of slides I will need to perform HDR on several hundred slides, times five exposures per slide, that is quite a bit of work.  Taking the exposures is easy enough, processing them as HDR in Lightroom is very time consuming.  Is there any way to automate the HDR process using say, Bridge and Photoshop to produce the HDR images in batches, allowing me to get on with other stuff while the files are processed.  I am slightly aware of actions but have no experience of batch processing.  I have always taken the view that by the time I had learnt the process and set it up I could have done it the slow way by hand.  This time I believe the processing automation would be worthwhile.

I expect I would need to put each batch of five bracketed exposures in a sub folder to identify the batch sets, but beyond that I am lost, none of the tutorials I have found apply to HDR processing.  Lightroom does it very easily but needs the batches selecting and feeding manually, which ties me up and prevents me from getting on with other tasks.

This is a typical example of a photograph taken at the Chelsea Flower Show 1965 before HDR processing and after.

The first image is pretty well what the slide looks like to the naked eye.
Robert C. P.
South Cumbria, UK

armando_m

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Re: Batch processing HDR images
« Reply #1 on: December 26, 2018, 16:20:36 »
I searched and seems to be something many people would like to do - batch process hdr

Have you already done thee 5 shots per slide ?

The difference you show seems very well within the range of what is possible to do with just shadow/highlight sliders in LR, specially with a D800 NEF file at 100 ISO

Please excuse me I hope this comment does not come across as inappropriate, I maybe missing the point but it sounds like overkill to shoot hdrs from a negative if details are not visible in the negative no amount of hdr will be able to extract them
Armando Morales
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Seapy

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Re: Batch processing HDR images
« Reply #2 on: December 26, 2018, 19:35:26 »
Thank you for your observations Armando, yes, I have made five shots per slide for 90 slides, I have perhaps another 200 more slides to process.  In fact I have been multitasking all day, cleaning the house, every time I pass the computer I hit the button to process another set of five!  I have now HDR processed all the exposures I have taken, all are as good as I hoped.

As for your suggestion I could achieve the same results by adjusting the image, I feel the extremes of exposure from a single shot mean that you might be able to get acceptable results, but I feel the colour density suffers when you push or pull the shadows and highlights, overstressing the image, whereas this way I get the best possible chance by layering the image, which is effectively is what the HDR process does, without pushing or pulling too much.

I got the idea from stacking night time sky images to bring out the star colours and detail in the sky by intensifying the lights without touching the darks.

By the time I have taken sample images to get an optimal exposure (the camera metering seems to struggle with some images).  I can tell when the camera is wrong, especially with a dark image.  In that time I could have run off five bracketed exposures for HDR with a bit of extra latitude.

When I have finished the slides, I plan to set about my negatives, I have no idea how many I intend to digitise but I don't expect to have to HDR them.

Not sure I have explained it well but hope you understand.  It would have been good to be able to run batches but not to worry, will get there in the end.  ;D
Robert C. P.
South Cumbria, UK

CS

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Re: Batch processing HDR images
« Reply #3 on: December 26, 2018, 22:04:55 »
Perhaps like Armando, I'm confused about HDRing already exposed images. I get HDRing original photos where one can take in more DR than could be captured in  single exposure. But, I don't know how that works for copying an exposed image, where one is limited to the DR of the exposure. YMMV
Carl

Seapy

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Re: Batch processing HDR images
« Reply #4 on: December 26, 2018, 22:59:27 »
The way I see it is this, in a slide the visible range is compressed, drastically, if you shine a bright light through the transparency you can make out detail which isn't normally visible, equally if you shine a dim light through the 'thin' parts of the image you can see detail which would be blown out with the bright light.

In order to capture the faint detail at the bright end, short exposures gets the job done, at the dark end, a much longer exposure reveals the hidden detail that otherwise would be lost, over 5 exposures I gained three and a half extra stops of range, revealing blown highlights and dark detail otherwise hidden, had I not used the extended exposure.

The HDR process simply blends these images together to provide a balanced exposure in the final image.  The histogram from the HDR process has an excellent spread of data.

I don't completely understand the technical side of this but it works well, turning poorly exposed transparencies into nicely spread images where you get to see the shadow detail and the highlight detail.  I use HDR quite often, even for 'normal' photographs if the expected range  of light is excessive, especially sunrise/sunsets etc.
Robert C. P.
South Cumbria, UK

pluton

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Re: Batch processing HDR images
« Reply #5 on: December 27, 2018, 03:43:42 »

The difference you show seems very well within the range of what is possible to do with just shadow/highlight sliders in LR, specially with a D800 NEF file at 100 ISO


This was may thought also.  It has been my observation (with my own old transparencies) that the range of EVs in a Kodachrome transparency that is transilluminated with diffuse light is less than the EV range of the typical original scene. Ektachrome--especially now that the D-max has faded---is less contrasty than the Kodachrome.
However, I will try the HDR technique next time I copy slides to see if the files so processed have a better, more pleasing look.
Keith B., Santa Monica, CA, USA

charlie

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Re: Batch processing HDR images
« Reply #6 on: December 27, 2018, 04:59:46 »
It has been my experience that the D800 (or a scanner like the epson V700) can have a hard time extracting all of the detail from a slide in one exposure. So I can see why you'd want to do the HDR thing.

There is not a batch function for HDR in Lightroom but there is a keyboard shortcut that will run the HDR function in the background, sort of a manual batch option. You can apply this to several sets of images at a time so essentially you'll be able to walk away from your computer for longer periods before coming back start more HDR process'. The shortcut is Ctrl-Shift-H, it skips the preview dialog box and will apply the last settings you used for HDR.   

Select 5 images you want to merge for HDR & press Ctrl-Shift-H, select the next 5 images to merge for HDR & press Ctrl-Shift-H, and so on. My slow old computer can handle 4 or 5 sets of HDR process' at a time before LR stops responding, a newer/stronger computer should be able to handle more at a time.

Seapy

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Re: Batch processing HDR images
« Reply #7 on: December 27, 2018, 09:43:33 »
Thank you Charlie, for confirming my approach and the tip for Lightroom, I will try it with the next batch. I have been using control-H but wasn't aware of the additional 'shift' function.  I am sure there will be something in Photoshop/Bridge which would allow an unlimited batch to be run but this is good enough, I don't expect to be doing thousands of exposures, my time is free!

I am running a 6 core 3.06Ghz Intel MacPro 5.1 with 24Gb Ram. I did freeze it with 12 D800 NEF's in one batch but on the second run it swallowed them and returned a nice image.  I do have another strip to take me to 32Gb RAM but tests have shown the computer runs faster with 24Gb because there are only 3 RAM channels, so if you fit 4 strips, 2 strips have to share 1 channel, which slows things down (a tad).

Another benefit of this exposure stacking method, I seem to see better detail in the final image than any of the individual images.  Some of the plants have name labels which in each individual image the lettering is indistinct, bitty. In the stacked HDR image the lettering is solid and clearly distinct, presumably this also extends to the rest of the image so it appears that I am also  extracting more detail from the slide by using multiple exposures.  This isn't immediately obvious because generally these images aren't the sharpest I have seen... My father didn't own a tripod.

Off to get a bigger SSD, more elbow room...  ;D    ...500Gb or 1Tb, Samsung 860EVO or Crutial MX500, decisions!  :-\  All my SSD's are 250Gb Crutial, I feel it's time to step up a gear with the D800.
Robert C. P.
South Cumbria, UK

Seapy

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Re: Batch processing HDR images
« Reply #8 on: January 07, 2019, 23:33:42 »
OK, I'm processing a batch of D800 photographs in bracketed sets of 5 with Lightroom using ctrl+shift+H combo. Lr reports number of operations in progress, in this case 3, I will try for more, but don't want to push things...

Seems faster than previous method of one at a time...

Processing 15 images of the Meikleour Beech Hedge which holds the record for the largest hedge in the World.
Robert C. P.
South Cumbria, UK

Seapy

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Re: Batch processing HDR images
« Reply #9 on: January 07, 2019, 23:49:23 »
This is the result from one of the D800 files I copied this evening, HDR from five bracketed images of a slide my father made in 1965 using a contaflex with Kodachrome.
 .
Robert C. P.
South Cumbria, UK