Looking for some advice on star trails output from layering in PS

[AdrianFingleton56]

Hi,

I'm very much a novice in this area but I understand the basic principles of capturing star trail shots and have watched several YouTube videos to 'get the idea'. What I have done is take about 40-50 10 second shots of a landmark using the interval shooting feature on my Canon R7. Then I have imported these shots into Photoshop by...

1. File - Scripts - Load files into stack

2. I bring in all the layers and having selected them I change the Blend mode to 'Lighten'.

3. I hit Command+E on my Macbook Pro to get a file that I can export.

So far, so good. But when I try to export this file (in whatever format - and, btw, should I choose JPG?) I seem to get strange 'watermark' type backdrops in the sky (see posted image). Would anyone be able to suggest why this is happening, or are there some setting(s) I could change to get rid of this? There's not much point in my 'harvesting' multiple images if, when I combine them, I get this effect. And on my previous attempts to do this on a creaking Macbook Air I don't remember having this issue.

The settings on the individual images (one example below) that I combined to create the star trail were 10 second exposure, F3.5, 18mm (on a crop sensor camera, so effective 27mm) and ISO set at 3200. Thanks in advance for any suggestions. I'm shooting in RAW and obviously I used a tripod.

PS Could it be the clouds that were annoyingly 'passing over' (see single image example) that coalesced into that 'watermark' type background?





Observe odd 'watermark' type effect in sky.





One image from series as an example.



--
Adrian Fingleton

 

[W5JCK]

First off, are you stacking JPEGS? If so, then crap in will equal crap out. Convert your raw camera files to 16-bit TIFF and stack them as shown below.

The weird marks could be a file you accidentally included in the stack. Verify the stack has only the files that you want to stack.

You will do much better as far as image quality if you use a fast lens and then stop it down one or two full stops. For example, a f/1.4 stopped down to f/2 or f/2.8.

Here are the instructions I use to stack in PS:

1. File > Scripts > Load Files into Stack…
   • Leave unchecked Attempt to Automatically Align Source Images option
   • Leave unchecked Create Smart Object option
2. Select > All Layers
3. Layer > Smart Objects > Convert to Smart Object
4. Layer > Smart Objects > Stack Mode > Maximum option.

Afterwards I save the file as a PSD. BTW, if you have too big of a file it might not save. So I rasterize the layer containing the smart object of the stack, then save. You can then do any post processing. Afterwards you can save as JPEG or whatever other file type you desire.

--
Best Regards,
Jack
YouTube channel: https://www.youtube.com/channel/UCAfQN-Ygh9z7qqUXdZWM-1Q
Flickr Meteor Album: https://www.flickr.com/photos/jackswinden/albums/72157710069567721
Sony RX100M3, a6000, and a7

 

[AdrianFingleton56]

Thanks Jack - I had been stacking raw files, not jpegs. Two questions...

1. Where would you suggest I convert the raw files I plan to stack into TIFFs?

2. What does 'rasterise' mean?

Thanks again.

 

[Sittatunga]

Thanks Jack - I had been stacking raw files, not jpegs. Two questions...

1. Where would you suggest I convert the raw files I plan to stack into TIFFs?

2. What does 'rasterise' mean?

Thanks again.

You could use Canon's free DPP4 to batch process and export your .cr3 files to 16 bit TIFF - it's reputedly much faster under Windows, but a batch run gives you time for a coffee while you're waiting.

Is there a particular reason for doing this in Photoshop? StarStax (free download) (EDIT not Sequator, I misremembered, though Sequator will also do trails) is much simpler to use and has more tools such as gap filling, and it even works on a Mac.

When it comes to taking the images, I use continuous drive, 30 second exposures at ISO 200-400 with a remote release locked down for an hour or so rather than program an interval timer. That gives me a third of the number of images to stack than 10 second exposures and the lower ISO gives better colours and dynamic range. Sequator doesn't accept RAW files but will accept 16 bit TIFFs, though it outputs as 8 bit TIF (or jpeg if you don't want to tart up the final image, spot out stuck pixels etc.)

Your image is too blue for my taste, daylight white balance looks more natural, specially when you consider that something like 90% of the stars in the universe are smaller and redder than our sun.

 

[W5JCK]

Thanks Jack - I had been stacking raw files, not jpegs. Two questions...

1. Where would you suggest I convert the raw files I plan to stack into TIFFs?

2. What does 'rasterise' mean?

Thanks again.

Lightroom will also allow you to batch convert your camera raw files to 16-bit TIFFs. You can do it in PS one by one, and I wouldn't be surprised if there is a way to batch the process, so maybe do an internet search. I don't think PS will allow you to stack raw camera files though, so that is why I suggest converting them to TIFF or DNG because they will contain a much higher level of image information than JPEGs. Sony cameras come with an app to convert their Sony RAW to DNG, so maybe Canon has an app as well.

There is another freeware app called StarStaX that can stack, and it uses the same algorithms as PS, but it will only save in 8-bit rather than 16-bit. That is why I suggested using PS. I'm not familiar with Sequator, other than by name as I've never used it, but it likely only does what PS does. Most of the apps that stack use the same algorithms, but you can try it out. I've never had any issues with gaps in stacking with PS or StarStaX, but the key is to use no more than a 1 sec interval between shots. Both apps can easily fill in those short gaps if you select the proper settings. Photoshop will allow you to save the file as a PSD though, which means you can use that file to make non-destructive edits, then export it to a JPEG for the internet, or into any file format supported.

--
Best Regards,
Jack
YouTube channel: https://www.youtube.com/channel/UCAfQN-Ygh9z7qqUXdZWM-1Q
Flickr Meteor Album: https://www.flickr.com/photos/jackswinden/albums/72157710069567721
Sony RX100M3, a6000, and a7

 

[nighthiker]

Hi!

I get a similar pattern when I'm using the option 'lens correction' ON in ACR and stacking the images afterwards in PS. It's the sub-option for the 'Distortion Correction' which is responsible for it. Have you used that option and can you turn it off for a test?

 

[AdrianFingleton56]

I can try any test, and I probably should know this, but what does ACR stand for? Thanks for the suggestion

 

[mclewis]

but what does ACR stand for?

Adobe Camera Raw. It is the plugin Photoshop uses to open raw files.

 

[nighthiker]

but what does ACR stand for?

Adobe Camera Raw. It is the plugin Photoshop uses to open raw files.

Correct!

In any way: Try to avoid any re-gridding of your original image. By distortion correction, crop or whatsoever.

 

[AdrianFingleton56]

OK, I'm trying various things and trying to take on board this advice. Here's one interesting thing I have discovered. If I take 25 Canon Raw CR3 files straight off the SD card into PS (no adjusting at all), stack them, select all 25 and go 'lighten' I get a decent MOIRE-FREE star trail. I can do a screen grab of it, no visible Moire. However, if I go CMD-E to consolidate into one image OR just go straight to Export after 'lighten', any option I select brings Moire with it. Is there something I can turn off in the export process to evade this happening?

I will continue to look at other suggestions, but thought it worth pointing out the above.