14 replies to this topic

[N3p]

I am trying to see the light on something, it seems like I've hit a brick wall already.

 

It's about taking a shot of the top of the trees with some stars above.

 

A. With my camera, if I take a picture of the top of some trees and the stars, on a fixed tripod, the stars are elongated of course but much more than I could have imagined, the image is simply not usable. The top of the trees is nice, great focus, but the stars are ruining the shot. I did this using 1600 ISO / F5.6 and 15 seconds of exposition. The widest aperture I get with my EOS t7 is 4.5 or 4.8, something like that. But then again, from what I observe and using various exposures and apertures, it's probably not even possible to have an even depth of field between the trees and the stars using aperture F5.6... (Guessing for the moment)

 

B. If I install my camera on my EQ5 mount, the stars should be pinpoint but the top of the trees should be blurry (I haven't tried it yet because I know what to expect already and an attempt at dodging the pain)

 

***

Do you ask yourself if you want to have better looking landscape or better looking stars before you do a shot of both or this problem can be partially solved with expensive equipments?  I am looking at some decent landscape with star pictures and often the stars are not totally pinpoint as we see in good astrophotos, for instance, made with an unobstructed telescope, the stars are often very pinpoint.

 

Just checking for the fun of it really, mixing landscapes and stars, not too obvious.

Edited by N3p, 27 May 2024 - 04:38 PM.

[t-ara-fan]

A picture is worth 1,000 words.

 

And most importantly, what focal length are you using?  Do you know the "rule of 300" which people with low standards call the "rule of 500"?

[N3p]

A picture is worth 1,000 words.

 

And most importantly, what focal length are you using?  Do you know the "rule of 300" which people with low standards call the "rule of 500"?

Oups.. I was using 55mm of focal length on the zoom objective.. don't tell me, it's the same thing as with the telescope? With more power the objects get out of the FOV much faster...  I hadn't noticed... the FL.

 

This is my image.

 

 

And version 2 where I repaired the stars manually in Gimp but it's time consuming, fortunately there weren't many stars in this photo.. (Just like naked eyes with the light pollution) There is also a lot of noise with ISO 1600.

 

Edited by N3p, 27 May 2024 - 05:44 PM.

[whwang]

This is a very standard astro-landscape problem.  There are at least three possibilities:

 

1. The standard solution is to use a tracker (like your EQ5) to take a long-exposure image for the stars.  Before or after that immediately, turn off the tracker and take a long exposure image for the landscape.  Then you blend the two images (in Photoshop or any programs you like) to get both sharp stars and sharp landscape.
2. If you don't have a tracker, you can take many short exposures on a fixed tripod.  Then you stack the sky (with registration on stars) and landscape (no registration) separately, and blend them.  The S/N will be lower this way than method #1 if the total exposure times are the same, but you can get good results even with apertures of F4 or F5.  
3. Some trackers (like Vixen's) have a 1/2 speed mode.  With this, you can double the exposure time of a sub that does not blur the stars nor the landscape.  People don't use this method often, as just doubling the exposure time doesn't really lead to high enough S/N.  But if you don't want to do any stacking and blending and you want just one single shot, this is the method.

I use method #2 most of the time, as I don't like to carry a tracker with me when I travel.  But if I do have a tracker, method #1 gives the best possible results.  

 

This is a picture taken with method #2:

https://www.flickr.c.../in/dateposted/

The trees look a bit blurry because of the diffuse filter, not because of sky motion.  And it was taken at F4.

 

This one is even more extreme:

https://www.flickr.c.../in/dateposted/

It was taken at F5.6.

 

Cheers,

Wei-Hao

[N3p]

This is a very standard astro-landscape problem.  There are at least three possibilities:

 

1. The standard solution is to use a tracker (like your EQ5) to take a long-exposure image for the stars.  Before or after that immediately, turn off the tracker and take a long exposure image for the landscape.  Then you blend the two images (in Photoshop or any programs you like) to get both sharp stars and sharp landscape.
2. If you don't have a tracker, you can take many short exposures on a fixed tripod.  Then you stack the sky (with registration on stars) and landscape (no registration) separately, and blend them.  The S/N will be lower this way than method #1 if the total exposure times are the same, but you can get good results even with apertures of F4 or F5.  
3. Some trackers (like Vixen's) have a 1/2 speed mode.  With this, you can double the exposure time of a sub that does not blur the stars nor the landscape.  People don't use this method often, as just doubling the exposure time doesn't really lead to high enough S/N.  But if you don't want to do any stacking and blending and you want just one single shot, this is the method.

I use method #2 most of the time, as I don't like to carry a tracker with me when I travel.  But if I do have a tracker, method #1 gives the best possible results.  

 

This is a picture taken with method #2:

https://www.flickr.c.../in/dateposted/

The trees look a bit blurry because of the diffuse filter, not because of sky motion.  And it was taken at F4.

 

This one is even more extreme:

https://www.flickr.c.../in/dateposted/

It was taken at F5.6.

 

Cheers,

Wei-Hao

Thanks for the information it's interesting (method #1). I looked at a video during the weekend where the guy was blending 2 images with a scene facing the sun and underexposed landscape. He was using Photoshop, I have Gimp. It looked a bit complicated to do at first.. but I learned how to use masks in Darktable in about 1 hour. 

 

- In your opinion, how much formation is required to be able to blend images and to adjust them efficiently on Gimp?

- Can it be done with Gimp? (I think so) 

- And do you have a favorite video tutorial with gimp? (or it might be with Photoshop too.., I ask because most tutorial are not teaching exactly the right thing)

 

I'll search for it myself but I ask just in case. 

 

***

The pictures are cool, the one in the middle of the woods with the stars, the atmosphere is dark and nice, I really like it! 

 

Thanks for sharing these and for the info on Blending. 

[whwang]

Hi,

 

I use Photoshop layers for blending.  I have absolutely no experience on Gimp.  I heard it is quite capable, but I can't confirm. 

 

If you search around, you should be able to find some tutorial on how to blend the sky and foreground exposures.  I developed my own method, so I don't know what tutorials are actually available.  But I believe there should be some.

 

Sorry that I can't be more helpful.

 

Cheers,

Wei-Hao

[erictheastrojunkie]

I (and my wife) do extensive tracked landscape/nightscape panoramas, we use small tracking mounts to do tracked sky shots, then switch off the mount and do untracked foreground shots (consecutively, one after another, with no time gaps in between like many people do with daytime/blue hour composites). I teach people that for maximum image quality it's best to use a tracking/equatorial mount of some kind so you can take longer exposures of the sky using optimal camera/lens settings in order to get high signal to noise ratio while reducing the effects of aberrations caused by the optics. This of course causes the landscape to be blurred so you have to take a separate non-tracked foreground shot. You then layer the two shots in Photoshop, do a mask on the untracked foreground and blend in the tracked shot of the sky. Trees are a nightmare, avoid them at all costs, although Photoshop's sky replacement tool and masking/smart selection tools have gotten a lot better in this regard recently. 

 

You can see a whole bunch of our nightscape stuff here:

https://www.utahastr...com/nightscapes

 

A place like Yellowstone is among the hardest to do this technique, especially if you are imaging near geysers, not only do you have complex editing tasks like masking foreground trees, but you also have a lot of steam which tends to exacerbate optical problems (like LoCA) AND is a constantly changing element which can make blending the foreground with the sky look natural. 

[N3p]

Hi,

 

I use Photoshop layers for blending.  I have absolutely no experience on Gimp.  I heard it is quite capable, but I can't confirm. 

 

If you search around, you should be able to find some tutorial on how to blend the sky and foreground exposures.  I developed my own method, so I don't know what tutorials are actually available.  But I believe there should be some.

 

Sorry that I can't be more helpful.

 

Cheers,

Wei-Hao

I will check it out and find the right things, thanks.

 

 

I (and my wife) do extensive tracked landscape/nightscape panoramas, we use small tracking mounts to do tracked sky shots, then switch off the mount and do untracked foreground shots (consecutively, one after another, with no time gaps in between like many people do with daytime/blue hour composites). I teach people that for maximum image quality it's best to use a tracking/equatorial mount of some kind so you can take longer exposures of the sky using optimal camera/lens settings in order to get high signal to noise ratio while reducing the effects of aberrations caused by the optics. This of course causes the landscape to be blurred so you have to take a separate non-tracked foreground shot. You then layer the two shots in Photoshop, do a mask on the untracked foreground and blend in the tracked shot of the sky. Trees are a nightmare, avoid them at all costs, although Photoshop's sky replacement tool and masking/smart selection tools have gotten a lot better in this regard recently. 

 

You can see a whole bunch of our nightscape stuff here:

https://www.utahastr...com/nightscapes

 

A place like Yellowstone is among the hardest to do this technique, especially if you are imaging near geysers, not only do you have complex editing tasks like masking foreground trees, but you also have a lot of steam which tends to exacerbate optical problems (like LoCA) AND is a constantly changing element which can make blending the foreground with the sky look natural. 

Hello!

 

RED: This is what I thought exactly.

Purple: I will check it out this week, how to do it on GIMP, my EQ5 is not ready yet to install the camera but soon.

Green: Oh no... but I know what you mean exactly

Cyan: I'll wait for the geysers hahaha.

 

Your pictures are absolutely fantastic, I am looking at them now and enjoying very much!
 

 

[whwang]

Eric mentioned a very good point.  The sky and landscape got to be taken at the same time (consecutively).  Some people take landscape in day time or blue hours.  That's an absolutely terrible idea.  The light qualities in day and night times are very different.  Blending exposures of such large different light quality and thinking that this leads to nice pictures is just a proof that these photographers never really appreciate the scene by their own eyes.

[N3p]

Eric mentioned a very good point.  The sky and landscape got to be taken at the same time (consecutively).  Some people take landscape in day time or blue hours.  That's an absolutely terrible idea.  The light qualities in day and night times are very different.  Blending exposures of such large different light quality and thinking that this leads to nice pictures is just a proof that these photographers never really appreciate the scene by their own eyes.

Yes I agree and I can see why in this video bellow, he is working with 2 images captured consecutively, underexposed, overexposed. And from what I understand, with a cheaper camera it's better to work with 3 pictures, adding the normal exposure along with the 2 previous images.

 

He is using so many tools to adjust the blended images it's really fantastic, I hardly can't believe my eyes and the amount of available options, it's intimidating.

 

It's the first time I really look at skilled people working with GIMP.

 

https://www.youtube....h?v=R-K17wUDLAQ

[vidrazor]

I am trying to see the light on something, it seems like I've hit a brick wall already.

It's about taking a shot of the top of the trees with some stars above.

A. With my camera, if I take a picture of the top of some trees and the stars, on a fixed tripod, the stars are elongated of course but much more than I could have imagined, the image is simply not usable. The top of the trees is nice, great focus, but the stars are ruining the shot. I did this using 1600 ISO / F5.6 and 15 seconds of exposition. The widest aperture I get with my EOS t7 is 4.5 or 4.8, something like that. But then again, from what I observe and using various exposures and apertures, it's probably not even possible to have an even depth of field between the trees and the stars using aperture F5.6... (Guessing for the moment)

If you want to shoot with a fixed tripod, without having to do a composite, try Ian Norman's shutter time calculator. It will show you the longest possible time you can expose on a fixed tripod with a given lens, a given sensor size and pixel pitch, a given declination, and to what degree of precision you desire. You can then shoot your shot at those settings and you will get a sharp image of stars.

 

The caveats are declination (you're shooting pretty low, therefore fastest movement), and how much, if any, movement you can tolerate.

So try his calculator out and fire off some frames and see if you like what you get. You will probably need to do some hoop jumping in RAW data processing and noise reduction to get a satisfactory result. Instead of GIMP, I suggest working in the free open source RawTherapee or darktable. I'm not too familiar with darktable, but RawTherapee has excellent noise reduction and sharpening tools, both using wavelets, as well as additional deconvolution processes. I know GIMP has some good tools for such, but I think RawTherapee (or DarkTable) have better tools for RAW data processing.

Edited by vidrazor, 29 May 2024 - 11:55 PM.

[KLWalsh]

A picture is worth 1,000 words.

And most importantly, what focal length are you using? Do you know the "rule of 300" which people with low standards call the "rule of 500"?

LOL
‘The rule of 500’ or ‘the rule of 300’ has nothing to do with high or low standards.
Each is a ‘rule of thumb’ for Full Frame or APS-C size sensors. This has been discussed extensively.
Neither is a ‘law’. They’re simply guidelines for fixed-tripod starscape photos, to minimize the ‘ovalness’ of stars when seen (for example) on laptop screens.

[mattbarber]

Nico, whose channel on YouTube is called Nebula Photos, has done several tutorials for shooting methods and processing with free programs such as GIMP.  "Part 2a" shows how to process with GIMP, but Part 1 is how to capture the images:

 

1.  https://www.youtube....h?v=iuMZG-SyDCU

 

2a.  https://www.youtube....h?v=4_a8XmC6H3I

 

These were, I think, among Nico's early videos, but I generally find him to be more clear and articulate than many other tutors on these subjects.  He has many other videos as well on other methods of capture and processing.

[Starry_Spruce]

https://photographyl...-image-stacking

 

^ this is a good and basic intro comparing tracking vs stacking. I'm not very experienced in it, but the suggestion is that stacking, when done with the right software, can actually lead to better results (or at least more easily) than tracking when the foreground is heavily tree laden. The issue with tracking and trees is that your tracked sky image will have a large area that is a tree ghost, so even with masking it's hard to get the crisp line between tree and sky. There are probably tricks I am not aware of, but when stacking images with the right software it takes care of this alignment issue for you.

 

here is a demonstration stacking using sequator:

https://www.youtube....h?v=ODMMVrL8OrI

[N3p]

Thanks for the extra info, I worked on more basic things during the last week such as leaning how to use various setting in darktable, such as adjusting the exposure and colors of my pictures. I will jump in the current subject here later, I have others issues to solve with exposure before.

 

I will come back here a bit later.