Which is better? Stacking or noise reduction?

Monday 24 July 2023, 15:30 by Nando Harmsen | 4,719 views | 15 comments

This article was translated from Dutch with the help of AI. Read the original.

Noise reduction is becoming increasingly advanced. With machine learning algorithms, it is possible to bring back details that are no longer visible because of noise. Is modern noise reduction technology better than stacking photos, or is stacking still the better method?

Not so long ago, Adobe added machine learning noise reduction to Lightroom. It is called AI, although I don't think this has anything to do with artificial intelligence at all. But that's beside the point.

As we all know, all this 'smart' noise reduction software turns out to work incredibly well. Some are better than others, or faster. But there is no denying that they all produce good results.

AI noise reduction in Luminar NEO is not free. You have to pay extra to have it available.
Another technique for reducing noise is stacking photos. This technique makes use of the random nature of noise. By stacking and combining multiple photos, you can filter out the noise.

This technique is widely used in astrophotography, both when photographing through a telescope and when photographing the Milky Way. This makes it possible to show plenty of detail despite the need for high ISO settings. The only problem is that it takes a lot of work.

AI noise reduction in Lightroom Classic can be slow, especially on an older computer.
The technique can also be used for photos taken with a drone. The small sensors in these devices are often sensitive to noise, so you can hardly raise the ISO. Even a small edit can create a lot of noise.

Stacking requires preparation and quite a bit of work. Not every subject is suitable for it.
Smartphones and some cameras even use this stacking technique to remove noise from a photo. This makes it possible to take reasonably good photos with a smartphone in the dark.

I wondered what works best. Modern AI noise reduction, or the old-fashioned method of stacking multiple photos? To find out, I stacked a few photos to remove the noise. I also edited one of those photos with the 'smart' noise reduction in Lightroom Classic and Luminar NEO.

Each noise reduction process used the following settings: Lightroom Classic at 66% strength, and Luminar NEO at the recommended noise reduction strength. In all cases, this was 'high'.

In a dark church in France. The photo was taken at ISO 25,600, so there is a lot of noise present.

A photo in a church

The photo above was taken handheld with a Canon EOS R5 at ISO 25,600. When taking the photo, I made a series of 14 exposures so I could stack them.

This and other photos of this church were used to explain the stacking method. I explained how stacking works in an article that you can find via this link.

A 100% view of part of the photo. Notice the difference in detail.
The noise is removed well from this photo. Details are preserved reasonably well, but the larger areas quickly become smeared, without any texture. Lightroom Classic manages to retain more detail than Luminar NEO. Stacking, however, produces the most detail.

A landscape at dusk, photographed with a drone. Even at ISO 100, a lot of noise has appeared. The edit was made to suit my own taste.

A photo with a drone

Drones are often sensitive to noise. That's why I almost always take a series of 5 photos in raw format, which I stack later.

This is an extra difficult situation because it was already getting dark and there was little light available. The photo was taken with a DJI Mavic Pro 2 at ISO 100 and 1.7 stops underexposure to retain the highlights.

A 100% enlargement of part of the photo shows how differently the noise reduction software handles detail.
Although AI noise reduction generally produces a reasonable result, close inspection still shows that detail has been lost. Luminar NEO performs much less well than Lightroom Classic in this respect. Stacking, on the other hand, preserves the most detail.

A photo of the Milky Way

A high ISO setting is desirable for photographing the Milky Way properly. Especially because you also have to take the movement of the stars into account. Very long shutter speeds are therefore not possible.

The Milky Way in all its glory, photographed in France. ISO 12,800 was used. Stacking a photo like this requires a lot of manual work.
This photo was taken with a Canon EOS 5D mark IV at ISO 12,800. The contrast was increased to taste to bring out the Milky Way more. The stack consists of 8 individual photos, with the rotation of the night sky corrected manually.

The 100% enlargement clearly shows the effect of AI noise reduction. Many stars are seen as noise and disappear.
Noise reduction results in a considerable loss of detail. Far fewer stars are visible and some areas are smeared too much. Lightroom Classic performs significantly better than Luminar NEO. Stacking produces the most detailed result.

A cautious conclusion

Noise reduction in Lightroom Classic and Luminar NEO generally performs well. You do need to watch out for loss of detail, which usually only becomes visible when you look critically at the details.

The price of removing noise through software, almost completely, is a smeared appearance in many cases. This gives the photo a very artificial look.

Stacking manages to preserve much more detail in all cases. At first glance, it may seem to contain a little more noise, but that slight presence of noise gives the photo more dynamism and realism.

I can't say how this works with other noise reduction software. I don't have this software available. In the case of Lightroom Classic and Luminar NEO, it is clear to me. Stacking photos produces a nicer result.

Of course, stacking is not always possible, especially with moving subjects. That's why I think AI noise reduction is and will remain very useful, as long as you use it with care.

Do you use noise reduction software? If so, which one do you use and how do you like it? Have you ever compared it extensively and critically with other software? Let us know in a comment below this post.

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About the author

Nando Harmsen has been photographing for more than 40 years. He specialises in wedding photography and landscape photography. Nando also gives talks, workshops, masterclasses and photo trips, and regularly reviews new and interesting equipment.

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15 comments

jaak wrote on Tuesday 25 July 2023 at 11:41 | reply
Personally, I now always use TOPAZ AI for things like noise reduction, and I find the results better than those from PhotoShop. No experience with LRC or Luminar.
Translated from Dutch.

Donald Willemsen wrote on Tuesday 25 July 2023 at 12:07 | reply
Nando, could you use the in-camera focus stacking of the Canon Eos R7 for stacking to reduce noise?
Translated from Dutch.

Nando wrote on Tuesday 25 July 2023 at 12:14 | reply
Focus stacking is quite different from taking a series of exactly the same photos. With focus stacking, your point of focus is different in each photo. Also, Canon does not merge the photos, you have to do that on the computer.
Translated from Dutch.

Donald Willemsen wrote on Tuesday 25 July 2023 at 13:01 | reply
Nando, then you really should inform yourself better. The Canon Eos R7 does combine the RAW files into a single photo in JPG. The only thing that is correct is that the focus is shifted for each photo. But through the settings you can influence how much the focus is shifted.
You therefore don't have to do the merging with the computer.
Translated from Dutch.

Nando wrote on Tuesday 25 July 2023 at 13:19 | reply
Then I'll take a look at that tomorrow or the day after tomorrow, because I indeed didn't know that.
But yeah, a jpeg is of course not what you want to have, and you don't have control over the exposure, merging with focus breathing and that kind of thing in the camera.
Anyway... focus stacking has nothing to do with stacking for noise reduction, at any rate.
Translated from Dutch.

Donald Willemsen wrote on Tuesday 25 July 2023 at 13:41 | reply
Nando, although the end result in the R7 is a composite photo in JPG, you still have all the RAW files that JPG was built from. You can still work on them on the computer afterwards.
Translated from Dutch.

Nando wrote on Wednesday 26 July 2023 at 20:31 | reply
I just checked the EOS R10, and indeed, depth mapping is available. I didn't know that. Unfortunately, it's not available with the EOS R5, but it is with an R50 and apparently the R7 as well. I heard that the R3 also got it via a firmware update. Then the R6II probably has it too. On the other hand, it's not much of a miss for me; I would never do that in the camera itself anyway.
It is at least a good development that this is now also available in a selection of Canon cameras.
Translated from Dutch.

guest wrote on Wednesday 26 July 2023 at 20:03 | reply
Hi Nando, interesting article. I haven't used stacking for astrophotography yet. I'm curious how you manually correct for the rotation of the night sky.
As for noise cancelling, Topaz is indeed my favorite.
Translated from Dutch.

Nando wrote on Wednesday 26 July 2023 at 20:25 | reply
That is easy to tell. Have a look at the following article on my (own) site. Reading it takes some time, actually doing it yourself takes a lot of time.
https://www.nandoonline.com/sterrenfotografie-zonder-ruis/
Translated from Dutch.

Paul eos wrote on Wednesday 26 July 2023 at 21:33 | reply
Hi Nando, do you mean that stacking doesn't work on your R5?
On my R5 it does, at least, under camera menu no. 5 =>Focus bracketing. Here you can have the camera take up to 99 photos in succession, also in raw. Then you can choose to stack them directly in your camera into one jpeg or with another stacking program. That works super well and very quickly, I do that regularly. Only the focus point between your photos has to be set somewhat by feel, but with a bit of experience you learn quickly.
Translated from Dutch.

Nando wrote on Wednesday 26 July 2023 at 23:27 | reply
I can do focus bracketing, but not merge. It's called depth mapping.
Can your R5 do depth mapping? That option isn't in the menu on mine.
That's strange. I have the latest firmware version installed, but I can only do focus stacking, not merge.
Translated from Dutch.

Paul eos wrote on Thursday 27 July 2023 at 07:54 | reply
Hi Nando, you're right because I tested it immediately. The option to merge the R5 photos in-camera indeed isn't there, I have firmware version 1.8.1.
I also have an R6 mk II and it does have the "depth composition" option to turn on or off. That's why I thought it would work on the R5 too.
I never use that depth mapping in-camera because I prefer to edit the raw files first and then merge them. In LRc that goes very quickly because you only have to edit one raw file and then you can synchronize the other raw files.
Nowadays I use c raw, it uses much less memory and I don't see any difference compared to raw format. Do you have any experience with this, perhaps discuss it in another section sometime?
Thanks in advance for your informative tips and explanation!
Translated from Dutch.

Nando wrote on Friday 28 July 2023 at 09:47 | reply
Well, luckily. Then I haven't gone completely crazy
hahaha
But at the same time it's a shame that the EOS R5 is so far behind with options added via firmware.
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Christiaan wrote on Thursday 27 July 2023 at 09:42 | reply
Maybe useful to mention explicit ISO stacking, which is therefore something different from focus stacking mentioned in the comments. The nice thing about ISO stacking is that you can also just shoot handheld. There is some difference between the images then, but Photoshop or Affinity Photo can align them well.

I've only applied it a few times myself as a test, but was pleasantly surprised by the results. Just like with focus stacking, you can't apply it to every subject, of course.
Translated from Dutch.

Nando wrote on Friday 28 July 2023 at 09:49 | reply
The term ISO stacking causes more confusion, in my opinion. It implies that photos with multiple ISO values are being combined. Just as multiple focus points are used with focus stacking.
This way of stacking is stacking exactly the same photos.
Translated from Dutch.

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