Low light sharpness

[botty1963]

Hi folks. I took some photos of the Northern Lights in Iceland in October, and whilst they were acceptable as memories of what we saw, I wasn't too happy with the quality due to how grainy there were. I had seen various suggestions as to what settings to use, and some contradicted others although I appreciate that a lot depends on the kit that you have available to you.

I went with my Canon 10-22 but that has 3.5 as it's max aperture so needed to adjust settings to accommodate this and this is where I think I went wrong a little. I have a Canon 7D so as this is a little old in the tooth now it's high ISO performance probably isn't that great, and I used 3200 as some suggested, but this gave me a shorter shutter speed. I think that if I had increased the shutter speed and dropped the ISO a little then I would have got sharper photos; I suppose though that with moving lights and longer shutter speed then the photos may have become a little blurry.

People had advised that it's best to head out to where there is no or little light, we founds spots in the middle of nowhere so no light pollution, but, maybe no extra light to allow the lower ISO?

Any advise would be appreciated as we go back in March.

[DanK]

Welcome to CiC. Can you please go to your profile at the top and add your name and location? We go by (real) first names here, and your location will sometimes help people give you better advice.

To get better feedback, you should post one of the photos, along with exif information.

Not having seen the photos, my guess is that the problem is a combination of high ISO and underexposure. 3200 is quite high for a 7D (I have one). When you set a higher ISO, you are not increasing the sensitivity of the sensor. You are simply telling the camera to amplify the output, and that will include the noise as well as the signal. The amplified noise will be most apparent in parts of the image that are weakly exposed.

This should be fairly easy to diagnose once you post an example.

[xpatUSA]

Hi folks. I took some photos of the Northern Lights in Iceland in October, and whilst they were acceptable as memories of what we saw, I wasn't too happy with the quality due to how grainy there were. I had seen various suggestions as to what settings to use, and some contradicted others although I appreciate that a lot depends on the kit that you have available to you.

Any advise would be appreciated as we go back in March.

If you go here and look at the noise results for the 7D; run the mouse around to see the changes.

Looks like you just missed the boat :-(

There's a big increase in noise (the grainy appearance) going from ISO 1600 to 3200. And, on another forum, it is said in technical discussion that Canon does something above ISO 1600.

Been up in the Arctic circle twice but never saw the lights. However, the lights themselves look quite blurry even on HD TV, so I'm wondering why you're seeking sharpness. But then, they do appear to jump around a bit, so I imagine you're trying to avoid motion blur.

Anyhow, the 7D looked OK-ish when comparing ISO 1600 to 100. So I would use 1600 and take many exposures perhaps with bracketing multiple times to try an capture that magic moment when they are stationary or moving slowly.

Mostly speculation on my part.

[chauncey]

Canon is not known for low light performance...my personal limit is ISO 400.
Yeah I do miss a lot of shots...c'est la vie!

[Dave Humphries]

Hi ???,

Are you shooting RAW or jpg?

If jpg, using higher ISOs will soften the images significantly.

I don't know if Canon has a 'high ISO noise reduction' feature, but that typically would become effective at that level of ISO and would help reduce the impact of noise (at the expense of waiting while it 'exposes' a dark frame of equal length to your image exposure time). Did you have that turned on?

Cheers (and welcome to the CiC forums), Dave

[tbob]

I can only speak from my experience with the northern lights. I use ISO 1600 and manual settings (Bulb, aperture 4.5 or as close to wide open as your lens will permit, manual focus to just a bit before infinity). I then shoot at anything from seven seconds to forty seconds depending on how bright the aurora is. Basically shoot for a long as it takes to make the aurora bright and not overexpose the brightest bits. Takes a bit of guessing; especially as the aurora will greally fluctuate from minute to minute.

And shoot RAW. Get as much latitude as you can.

[botty1963]

Hi folks, many thanks for the replies. I took RAW but did little with them due to the fact that I considered them too grainy to bother with, I shot at 3200, f3.5, 10mm and 2 seconds. I used manual focus and focused a tiny amount short of infinity. We were fortunate that we saw the lights on two evenings, but I think that I just wanted to make sure that I got something without really preparing. I think I need quite a but longer shutter speed next time and to drop the ISO. I may be being a little harsh with myself as you see the photos where someone has really spent some time looking for a location that adds to the photo, and spent more time preparing and later editing, and you expect the photos all to look like those.

[tbob]

Steve If these images are unprocessed then you can certainly make huge strides in post processing. These are very good, the graininess is not a problem. 99.99% of humanity will never even note the grain. Take my word for it; i can show you much grainier images I have taken.

An example; any nonphotographer I showed this was impressed. To me it was, and is, hideously grainy.

Digital noise: Horrid or just obnoxious.

[DanK]

thanks for posting the actual images. It confirms my hunch. While Trevor is right that you can do a lot with these in postprocessing, the problem is very clear: both of these images, particularly the one on the bottom, are badly underexposed, and that in combination with the high ISO are generating a lot of visible noise. Here are the histograms from your jpegs, from photoshop. The long tails on the right are just things like the tiny bright lights and can be ignored.





This underexposure will increase the amount of visible noise in any case because darker areas have less signal but the same noise. However its effects can be quite striking when you push the ISO high. We had a thread about this not long ago. The bottom line was that if you are going to shoot at a high ISO, avoid underexposure and exposure to the right.

[DanK]

Here are some test shots done with a 7D at ISO 3200.

First, here is a histogram for a 4-stop underexposure, for comparison to yours:



Yours are not SOOC, but I would say that yours are at least this severely underexposed.

First, here is the test shot properly exposed. I did nothing to this other than read it into Lightroom. You can see that at this resolution, it is quite low in noise. Check the wall, the edge of the bookcase, and the whites on the spines of the CDs.



If you want to see the full-size image, go here.

Now, here is a 3-stop underexposure, boosted by 3 stops in LR. You can clearly see the noise emerging. At this low resolution, it's not too bad, but at larger sizes, it's more noticeable. For the full-size image, go here.



Finally, here is a 4-stop underexposure, boosted by 4 stops in LR. Even at this low resolution, it's a low-quality image.



For the full-size image, go here. You can see that the image is very low quality. At a resolution larger than a computer screen, this would be a problem.

[botty1963]

Excellent comparison, I didn't realise how underexposing could have such an effect on how grainy the picture looks.