Serious noise in low light

Hi,

I finally got my KX today, and with the day off, spent a while playing with it (quite a while actually!).

While it's taking longer than I imagined to start getting better shots, I got some fun ones which I'm pleased with in the day today. This evening though I went walking in the local woods (Leasowes in Halesowen), and I'm astonished at some of the noise in the pictures. The ISO is high, but I'm used to higher ISO on my compact, and I've never seen anything like this.

I wonder if anyone has any advice please on whether this is normal, and I being over demanding, or suggestions on what settings I may have cocked up! I'e added a better daylight one, a medium one, and the final one the worst. If you download the full size last one you can see more clearly the noise.

Thanks for any suggestions, I'm hoping to learn quickly...

Steve

One in full daylight - fine
Link on picasa-web



One in lower light - some noise
Link on picasa



Link on picasa

I can't make out noise as such, although the shot looks washed out and soft. What ISO were you actually using? If on auto-ISO, using a smaller aperture in the twilight might have made the camera select ISO 6400 or even 12800. These highest ISO settings, even on the k-x, are best left as the 'last resort'. Most digital compacts don't go this high!

If you're an auto guy, set your auto ISO limits to 100-1600 and you'll probably see a vast improvement.

I must say that I don't see much noise in these pictures. The K-x is known to be great in the noise department so one shouldn't see much noise. Are these 100% crop photos? If not that may be the reason I don't see much noise. What ISO value you used?

aha - I should have done that first, I wondered how it would work. APols, I'll do that for the last one now.

Steve

Maybe I'm being dim - but speaking as a fellow K-x owner (who's quite stunned by the low level of noise, and generally excellent low-light/high-ISO capabilities of his own K-x)... I'm not sure I can quite see the noise you're referring to.

That's not to say it's not there, mind. You could be spot on (and I'm still relatively new to my K-x, and have no experience of other dSLRs - only old film SLRs, and various digital compacts).

The matter is complicated by the fact that on Picasa, when I download the last pic as suggested, it gives me an image which is 1600×1063 pixels. Clearly, that doesn't match the 4288×2848 suggested in the panel to the right of the image in Picasa - so evidently, it's hard to make an accurate judgement of what you might be seeing. All I know for sure is that I'm not seeing the original - so all bets are off!

Just out of curiousity, what mode are you shooting in - RAW or JPEG? And what file-save quality and size settings have you chosen? The JPEG compression will make a heck of a difference to artefact 'noise' - but that's not really 'noise' in the 'sensor noise' sense of the word. The K-x is renowned (according to stuff I've been reading very recently) for having very low sensor noise at high ISO, compared to the K200D, et al.

So - maybe best to start by documenting the problem better, and then see if there's a way to have the actual taken image checked/downloaded, rather than a snap-of-a-snap(-of-a-snap, possibly). Every bit of 're-JPEGging' will potentially introduce yet more noise and make comparison impossible.

It might also be helpful if you can zoom in on a particularly 'iffy' area that you think is bad, so that the experts here can judge it (and I certainly don't put myself into that category, I hasten to add!)

Good luck,

Hi,

Sorry, yes, I should have worked on the crop first. I found pixel-peeper which did the 100% crop for me, which is now below.




I think you're right Neil, I should be more thorough before asking, when I'm likely over-reacting. I bought the KX with it's low light excellence in mind, as my current fuji has great low light, and I'd miss it if I lost it, so perhaps overreacted to my first run of shots. The 6400 ISO is a high one.

Thanks for your comments.

Steve

Ok, I can see a smidge of noise now, around her chin and neck particularly - mainly in the dark areas. But considering this is an f4, 1/100th sec at ISO6400, we've got to consider that it must've been pretty gloomy! The detail in her blouse is fine, by comparison, so it's only really struggling with the really lowlight dark-area stuff, I think.

And of course, it's worth bearing in mind that given the focal length (30mm - 45mm effective - which ain't far from a 'normal' SLR's 50mm 'standard' portrait kit-lens of old days), it's not a particularly tight close-up on the subject. There's a lot of (rather interesting) background in there, isn't there! I'd be surprised if an old-school ISO6400 negative would zoom up as well as the 100% crop above, at the size it's being displayed here in the forum! I remember even ISO400 being pretty grainy!

What I'm getting at, is if you'd framed *just* the girl, at 30mm, then I figure you'd have a tough job picking out the noise at all. It'd be lost in her buttons, or the folds of cloth here and there, maybe - and virtually invisible. You only see it now, because it's on her face (and we're conditioned to process faces more acutely). I think the noise is over-emphasised because she's really probably less than 10% of the shot and you're zooming in to look at her in portrait mode, practically. Such is the wonderment of a 12 megapixel image, we can even consider doing such a thing!

We still don't know whether we're looking at a RAW image above, or a JPEG (well, obviously we on the forum are looking at a JPEG, cos you can't post the RAW here natively)... but what I mean is, we don't know what level of JPEG compression has been used. Was it one, two or three stars, in the K-x? Or did you start with a RAW and use Pixel Peeper directly on it (in which case, what level of JPEG compression was used at that stage?) It all has a bearing, potentially.

Gut feeling is, it's ok. In fact, it's ace, all things considered. I really don't think you'd even have been able to *get* that shot with your Fuji, to be honest. But - to put your mind at rest - why not do some straight side-by-side comparisons with your Fuji, in testing conditions, and see what you get. I'd be very interested to know the results too!

Regards

ISO 6400 is extremely high. The amount of noise for ISO 6400 in the above shot is in fact low.

Many compact cameras apply strong noise reduction to smooth the image - even with the lowest NR setting in some cases. Detail is lost in the process, so you're not truly getting a better image, just a crude illusion of one. Higher resolution also reveals more flaws in an image when examined at 100%.

Your K-x is superior in terms of detail capture, and the amount of noise produced is very low compared to other APS-C DSLRs, and very low compared to film of the same speed.

Noise is produced from the analogue circuitry in the camera as the sensitivity is turned up high. It's just a natural side effect and something to be accepted, just as graininess is accepted with fast film.

You can try reducing the noise further with software, but generally you do loose detail and sharpness as a result.

Your K-x is virtually performing miracles to capture that amount of detail in low light. No compact camera can compete with it in this way.

The noise in the above image is unimportant when not cropped (and it's a nice photo uncropped).

You won't see the noise on a computer or TV screen, or on a print at a normal viewing distance. You would only notice it on a poster when standing right in front of it, and what does that matter?

For portraits, you move in closer or use a longer lens - so then noise won't be a problem.

Noise can be a real problem for things like paparazzi photography that needs heavy cropping when you can't get any closer to your subject - but that's a different and difficult subject. You often see very grainy pictures in the newspapers, often taken with some of the best cameras in the world. There's a limit to everything.

For lower-noise shots, use brighter daylight when you can, or flash. Turn down the ISO when the shutter speed would still be fast enough to freeze movement. And, when appropriate, get in close to your subject so you don't have to crop too much.

Thanks guys, that's all helpful to hear, and perhaps I need to rethink what I mean by noise, and the different levels of detail available compared to my previous cameras.

Either way, it's good to hear that's it's working as it should, and I'll loo forward to figuring out more about it. Thanks for taking the time to reassure me.

Cheers,
Steve

From my experience with taking a lot of shots in the dark with the Kx (the whole reason I bought the Kx and joined Pentax!), you will see some noise at ISO 3200 if you squint or zoom to 100%, and significant amounts at ISO 6400 (but still usable provided you don't mind a soft image). ISO 1600 is almost perfect in most low-light scenarios, 3200 is fine when shooting outdoors in the dark as long as you don't mind compromises, 6400 - at this point, you should be considering a faster lens or more light!


Also don't bother with the "Expanded ISO" mode, it makes things worse, even when not shooting at the "new" ISO 12800 or 100 modes. Awful electronic processing in-camera, nasty nasty stuff. Avoid. Switch off, do not touch. Did I say its horrible?


Personally, I now shoot mostly at ISO 400 (fixed) because that gives the widest dynamic range, and by shooting RAW and under-exposing then lifting in Lightroom, its amazing what the Kx will pull out of seeming black holes and shadows. But this is a method that's no use if you just want to press a button and get a perfect picture, of course.