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Olympus OMD EM1 Gordon Laing, January 2014
 
 

Olympus OMD EM1 long exposure noise

  Olympus OMD EM1 results
1 Olympus OMD EM1 Quality JPEG
2 Olympus OMD EM1 Quality RAW
3 Olympus OMD EM1 Noise JPEG
4 Olympus OMD EM1 Noise RAW
5 Olympus OMD EM1 diffraction compensation
6 Olympus OMD EM1 Lumix 7-14mm flare
7 Olympus OMD EM1 long exposure noise
8 Olympus OMD EM1 Sample images
 
The Olympus OMD EM1 is very well-equipped for long exposure photography. You can manually select shutter speeds down to 60 seconds or opt for Bulb or Time modes in Manual extending as long as 30 minutes. The difference between Bulb and Time is the former keeps the shutter open while you have the release button pressed, while the latter opens it with a single press and closes it with another, so you don't need to keep the button held down throughout the entire exposure. The EM1 also lets you set maximum exposure lengths for Bulb and Time to 1, 2, 4, 8, 15, 20, 25 or 30 minutes, after which the camera will automatically end the exposure. Coupled with a delayed start using the self-timer or anti-shock option, this allows you to take long exposures without the need for a cable release accessory.

What makes the Olympus cameras even more unique though are their Live Bulb and Live Time options which let you take regular peeks at the exposure on the screen as it builds-up to see how it's getting on. This lets you stop the exposure early if it's already perfect, or perhaps not going to work out. The interval between updates can be set to 0.5, 1, 2, 4, 8, 15, 30 or 60 seconds, and the maximum number of peeks depends on the ISO value: 9, 14, 19 or 24 times for ISOs of 1600, 800, 400 or Low respectively. Once you've used up your allocation of peeks, there'll be no more, regardless of the exposure length.

The ability to take a peek at long exposures as they build is a boon in theory, but I wondered what impact it might have on noise levels, especially as the Olympus cameras impose a limit to the number of updates which decreases as the ISO increases. I'd also heard from those who owned both the EM5 and EM1 and had found long exposure noise to be worse on the new model. So on this page I'll investigate long exposure noise quality on the EM1 and compare it to the EM5 before it.

Note all tests were performed with the EM1 running firmware version 1.1 which, among other things, promises improved quality in Live Bulb mode. I also ran Pixel Mapping prior to my tests.

To show you what's possible in a real-life environment, here's a two minute exposure of Brighton Pier on the UK's South Coast, using the 17mm f1.8 lens with a LEE Big Stopper ND filter fitted. I set the camera to apply long exposure noise reduction, which takes a 'dark frame' of the same exposure length afterwards, and disabled live peeking, so this is a best-case scenario. With two minutes for the exposure and two more for the dark frame, the total time taken to capture this image was four minutes.

 

6.05MB, Time (NR enabled), 120 secs, f3.2, 100 ISO, 17mm (34mm equiv) + LEE Big Stopper

Olympus OMD EM1 sample image: 2 minutes with NR and Lee Big Stopper
Click image to access original at Flickr
 

I spent many evenings experimenting with long exposures using the EM1 and EM5 on Brighton Pier and got some useful and interesting results, but inevitably the conditions were in constant change, preventing me from making definitive comparisons. So for consistent and controlled conditions I moved indoors and photographed a still-life of a toy train under artificial light using the Olympus 45mm f1.8 lens and my LEE Big Stopper ND filter.

I experimented with different exposure times ranging from 30 seconds to two minutes with and without long exposure noise reduction enabled, and also with and without live peeking enabled. I then repeated my tests for the EM5 for direct comparison. All the exposures were made at the base sensitivity of 200 ISO, the white balance was fixed and the aperture adjusted for the different exposure times as the filter and light source remained fixed; note the aperture was wide open for the 30 second exposures, so the depth of field is shallower than the others with some slightly softer details as a result. Finally, the room was quite cold (UK winter with no heating on) and each camera was allowed one minute to cool down between exposures. Here's what I discovered.

         
Olympus OMD EM1 long exposure noise (30, 60, 120 secs at 200 ISO)
Noise Reduction On, Noise Filter Standard, Live Time disabled, 100% crops from in-camera JPEG
30 seconds, 200 ISO, NR On
60 seconds, 200 ISO, NR On
120 seconds, 200 ISO, NR On

In my first comparison above you'll see 100% crops taken from in-camera JPEGs at 30, 60 and 120 seconds with Noise Reduction enabled and the Standard Noise Filter. Enabling Noise Reduction on the EM1 for long exposures takes a second exposure of the same length immediately after the first as a 'dark frame', allowing noise to be subtracted. This is very effective technique resulting in almost noise-free images on the EM1 above, but doubles the amount of time required to record each image - so a 30 second exposure takes one minute to complete, a 60 second requires two minutes, and a 120 second requires four minutes. During the dark frame exposure the camera is locked, which may not be an issue if you're shooting cities or sea and sky-scapes in fairly static lighting conditions, but could mean missing a key explosion in a fireworks display or leaving gaps between star trails on a stacked composition. So it's important to also see how the noise compares with noise reduction turned off. I've made that comparison below.

         
Olympus OMD EM1 long exposure noise (30, 60, 120 secs at 200 ISO)
Noise Reduction Off, Noise Filter Off, Live Time disabled, 100% crops from in-camera JPEG
30 seconds, 200 ISO, NR Off
60 seconds, 200 ISO, NR Off
120 seconds, 200 ISO, NR Off

In my second comparison above you'll see 100% crops taken from in-camera JPEGs at 30, 60 and 120 seconds with Noise Reduction off and the Noise Filter also set to Off. It doesn't take a pixel-peeper to notice green speckles sprinkled over the crops, which become progressively worse as the exposure increases. Unfortunately these are hot pixels which are much harder to reduce than high ISO noise. When I put the accompanying RAW files through Adobe Camera RAW, it couldn't do anything to reduce the speckles, and any enhancements to the image actually made them more obvious; indeed I'd say the in-camera JPEG processing is doing it's best to minimise their impact.

So from this initial comparison I'd say it's best not to shoot exposures longer than 30 seconds or so on the EM1 without noise reduction applied, unless you don't mind a big serving of hot pixels. Once again though, applying noise reduction comes at the price of a delay between exposures as the dark frame is being recorded, which in turn makes it frustrating for fireworks displays or stacked star trail composites. And again I couldn't personally find a way to easily process the hot pixels out from RAW files, but I'd love to hear from anyone who can.

This also begs the question though, is the EM1 any better - or indeed any worse - than the EM5 in this regard? Find out below where I've repeated the EM1 results below the EM5 results for an easier comparison. So on the top row is the EM5 and on the bottom row is the EM1.

         
Olympus OMD EM5 top row, OMD EM1 bottom row
Long exposure noise (30, 60, 120 secs at 200 ISO)
Noise Reduction On, Noise Filter Standard, Live Time disabled, 100% crops from in-camera JPEG
EM5, 30 seconds, 200 ISO, NR On
EM5, 60 seconds, 200 ISO, NR On
EM5, 120 seconds, 200 ISO, NR On
         
EM1, 30 seconds, 200 ISO, NR On
EM1, 60 seconds, 200 ISO, NR On
EM1, 120 seconds, 200 ISO, NR On

I'll start as before with both cameras applying noise reduction with their standard noise filters. The results between them above are essentially the same: virtually noise-free at 30 seconds and only the faintest of speckles appearing at two minutes. I'd say there's nothing to choose between the EM1 and EM5 at this point. But now check below when noise reduction is turned off. Once again it's the older and cheaper EM5 on the top row and the newer and more expensive EM1 on the bottom row.

 
Olympus OMD EM5 top row, OMD EM1 bottom row
Long exposure noise (30, 60, 120 secs at 200 ISO)
Noise Reduction Off, Noise Filter Off, Live Time disabled, 100% crops from in-camera JPEG
30 seconds, 200 ISO, NR Off
60 seconds, 200 ISO, NR Off
120 seconds, 200 ISO, NR Off
         
30 seconds, 200 ISO, NR Off
60 seconds, 200 ISO, NR Off
120 seconds, 200 ISO, NR Off

In the comparison above, you're looking at 30, 60 and 120 second exposures from each camera with noise reduction disabled. On the top row it's the EM5 and on the bottom row it's the EM1, and this time the difference is clear to see. The EM1 is displaying those nasty hot pixels which get worse as the exposure lengthens, but in stark contrast the older and cheaper EM5 remains pretty clean throughout. Believe me, this is not a mistake. I repeated the tests in a variety of conditions and always found the same result. With noise reduction turned off the EM1 will exhibit hot pixels, whereas the EM5 manages to mostly avoid them. Indeed the EM5 results with NR off look almost the same as those with NR enabled. So what's going on?

The short answer is, no-one can tell me. I don't think the older EM5 has a mysteriously superior sensor for long exposures and I don't buy into the EM1's phase-detect AF pixels being at fault as the sprinkles occur across the entire image beyond the PDAF assist area. I don't think we can blame the lack of an optical low pass filter on the EM1 either as hot pixels are nothing to do with incoming light. I additionally don't think it's the JPEG engine either as the respective RAW files exhibit the same differences.

My guess is it's something going on prior to the RAW data being recorded on the EM5 - a kind of on-chip noise reduction if you like. We've certainly seen it before on some Sony cameras. So I don't think the EM5's hardware is better, but I do think its sensor is doing something different to its data before it's recorded.

Ultimately until Olympus engineers explain what's going on (and I keep asking), we're all left guessing - the only official comment I have is that Olympus recommends using the EM1 with noise reduction enabled. But while I don't think the EM5 has a superior sensor, it clearly has something in the pipeline that's more friendly to long exposure work. If you're happy to wait and apply noise reduction to long exposures, there's nothing between the two models, but if you prefer to shoot without noise reduction, then the older EM5 is by far the preferred choice. This will be important for those who assemble long star trails from multiple exposures and understandably don't want gaps between them, or equally those who don't want their camera tied-up recording dark frames during a busy fireworks display. This issue will only affect a small minority, but if you're one of them you'll want to know the facts.

 

Olympus OMD EM1 Live Time

Before concluding this page I wanted to share some more long exposure comparisons, this time for the EM1 when it's using Live Time. This is an innovative feature for Olympus cameras where you can actually peek at a long exposure while it's building to see if it's already sufficiently cooked, or indeed if you're wasting your time for some other reason. It's also great fun, reminiscent of watching a black and white print develop in an old chemical darkroom. But my question is whether enabling these peeks has a detrimental impact to the image quality, as the number of peeks becomes less for higher sensitivities and once they're used up, you won't see any more updates to your exposure.

     
Olympus OMD EM1 long exposure noise 120 secs at 200 ISO
Noise Reduction On, Noise Filter Standard, 100% crops from in-camera JPEG
120 seconds with Live Time disabled   120 seconds with Live Time, 15 'peeks' at 8 second intervals
     

In my final comparison above, you're looking at two exposures taken with the EM1, both of them lasting two minutes with noise reduction applied. The only difference is the exposure on the left had Live Time disabled, while the one on the right had it enabled with 'peeking' at eight second intervals - this provided 15 updates throughout the exposure.

As you can see, the 100% crop of the image taken with Live Time enabled (above right), exhibits some chroma noise that's absent on the one with Live Time disabled. It's a lot more discreet than the hot pixels seen earlier though and is something that's much more easily reduced in post-production on a RAW file.

I made the same comparisons at 30 and 60 seconds and found the noise levels to be similar. The impact seems to boil down to the number of peeks you make rather than the exposure length. The more times you peek at the image, the worse the noise.

To put it in perspective again though, it's not exactly terrible, just worse than the version with it disabled. Ultimately if you want the cleanest results you should shoot without Live Time, although you could of course use it to quickly nail the correct exposure for a shot, before then turning it off and shooting your 'proper' exposure with it disabled.

Hungry for more tests? How about my EM1 diffraction compensation or EM1 with Lumix 7-14mm flare?! Or if you've seen enough, check out my EM1 sample images or skip straight to my verdict!



Olympus OMD EM1 results : Quality / RAW quality / Noise / RAW Noise / 7-14mm flare / diffraction / long exposure


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