Live time black dots

[birdboy]

Does anyone use live time and what sort of results do you get.

I have been getting black dots akin to dead pixels in the shadows with my OM1. Now I would assume that live time is mainly used in very low light conditions, fireworks light trials night shoots etc. I can repeat the problem at will. The black dots are not random but specific pixels. You will need to pixel peep to see these black dots but they do seriously degrade the IQ of the picture so it should be an issue.

It seems that at least one other OM5 user has experienced the black dots, so is this an issue with the new sensor and the live time feature.

I have an issue raised with Olympus technical support but am getting nowhere, they keep putting it down to noise artefacts which it is not because the black dots are in specific pixel locations.

Anyone with examples of live time shots?
Thanks John

ps Ian is their any chance that you could you your influence with the powers that be to look into this. My experience is that the problem is easily to repeat so their should be no problem confirming if this is an issue or not.

[photo_owl]

Re: Live time black dots

I'll see what I can do - but from my understanding of your previous post what we are really looking at is "what's the camera doing differently when shooting LT and bulb?"

then whatever that difference is must, in some way, be delivering those black dots.

are we on the same wavelength?

btw why should they be specific to the shadows? the only logic I can see relevant to this would be that they are mapped pixels and that the interpolation isn't done on the final rendering of the image ie the surrounding pixels are dark, the mapped ones interpolated black then subsequently there is light delivered to the area but the mapped areas stay black.....probably overthinking this!

[jmunkki]

Re: Live time black dots

It's likely that the camera is taking multiple shorter exposures and then either applying noise reduction on the sum of those exposures or on individual exposures that are accumulated into a single longer one. Or maybe they aren't applying noise reduction when live bulb mode is used?

I don't see this as a sensor issue that Olympus could fix in production (unless there's a huge sensor tech breakthrough). Could they do better with the noise reduction? Possibly/probably. I wouldn't be surprised if they could improve image quality in live bulb mode with a firmware update to make the noise reduction more accurate.

If you want to understand the behavior, I would try to test and see if the black pixels you see correspond to hot or cold pixels on the sensor. If they are hot pixels, then the noise reduction is overcompensating in live bulb mode. If they are cold pixels, then the noise reduction isn't compensating enough.

http://www.cyanogen.com/help/maximdl/Dark_Frame_Calibration.htm

[andym]

Re: Live time black dots

As it's crap weather and I'm bored and still have a cold, thought I'd have a play.Not used live time before so I might also learn something.

This is f8,9.8second exposure using Livetime, ISO1600 at 60mm on the 12-60.

Just resized


Centre crop


Top LHS crop


No other PP. Sorry but I can't see anything amiss. I still think you may have a sensor issue.

Ps exif intact also

PPS noise reduction turned off so no dark frame subtraction.

[jmunkki]

Re: Live time black dots

I think birdboy only had a problem where near-dark pixels (black sky) went completely black. Andym's test photos don't have much black in them - they look great though.

[birdboy]

Re: Live time black dots

I'll see what I can do - but from my understanding of your previous post what we are really looking at is "what's the camera doing differently when shooting LT and bulb?"

then whatever that difference is must, in some way, be delivering those black dots.

are we on the same wavelength?

btw why should they be specific to the shadows? the only logic I can see relevant to this would be that they are mapped pixels and that the interpolation isn't done on the final rendering of the image ie the surrounding pixels are dark, the mapped ones interpolated black then subsequently there is light delivered to the area but the mapped areas stay black.....probably overthinking this!

Thanks I haven't tried bulb but dialled in shutter speed and I can see a difference.

I think the dots in the shadows must relate to the intensity of the light in the photocell and the threshold that gives it an output that the camera can work on for its picture processing if that makes any sense. I get the black dots with raw files so I would not expect in camera processing to any difference.

In order to see this effect it is really important that your picture contains shadowed areas of lower light intensity, hence it really shows up in night exposures and fireworks.

[birdboy]

Re: Live time black dots

It's likely that the camera is taking multiple shorter exposures and then either applying noise reduction on the sum of those exposures or on individual exposures that are accumulated into a single longer one. Or maybe they aren't applying noise reduction when live bulb mode is used?

I don't see this as a sensor issue that Olympus could fix in production (unless there's a huge sensor tech breakthrough). Could they do better with the noise reduction? Possibly/probably. I wouldn't be surprised if they could improve image quality in live bulb mode with a firmware update to make the noise reduction more accurate.

If you want to understand the behavior, I would try to test and see if the black pixels you see correspond to hot or cold pixels on the sensor. If they are hot pixels, then the noise reduction is overcompensating in live bulb mode. If they are cold pixels, then the noise reduction isn't compensating enough.

http://www.cyanogen.com/help/maximdl...alibration.htm

As I understand Olympus's own information these black dots are not hot pixels that is another issue see the following

http://www.olympusamerica.com/crm/on..._oly_03_09.asp

[andym]

Re: Live time black dots

It did occur to me that this might occur more in shadow areas so I tried this.

[birdboy]

Re: Live time black dots

As it's crap weather and I'm bored and still have a cold, thought I'd have a play.Not used live time before so I might also learn something.

This is f8,9.8second exposure using Livetime, ISO1600 at 60mm on the 12-60.

Just resized


Centre crop


Top LHS crop


No other PP. Sorry but I can't see anything amiss. I still think you may have a sensor issue.

Ps exif intact also

PPS noise reduction turned off so no dark frame subtraction.

As has already bee pointed out I would not expect to see the black dot effect in these pictures because the expose is evenly lit.

I was really hoping that folk may have so examples of trying to use live time for night shots or light trails (but not stair trails)

But thanks for your interest and testing Andy

[birdboy]

Re: Live time black dots

It did occur to me that this might occur more in shadow areas so I tried this.

[/img][/url]

It is very specific areas of the picture where this manifests itself. Such as this



Andy any chance of pm that picture for me to have a look. Thanks John

[andym]

Re: Live time black dots

Hmmm, I've had a play but not sure how to connect a full size image to a PM if that's possible.

If not PM me an email address and I'll send you a full size copy.

[photo_owl]

Re: Live time black dots

As I understand Olympus's own information these black dots are not hot pixels that is another issue see the following
http://www.olympusamerica.com/crm/on..._oly_03_09.asp

I think you are missing what jmunkki is saying

what you are experiencing probably has it's root in hot or cold pixels, but it's not simply their impact in normal shooting - effectively as Andy's illustrated here and you have seen for yourself with the timer shot.

Livetime is creating it's image a whole different way (the display frequency is shown in the menu and differs for different ISO settings - which also seems to tie in with your stated beliefs re sensitivity and dark areas) - but what other processes are affected in the final image presentation using Livetime are unknown (as per my original post). It's in there you will find your answers - but even Oly will probably have to dig!

The more I play with it the more I don't think it's really creating the image differently, only the display element whilst shooting. There may be an impact on the system as a whole to both record and display the image at the same time ie working harder, but that's about all.

[birdboy]

Re: Live time black dots

Hmmm, I've had a play but not sure how to connect a full size image to a PM if that's possible.

If not PM me an email address and I'll send you a full size copy.

Thanks Andy got your attachments the raw file clearly shows the black dots.



Not sure what jpg settings you were using but could not see them in your jpg

I use LSF for jpgs.

[andym]

Re: Live time black dots

I'm a little baffled with the image you sent me. The black dots seem to get worse the further to the left you go.
Along the RHS apart from the very bottom I can not see them at all, for example.

Crop above the tree line in the centre


Crop above the trees above the tree line


To my old eyes they fairly close in brightness.

Draw you own conclusions but I would expect them both to have the dots if its the processing Livetime does.

[andym]

Re: Live time black dots

Right here you go.

Same crop as your more or less processed my normal way ie Converted to a full size jpeg in Silkypix and then resized in Elements 10.


Don't use Viewer but this is processed through it.



Look at those dots.

Curiouser and curiouser