[MJKoski]

Mess how? I wouldn't expect any computation errors from a Bright composite, but that wouldn't prevent it from looking like a visually busy disaster.

Exactly, visual disaster

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I have tried to use the bright mode to produce "one shot" star trails. It almost works but it also amplifies white dot count if composite is made of long exposure at moderate to high ISO. Here is a bright mode composite with K-1 MK1:



Dark areas are quite busy with noise artifacts.

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Last edited by MJKoski; 10-03-2019 at 01:50 PM.

[MarkJerling]

Exactly, visual disaster

--

I have tried to use the bright mode to produce "one shot" star trails. It almost works but it also amplifies white dot count if composite is made of long exposure at moderate to high ISO. Here is a bright mode composite with K-1 MK1:



Dark areas are quite busy with noise artifacts.

Busy or not with artifacts, that's a lovely image. Well done.

[MossyRocks]

Dark areas are quite busy with noise artifacts.

Is that noise or hot pixels? I'm kind of leaning towards hot pixels given how mono channel each is

[edri]

They appear to be hot pixels.

[MJKoski]

Yes. And as the composition mode is "bright", hot pixels calculate as high intensity light and their count increments as exposures are being stacked.

[biz-engineer]

Yes. And as the composition mode is "bright", hot pixels calculate as high intensity light and their count increments as exposures are being stacked.

Remove dark frame. I used to use the LENR in camera, but that's not the best option. Before I leave the shooting location, I put the cap on the lens and trigger a dark frame exposure performed while I drive to another location or go back home, when I arrive the dark frame is available on memory card. No need to wait for that boring 15 minutes dark frame shot.

[kiwi_jono]

Oh yea, average works.

128x 3sec frame average to retain highlights AND allowing about 7 stop boost for dark areas:


60x30sec averaging


Just do not go too far or you will get this:


It is a failed 600x average due to internal buffer overflow and/or calculation precision limit. I found out that 256x is a practical limit for 0EV exposed images containing lots of mid-tones. These were taken with K-1 and K-1 mk2.

Here is about 128x 10sec average with Pentax KP:


Here is a rare example were 512x average worked (technically):


In the image, there are chunks of ice going around in circles due to water movements.

Great shots - like your style.

Sorry but I really like your failed multi exposure (but then perhaps if I looked at it in higher resolution I would not like it so much)!

[biz-engineer]

5) using "averaging" mode to stack short-shutter-time shots will have less dark current noise than the equivalent high-ND-long-shutter-time shot.

For single long exposure (2 to 4 minutes exposures) around sunset (or sunrise) the light level drops (or increases) rapidly, making it difficult to nail exposure base on the automatic exposure time evaluation before the exposure takes place. Using a weak ND filter for a multi-exposure composite average in Av mode, is a method that nails exposure of the total stack because AE metering tracks falling light level before each of the shorter exposures, so in that case the composite average mode has the advantage over a single exposure.

[MJKoski]

Traditional dark frame does not work when trying to use it with 120x30sec "bright" stack where each frame adds more and more hot pixels into the stacking function.

[photoptimist]

For single long exposure (2 to 4 minutes exposures) around sunset (or sunrise) the light level drops (or increases) rapidly, making it difficult to nail exposure base on the automatic exposure time evaluation before the exposure takes place. Using a weak ND filter for a multi-exposure composite average in Av mode, is a method that nails exposure of the total stack because AE metering tracks falling light level before each of the shorter exposures, so in that case the composite average mode has the advantage over a single exposure.

Great point!

I miss the TTL timed-exposure systems of some film cameras that kept the shutter open until they had accumulated enough light in real time after the shutter opened.

That can be emulated with interval composite set to additive mode with the "Save Process" option -- one can pick the image in the set that reached sufficient exposure without blown highlights. Of course, additive mode does accumulate dark current.


One other big advantage of interval composite is that it can show the blurred scene over a long time period without holding the shutter open the entire time and accumulate too much dark current noise. For example, 60 shots taken with a 1/100 shutter speed on a 1 minute interval provides a similar effect as a deep ND shot with a 1 hour shutter time. But the interval composite shot only has 0.6 seconds of open shutter time so the dark current is miniscule.

[biz-engineer]

That can be emulated with interval composite set to additive mode with the "Save Process" option -- one can pick the image in the set that reached sufficient exposure without blown highlights.

Yes, you can select the save option and have the intermediate stacks of the process. With "additive" + "save" you can select the raw file for which you like the exposure level best, and with "average" + "save" you can select the raw file according to how best blurred you like the clouds or water, because each additional stack saved will equate an increment in exposure time. That's a great feature.

---------- Post added 05-10-19 at 20:26 ----------

One other big advantage of interval composite is that it can show the blurred scene over a long time period without holding the shutter open the entire time

If you trigger each new exposure with a remote device, you can check in LV how the stacked frame look like before adding one more exposure up to your liking, and press the Image Review button when you want to terminate the stack. That's actually pretty good.

[gatorguy]

Busy or not with artifacts, that's a lovely image. Well done.

I agree. Absolutely worth the trade-off. It turned out really well, something I personally would be proud of.

[biz-engineer]

Traditional dark frame does not work when trying to use it with 120x30sec "bright" stack where each frame adds more and more hot pixels into the stacking function.

That's because you have to do a dummy exposure to warm up the sensor so that the temperature isn't changing much between the beginning image exposure and dark exposure at the end of the sequence. You could even do a dummy exposure time, dark frame, image sequence, dark frame again , and use the average of the two dark frame as reference to substract from your image sequence. Anyway, not 100% of the hot pixels appear systematically, some hot pixels appear at random position and for those pixels dark frame subtraction will never work. For star trails, hot pixels aren't a problem, PDCU has a spurius noise reduction slider which remove lone pixels who happened to light up in the middle of nowhere, so PDCU is one more option to deal with hot pixels for long exposures with star trails.

[Greg1956]

Very interesting.

I'm wondering whether in camera averaging would be a good solution for night time shots eg average 8 shots???

And for astrophotography. Might be worth trying next time I'm out.

Greg

[agukha]

Thank you for all those information, it makes me wanting to try this functionality to compare what it can do against long exposures.
(and by the way could be usefull on "photo marathon" I do sometimes where no retouching is allowed outside camera !! )