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[mmalik]

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[mmalik]

Some clarification and tests I have conducted of 6D's little known feature, Multiple LENRs:


Note: All you need to do is to turn LENR 'ON'...


IMPORTANT: There is a bit misleading feature called 'Multiple exposure'; this feature does 'NOT' need to be enabled; enabling it will combine multiple exposures into one!


I tested with a Canon Timer Remote Control [TC-80N3] with following settings:


Self:...........5 sec
Interval:....5 sec
Long:.........5 min, 3 sec
Frames: As described below... numbers signify the frame numbers defined


Algorithm looks like following per Timer Remote Control settings defined above:


Note: 'Discard' is just a by-product of the multiple LENR sequence and may vary if your timer remote control settings are different from above!

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[HeyJP]

So I just took my 6D, turned on LENR, turned on mirror lock, set 2s self-timer, manual mode with 5s exposure, then used the MagicLantern Intervalometer loaded into my 6D. The intervelometer was set for 10 images with 1 image every 20 seconds.

Here's the sequence I got:

Mirror up (2 sec delay)
Shutter open (5 sec)
Dark Frame (5 sec)
calculation time (1 sec)
Image appeared for review (4 sec)
intervalometer countdown (3 sec)
Start over

So my experience was 10 images of 5s each with a 5s dark captured and subtracted for each image.

I then turned on Multiple Exposures set for 9 images using Averaging.

Repeated the above... and I ended up with a single image that had 9 images averaged, each of 5s exposure with a 5s dark subtracted.

Summary:
Using the built-in MagicLantern Intervalometer, if LENR is turned on, I get an equal length dark subtracted from each light. If Multiple Exposures enabled, I get a single image averaged with frames that each have an equal dark subtracted.

Very different than what you got with the external intervalometer.

Jim

[mmalik]

So my experience was 10 images of 5s each with a 5s dark captured and subtracted for each image.

Jim, to confirm, are you saying Multiple LENRs did NOT work with MagicLantern?


All, let's coin the term Multiple LENRs for the feature where one dark is subtracted from multiple lights to better convey the meaning and differentiate it from the term 'Multiple Exposures'? Regards

[HeyJP]

No. With MagicLantern intervalometer, for any number of frames: a new dark is created and subtracted from each light. 10 frames: 10 lights and 10 darks created with the dark subtracted from the most recent light.

For canon Multiple Exposure feature: If you set up max of 9 averages with LENR turned on... It takes 9 sets of light-dark pairs, subtracts the dark from the light and averages the 9 into 1.

Jim

[HeyJP]

Sounds like you got: LLLD LLLD LLLD with a dark generated after every 3rd light and subtracted from each of the 3 previous lights.

I got: LDLDLDLD with a dark generated after each light and subtracted from that one.

Jim

[austin.grant]

The Multiple Exposure feature seems like a point of massive headaches and image corruption. Unless polar alignment is PERFECT and stars don't move a single pixel between frames, the averaged image is going to be blurred. Remember, it's not stacking based on stars like we do in a normal workflow, it's just stacking based on the sensor and then averaging them.

[mmalik]

I got: LDLDLDLD with a dark generated after each light and subtracted from that one.

Jim, that's what I was saying above; that sequence is NOT multiple LENRs. That means MagicLantern does NOT work with native Multiple LENRs. That is simply 'Legacy LENR' (another 'suggested' term to refer to it and differentiate between the two?). Regards

[mmalik]

The Multiple Exposure feature seems like a point of massive headaches and image corruption. Unless polar alignment is PERFECT and stars don't move a single pixel between frames, the averaged image is going to be blurred. Remember, it's not stacking based on stars like we do in a normal workflow, it's just stacking based on the sensor and then averaging them.

That's correct, 'Multiple Exposures' for the most part is useless for AP. I have tested it and concur with Austin. Regards

[HeyJP]

I've used multi-exposure for doing flats to test a configuration for vignetting. That works perfect. You can knock off 9 averages quick with no stacking necessary. And you could use it for darks: 9 at a time.

But for anything else, not an astro feature.

Jim

[mmalik]

An important and relevant discovery... by Ralph...
 
 

I just read, in Alan Dyer's iBook "How to Photograph and Process Nightscapes and Timelapses," that you can extend this to four light frames for the 6D and 5D Mark III, and five for the 5D Mark II. Oddly enough, you gain one light frame by shooting Raw + JPEG.

Apparently the way The EOS nD (single digit) cameras do this is by storing the frames in the buffer, then subtracting the dark from them in one batch and spitting them all out to the memory card. I can't understand how also shooting JPEGs in this process buys you one more light frame. (I would think it would be the opposite, that there'd be even less buffer memory available. But for some reason, if you shoot only JPEG, you get one fewer light frame. ) Nonetheless, I just verified this with my 6D.

Edited by mmalik, 21 December 2014 - 09:12 PM.