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Equipment Discussions >> Electronically Assisted Astronomy

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mpgxsvcd
Carpal Tunnel


Reged: 12/21/11

Loc: Raleigh, North Carolina
An Experiment in Dynamic Range new
      #5611235 - 01/08/13 12:19 AM Attachment (41 downloads)

I wanted to push the Panasonic GH3 to its limits of Dynamic Range.

Here are three images. The first is an in camera HDR image. This is the out of camera jpg image and is representative of what it looks like on the LCD screen or when output over HDMI to a monitor. It is comprised of 3 images. An 8 second, a 1 second, and a 1 minute exposure.

All of these three images were shot at ISO 12,800. You can see how the HDR image not only increases the perceived dynamic range but it also drastically reduces noise through the in camera stacking process.

The final image is a stack of Ten 1 minute and 9 second jpg exposures.

Please note that this camera still has the stock filter in place so all UV, Ha, and IR light is removed.

A single in camera HDR image. Total of 3 images(8 seconds, 1 second, and 60 Seconds) @ ISO 12,800.

Edited by mpgxsvcd (01/08/13 10:09 AM)


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mpgxsvcd
Carpal Tunnel


Reged: 12/21/11

Loc: Raleigh, North Carolina
Re: An Experiment in Dynamic Range new [Re: mpgxsvcd]
      #5611237 - 01/08/13 12:21 AM Attachment (33 downloads)

A single 8 second exposure at ISO 12,800. This is what most people think of when they say Interchangeable lens cameras have too much noise.

The camera also has a mode where it could stack 4 8 second images and reduce the noise like the HDR image. It won't auto align in that mode though. However, in 32 seconds total even my CG-5 could track very well. I didn't get to try that mode last night because the clouds rolled in right as I was taking these images.

Edited by mpgxsvcd (01/08/13 09:20 AM)


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mpgxsvcd
Carpal Tunnel


Reged: 12/21/11

Loc: Raleigh, North Carolina
Re: An Experiment in Dynamic Range new [Re: mpgxsvcd]
      #5611242 - 01/08/13 12:21 AM Attachment (30 downloads)

This is the result of stacking 10 of the 1 minute and 9 second HDR jpg images in deep sky stacker. It is just for comparison purposes only. This is not a near real time image. No Darks, Flats, or Bias images.

Edited by mpgxsvcd (01/08/13 10:11 AM)


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mattflastro
Vendor - Astrovideo Systems


Reged: 07/31/09

Loc: Brevard County , FL
Re: An Experiment in Dynamic Range new [Re: mpgxsvcd]
      #5611578 - 01/08/13 09:27 AM

Travis, nice images. Impressve that they come straight from a camera with no computer processing (or should I say no EXTERNAL pc or computer) .
However, it is not clear for me what dynamic range are you testing here. Are we speaking camera dynamic range as defined by the maximum signal to noise+all other errors within a single capture? Are we speaking here stacked images dynamic range? For stacked images, the sky's the limit. Tell me your dynamic range target and I'll tell you for ANY given camera, even *BLEEP* 8 bit signal path ones, how many frames need to be stacked and what exposure times they need to have in order to reach your set dynamic range.
Obviously your test shows nothing regarding the camera electronics dynamic range , since all your posted images are stacked . The test shows also nothing of the dynamic range increase using stacking images taken with different exposure times, because the method is much more powerful and can be pushed really much more . You haven't even started to scratch the surface. Is it a test of in-camera on-the-fly stacking software? It seems to be, but this is NOT camera dynamic range . The camera hardware still has less than 14 bits dynamic range , the longest exposure of the 3 that are stacked still blows all the highlights , the shortest of them still has no details only noise in the dark areas, it's not a test of dynamic range, it's a show off of this camera's great processing convenience and capabilities .
If you want to test real hardware dynamic range, take a single shot of the same subject with varying exposure times until you get to not overexpose the core . Keep that single image. Do not manipulate the histogram , gamma , or curves in any way , and then measure the dynamic range on that image. That is what the camera dynamic range is .


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mpgxsvcd
Carpal Tunnel


Reged: 12/21/11

Loc: Raleigh, North Carolina
Re: An Experiment in Dynamic Range new [Re: mattflastro]
      #5611628 - 01/08/13 10:08 AM

@mattflastro

We are talking about the number of stops from clipped white to clipped black. Typically that is in the neighborhood of 10-14 stops for RAW images and less than 8 stops for jpg images.

I obviously didn't make myself clear in the first post. The first image is a stacked HDR image. However, it is all done in camera. The new Panasonic GH3 will take 3 consecutive images, align them, and then stack them to not only increase the perceived dynamic range but also decrease the noise.

The second image is a single exposure image. It was not stacked at all. It was ISO 12,800 so the noise is obvious. In addition you can see that this image blows out the core. Just compare it to the first image.

Now it is entirely true that the HDR images do not actually increase the dynamic range of the image. That would be impossible with an 8 bit jpg. However, what it does is compress the dynamic range of the scene. Thereby giving you the impression that it has more dynamic range than it really does.

If you can reproduce the first image in camera then I would love to see it and see how you did it. The HDR mode reduces the scenes dynamic range by up to 6 stops(+3 and -3 stops) there. That is a lot of dynamic range considering the GH3 does pretty well in that respect even with single exposure images.

The whole point of wanting extra dynamic range is so that you don’t blow out the core. That is what the HDR mode achieves without actually increasing the sensor’s or stored images dynamic range capabilities.

There are two ways to achieve the goal of not blowing out the core. You can increase the dynamic range of the sensor and the final output image or you can reduce the dynamic range of the scene itself. Increasing the dynamic range of the sensor would be very hard and costly to do. Therefore, decreasing the dynamic range of the scene is the next best thing. I think it is quite affective in doing that.


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mattflastro
Vendor - Astrovideo Systems


Reged: 07/31/09

Loc: Brevard County , FL
Re: An Experiment in Dynamic Range new [Re: mpgxsvcd]
      #5611703 - 01/08/13 10:46 AM

First, there's a huge difference between 10 and 14 stops . There's a one to one equivalence between stops and bits , so 10-14 stops is exactly the same as saying 10-14 bits A/D .
Big difference .10 bit is a very poor cam, 14 bit is the best . You need cooled sensors with large pixels and very low readout noise to achieve 14 bits or more.
Tiny APS-C cmos sensors and gazzillions of megapixels ain't it.
Second, your title was "dynamic range experiment" , which is not the same as "processing images for not blowing highlights" .
Third, stacking images with different exposure times and manipulating curves and histogram is called processing .
It has the capacity to improve the original image but it is not a measure of the CAMERA dynamic range.
I don't care whether you do the processing in the camera, in a computer, or whatever other means .
It's still processing and still has nothing to do with the hardware dynamic range .
I wouldn't argue with you if you titled your images "how panasonic gh3 doesn't blow hightlights by using in camera processing", because the truth is the results are great looking images considering the short exposures and the lack of out of camera computer processing .
But please don't make it sound as if by manipulating several images somehow the gh3 has really more dynamic range . It just has more processing built into the camera. You have a canned/pre-packaged stacking software in your camera and are trying to call it "high dynamc range camera" .
So to keep things in perspective, this is about how great the GH3 processes and stacks images with the in-camera software . Not to be confused with actual high dynamic range hardware , cooled ccd's, large pixels, low readout noise, e2ccd etc.


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mpgxsvcd
Carpal Tunnel


Reged: 12/21/11

Loc: Raleigh, North Carolina
Re: An Experiment in Dynamic Range new [Re: mattflastro]
      #5611734 - 01/08/13 10:59 AM

I never stated that the camera had more dynamic range because of this process. You inferred that.

This is most definitely an experiment in dynamic range.

What you are overlooking is that the camera has a dynamic range capacity AND the scene itself has a dynamic range. What I am doing is compressing the scene’s dynamic range to meet the camera’s dynamic range limitations. That was the experiment and it worked.

I never said I was doing anything different than that. You just thought that the term dynamic range only applies to the camera.


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mclewis1
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Reged: 02/25/06

Loc: New Brunswick, Canada
Re: An Experiment in Dynamic Range new [Re: mpgxsvcd]
      #5612073 - 01/08/13 02:31 PM

Travis,

Very intriguing thread.

Your first image in particular is very very interesting. In camera HDR is starting to show some neat benefits.

Folks should pay close attention to the stars of the Trapezium and surrounding nebula and the faint outer nebulousity. This first image really does represent a very impressive dynamic range. The second image is a much more traditional representation.

Historically to be able to represent the Orion nebula in this fashion you needed to a) with film do a lot of dodging in the darkroom or b) with digital take multiple short and longer exposure images and stack them on a PC.

Can you take us through how the camera is setup to take the combined 1, 8, and 60s exposures and how long it takes to present the final image?


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mpgxsvcd
Carpal Tunnel


Reged: 12/21/11

Loc: Raleigh, North Carolina
Re: An Experiment in Dynamic Range new [Re: mclewis1]
      #5612095 - 01/08/13 02:42 PM

Quote:

Travis,

Very intriguing thread.

Your first image in particular is very very interesting. In camera HDR is starting to show some neat benefits.

Folks should pay close attention to the stars of the Trapezium and surrounding nebula and the faint outer nebulousity. This first image really does represent a very impressive dynamic range. The second image is a much more traditional representation.

Historically to be able to represent the Orion nebula in this fashion you needed to a) with film do a lot of dodging in the darkroom or b) with digital take multiple short and longer exposure images and stack them on a PC.

Can you take us through how the camera is setup to take the combined 1, 8, and 60s exposures and how long it takes to present the final image?




Thanks Mark. Your synopsis is dead on.

The HDR process takes exactly 1 minute and 30 seconds from the time when I click the button until I see the full HDR image on the screen. That includes 10 seconds of shutter delay to let all vibrations subside. 1 minute and 9 seconds for the three images. And then 11 seconds for the camera to complete the HDR process and display the image. The camera is set to automatically display the image after it takes it and continue to display the image until I press the shutter button again.

In order to take an HDR image I simply click a quick button on the camera that toggles the HDR mode on and off. If I want to alter how the HDR is done I can dig into the menu structure and change that setting to Auto(The camera decides if it uses +-1, +-2, or +-3 stops of exposure) or I can manually chose one of those options.

For day time images I find Auto works well. For AP I have to manually set it. I tried all of them and +-3 worked best at 8 seconds for M42. It was noticeably worse at both 6 seconds and 10 seconds.

Once I figured out that +-3 worked best I simply stored that setting under a custom mode and now anytime I switch to the C2-3 custom mode it is setup to take the HDR image if I turn that option on with the quick button.

Please note that I cannot enable the HDR mode when viewing the camera remotely through my phone. However, I can enable that mode on the camera first and then start using the phone to control the camera. That means that I have to go back to the camera to disable that mode though.

Also the HDR mode can be setup to align or not align the images. If you use the aligning method then it reduces the field of view by a few percent and distortions can happen if the scope moves during different phases of the HDR process.

Edited by mpgxsvcd (01/08/13 02:49 PM)


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ccs_hello
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Reged: 07/03/04

Re: An Experiment in Dynamic Range [Re: mpgxsvcd]
      #5612547 - 01/08/13 07:11 PM

IMHO, life is too short to worry about the proper definitions of terminologies. To balance that point, "an educated consumer will always win the upper hand".
- HDR (in post-proc) is not sensor native D.R.
- Non in-sensor binning is not binning but summing in post
- A well known cult P&S with high ISO "rating" is really doing a great picture-level post
- A camera firm is remarketing higher-ISO speed but shorter exposure time as Image Stabilization
- Most of camera vendors are in mega-pixel race
- the list goes on and on

My 2 cents

Clear Skies!

ccs_hello


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