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DSLR - how many megapixels to use?


xanthic

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I've got a camera capable of capturing 18 MP. It is actually worth using them all or better to capture at a lower setting (processing time aside)?


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The more mega-pixels the bigger the file size, the longer to process! I use 7.5Mp although the camera does upto 12Mp. Just my 2 penneth!


 


Ron


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Guest peepshow

Just some meandering thoughts..............


 


If one has a 20 inch monitor, say, on which to view on, then that is approx. 200 sq inches in area.


 


At normal viewing distance one cannot resolve smaller that about .005 inches effective pixel and many not even that. 


 


(my meanderings are all  'approx' and 'about' :) )


 


.005 inches gives about 40,000  pixels per sq inch (200x200), which is 8 million pixels in total.


 


That seems more than enough for that particular monitor to show,


 


So the number of pixels one uses depends on the viewing medium methinks.


 


If you view results  on a mobile then about ( :) )  6 pixels will suffice ;)

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I know nothing about anything, but if the only draw back is an extra 2 minutes of stacking time, then I'd have thought the potential benefits of greater resolution would win. If the extra processing time is an hour, then again it depends whether you can just leave the computer processing and do something [less boring in stead] and come back to it later.


 


But if pro's like Ron are using less than the full capacity of the sensor, there must be value in doing so.


 


I'll be interested to follow this thread.


 


James

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For taking astro pictures you should be using your camera in RAW mode so it will always use all the pixels.


RAW is untouched by the camera, more or less.


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That may depend on your camera. My Canon 7D is able to take RAW frames at 4.5, 10 and 18M. The mighty Atik 11000 "only" produces 10M frames (and I realise it is a different class before the pendantry alarms go off ;) ). Just curious if the extra pixels make for a better quality image.

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That may depend on your camera. My Canon 7D is able to take RAW frames at 4.5, 10 and 18M. The mighty Atik 11000 "only" produces 10M frames (and I realise it is a different class before the pendantry alarms go off ;) ). Just curious if the extra pixels make for a better quality image.

Show off  :P

Interesting thread here - http://www.canonrumors.com/forum/index.php?topic=9173.0

I would stick to full RAW going on the info in that thread.

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Thanks Andy - One of the comments in that thread said "Why throw data away". Seems it really is just the balance between processing time and disk space over image quality. 


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Guest Kheldar

Depending on the focal length of your scopes there's a HUGE argument for binning the data ... more pixels do not always equal a better image :)


Edited by Kheldar
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Depending on the focal length of your scopes there's a HUGE argument for binning the data ... more pixels do not always equal a better image :)

True, but from what I read in the photography forum it does have an effect on the image with the DSLR.

I assume the 7D is a full frame sensor so it will crop well without loss of resolution in post processing.

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Guest Kheldar

True, but from what I read in the photography forum it does have an effect on the image with the DSLR.

I assume the 7D is a full frame sensor so it will crop well without loss of resolution in post processing.

 

I don't think you're looking at this from the same perspective that I am?

Nothing to do with cropping, it's binning - I'm coming at this from an arcseconds per pixel and under-sampling perspective here

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The 7D is a cropped sensor. So which way around does it work?, For my F5 scope, is it worth binning? I'm guessing the higher the ratio, the less need to bin?


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Guest Kheldar

For your 7D and 150P you're getting 1.1 arcsecond/pixel ... that in my book (and not that it prevents you imaging or produces bad results in the slightest) is undersampled for UK skies ...


 


I would bin 2x2, still keep a healthy resolution and get 2.2 arcseconds/pixel and get more data :) This I believe will result in even better images!


 


Just my 2p ...


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Guest Kheldar

Omg what is binning?!

 

Binning is combining pixels into MEGA-PIXELS!!! :D

 

It groups them in blocks (2x2, 3x3) and those pixels in the block are read as a single pixel.

 

Effectively makes the size of the pixels in the camera bigger, but reduces resolution, but increases sampling.

 

It's all trade offs :)

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For your 7D and 150P you're getting 1.1 arcsecond/pixel ... that in my book (and not that it prevents you imaging or produces bad results in the slightest) is undersampled for UK skies ...

 

I would bin 2x2, still keep a healthy resolution and get 2.2 arcseconds/pixel and get more data :) This I believe will result in even better images!

 

Just my 2p ...

I'm certainly going to give it a go. I realise I've not got the best setup but am keen to get the best I can until I'm able to upgrade.

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I don't think you're looking at this from the same perspective that I am?

Nothing to do with cropping, it's binning - I'm coming at this from an arcseconds per pixel and under-sampling perspective here

I understand Binning (I use it for framing only with my small CCD) I was just meaning that you can crop tighter in post processing and produce fine images.

From the photography forum it seems that the lower resolutions are from binning but they also say it affects the output image.

 

I would have a play on one target and see which one comes out best.

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Guest Kheldar

I understand Binning (I use it for framing only with my small CCD) I was just meaning that you can crop tighter in post processing and produce fine images.

From the photography forum it seems that the lower resolutions are from binning but they also say it affects the output image.

 

I would have a play on one target and see which one comes out best.

 

:thumbsup:

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So how does one bin data? Is this a setting in the camera or the stacking software, or something else? I've not tried this yet. A fools guide please, nothing too technical.


 


Edit: I think I have found the settings in DSS it says to combine to produce super pixels, is that the same thing yes?


Edited by Perkil8r
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Guest Kheldar

So how does one bin data? Is this a setting in the camera or the stacking software, or something else? I've not tried this yet. A fools guide please, nothing too technical.

 

Edit: I think I have found the settings in DSS it says to combine to produce super pixels, is that the same thing yes?

 

DSS may be able to do it retrospectively however I'd look for a setting on the camera itself of the capture software to do it

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Doesn't have it on less posh Canons only on the pro ones.


On the basic Canons RAW is full sensor output only.


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