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Olympus OM-D E-M5 The first Micro Four Thirds camera from Olympus with an integrated Electronic Viewfinder

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  #16  
Old 31st January 2016
Ricoh Ricoh is offline
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Re: Max pixels?

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Originally Posted by pdk42 View Post
The size of the file is not constant. It will vary with ISO and the amount of detail in the shot. All that matters for Mp is the dimensions of the image in pixels.

Raw file size varies because the data undergoes lossless compression. In crude terms, if there is lots of repeating data then the data can be compressed to omit the repetition. As ISO goes up so does noise and this reduces the scope for repeating data so you'll see larger files at high ISO. Since noise increases in shadows you'll also see an inflation in darker images, all other things being equal. The same is true for shots at low ISO with lots of fine detail.
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  #17  
Old 31st January 2016
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Re: Max pixels?

Amplifying Steambuff's comment, can we go back to square 1? When you say you are only getting 14.3M, what exactly are you referring to? Size of raw file on disk in bytes? Size of JPEG, TIFF or some other format file? What a program like Photoshop tells you is the image size once you have opened it?

All these things can vary for all sorts of reasons. JPEGs can vary dramatically depending on how much compression it can do, I think TIFFs can also vary as they can have some lossless compression which will vary by subject. With some cameras the size of the raw file is always the same, but for some reason looking back at some old E-M5 files it appears to vary quite a bit between about 13 and 15 Mb. I'm not sure why this is, it does rather suggest that the raw files are not quite as raw as we might think!

The only true measure of resolution is the pixel count so if you are seeing 4608 x 3456 it is not short-changing you.

John
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Old 31st January 2016
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Re: Max pixels?

Sorry, John, should have said RAW files, blame old age . You are the second person to mention that file size varies on the EM-5, so, perhaps it is more to do with available light or similar or internal camera workings.

I will persevere and keep note on what transpires, thanks to all for your input, much appreciated.
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Old 31st January 2016
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Re: Max pixels?

I just had a little trawl through lots of folders of old photos from different cameras. With most of them, including all the Olys back to the E-1, they vary a bit from shot to shot. At a guess I'd say there can be about +/- 10% variation. Some cameras use DNG format, those files seem to show very small variation, I think because any edits applied are stored within the DNG file itself rather than in a separate file.

It sounds as though you don't have anything to worry about and the camera is working normally.

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Old 31st January 2016
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Re: Max pixels?

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Originally Posted by Imageryone View Post
Thanks for this , Paul, but I only use ISO 100 on all cameras except in very, exceptional circumstances, but I do use Exposure comp all the time, usually set at -0.7, which, as you explain, would effect the size of the file. I will turn it off and try again
Are you confusing pixels and megabytes ?

As others have said in earlier posts the files size in megabytes depends on how much detail is in the picture regardless of what ISO, exposure comp, or whether RAW or JPG is set.

eg. a picture that takes up the whole image of say just blue sky with no clouds will be a lot smaller in terms of Megabytes file size than a picture of say a lot of trees.

The image size in pixel terms is fixed by the cameras settings, e.g.. 16 x 9 or 4x3 etc.

Could you provide a link to an example where the size is wrong. Cant do it on here because of the restrictions on file size.
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Old 31st January 2016
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Re: Max pixels?

Hi Dave,
think I expecting a lot from what, to me , is a new type of camera. Taking into consideration points already mentioned by forum members, I need to use the camera in more varied conditions and subjects before any worry.
It seems that the file size on the EM-5 does vary quite a bit from image to image, just need to keep a weather eye on it, Thanks for your input,

David
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Old 31st January 2016
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Re: Max pixels?

David.
I have done an investigation and concluded that your problem may be nothing to do with the camera but due to the settings in FastStone.

I use F.S but only these days for a few tweaks on JPEGs. I checked some files from yesterday's outing which I had previously processed from raw in Dxo Optics Pro where of course they showed as 4608 x 3456 pixels. In FS they show in the Preview window (bottom LHS) as 3200 x 2400 ie. half size but if you "hover" the mouse cursor over the thumbnail in the gallery they show as 4640 x 3472 (more about this discrepancy later). More disturbingly when I did the raw conversion in FS it produced a half size JPEG.

If you go to the FS "Settings" panel and look at the "raw" section the first line is a "View RAW Files in: " box. Change this to "Actual Size (Slow)" and tick the box. This will now show the correct size data in the Preview window and, perhaps more importantly will produce the full size JPEG on conversion.

Now the discrepancy between 4608 x 3456 and 4640 x 3472 pixels. I remember from the days when I did use FS for raw conversion that it always did this. Olympus have decided for whatever reason that 4608 x 3456 is the size that they want and the camera processing engine produces this size JPEGs but the sensor is actually slightly larger. Commercial raw processing products (Adobe/DxO etc) follow this convention but FS being a "universal" converter does not. Bonus pixels.

In post #15 you say you always use "ISO 100". This is not necessarily a good idea. Olympus deliberately call it "ISO LOW". The "native" ie. inherent sensitivity of the sensor is ISO 200 and "ISO LOW" is a fudge to degrade this and causes a reduction in dynamic range.

Hope this helps.
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  #23  
Old 31st January 2016
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Re: Max pixels?

Thanks Peter,
more avenues to explore, always good to have a learning curve and good people to point the right direction.
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Old 8th February 2016
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Re: Max pixels?

Found the missing Pixels..

Went through menus and sub menus with no luck, then went through shooting prefs on the top dial and found auto adjustments turned on in SCN mode.
Switched them all off and now get a constant 15.3 - 16,3m resolution between shots.

Problem solved. Thanks to all for your input.
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  #25  
Old 9th February 2016
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Re: Max pixels?

Glad you've cracked it.

You have inadvertantly found one of those instances where the camera thinks it knows best.

Regards.
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Old 10th February 2016
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Re: Max pixels?

I've just looked at some photos I took the other day with an EM1 and the 12-40. All are of monochrome magazine pages so the subjects are quite similar. I used LN compression to keep the file size down so they're well below maximum size. What is interesting is that of a set of six the largest was 3.516Mb and the smallest 2.750Mb. In other words a variation in file size is to be expected even if subjects are broadly similar.
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