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Olympus OM-D E-M1 The first Micro Four Thirds camera that offers phase detect focusing so you can use Four Thirds DSLR lenses normally as well a Micro Four Thirds lenses.

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  #31  
Old 25th November 2014
birdboy birdboy is offline
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Re: Picture Mode and RAW

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Originally Posted by OM USer View Post
Some points we should bear in mind:

You can't apply your settings (highlight/shadow, contrast, vibrancy, mono, art filters etc) directly to a jpeg. You have to decompress the jpeg, apply the settings, and then save as a jpeg.
Of course you can apply highlight/shadow, contrast, vibrancy, mono, art filters etc to jpeg files directly, but I donít think thatís what you are trying to say. Jpegs still have pixel specific data which can be manipulated in software albeit not as effective as a raw file.

I have no detailed knowledge of how things are done in cameras but I do support the view that it matters what jpegs settings are set even if you shoot raw.

In your explanation you have explained that there are sensor and viewing devices. You have explained that jpegs are a lossy file which requires some processing. I think you are deducing that the camera software therefore uses some other CDAF algorithm based on the raw file.

The sensor (OMD-EM1) has in simple terms approx 16,280,000 effective pixels. The Viewfinder has 2,360,000 pixels () and the LCD has approx 1,040,000 dots. So there is clearly some loss reduction of image data going on in the camera in real time.

As the camera already has a jpeg algorithm built into its software it would make sense that it was used in transferring the sensor image information to the camera LCD or viewfinder rather than having another algorithm requiring even more processing.

It has been mentioned on here before that it is likely that the software inside the camera is of the same basic build as the Olympus Viewer software which gives you the jpeg view when you open a RAW file in it. Within that software you can change many things especially if you still have the raw data. Contrast is one of the things you can change. The camera then can make a contrast change for purposes of focusing using that same program. So why would the camera manufacturer use a different contrast algorithm based upon raw data and not the smaller faster jpeg file which it already has?

But how does a RAW file with 16,280,000 effective pixels (colour) become a B&W image 2,360,000 pixels without processing. My answer is that it is converted into a smaller file (i.e a jpeg) internally within the camera in real time.

A RAW file is just a file with exif data including a thumbnail jpeg (surely thatís a clue) with all the raw pixel data. Raw files require some form of camera specific processing so that we see them as an image.

My take on what is going on is that the camera first scans the sensor and stores that information as a basic RAW file it then reduces and coverts that data into a jpeg file based upon the jpeg settings in the camera adding a thumbnail jpeg to the RAW file. Next it looks at the pixels corresponding to the focus points (if in an AF mode) and does some contrast detection. If there are adjustments to focusing required (in AF modes) it makes that adjustment and as it is re-sampling all the time anyway carries that on until the shutter button is pressed at which point it then saves the files dependent on what you have selected in your camera discarding those temp files it used.

So my conclusion is that as this is a mirrorless camera what you see in your viewfinder and LCD are jpegs based images and it matters therefore what jpeg settings you have set.

Of course I could be wrong.
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  #32  
Old 25th November 2014
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Re: Picture Mode and RAW

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Originally Posted by birdboy View Post
So my conclusion is that as this is a mirrorless camera what you see in your viewfinder and LCD are jpegs based images and it matters therefore what jpeg settings you have set.
I am far from convinced by your argument. JPEG, as stated before in this thread, is a (lossy) compression algorithm as such it requires a substantial amount of processing. To display a sensor image in the viewfinder or on the screen does not demand compression but rather resizing. I would venture to suggest that executing a purpose built resizing algorithm would be significantly faster (given same processing engine) than performing a JPEG compression and what is more it does not have to conform to any international standards.

The JPEG files for storing on the card can be produced almost at leisure in the background and maybe even by using a different processor.
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  #33  
Old 25th November 2014
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Re: Picture Mode and RAW

You know, the more I read this thread the more I realize how little I actually know about this topic.
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  #34  
Old 25th November 2014
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Re: Picture Mode and RAW

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Originally Posted by Zuiko View Post
You know, the more I read this thread the more I realize how little I actually know about this topic.
I think all of us, especially myself, are only "supposing" and none of us actually know how the camera's firmware is configured. Unless of course one of us is an Olympus systems engineer in disguise?
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  #35  
Old 25th November 2014
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Re: Picture Mode and RAW

A bit more on JPEGS - but only a bit as I am no expert.

Jpegs do not have pixel specific data per se. Part of the compression algorithm throws away some data but allows a close approximation to the the missing data to be calculated based on a stored difference to preceeding data or by interpolation based on the values either side if it. Jpegs do however have a stored image size and of course a physical size (in bytes) when stored on disk, the latter dependent on the compression factor (the amount of loss) applied. I really was saying that you can not apply image processing directly to a jpeg... and that includes viewing it.

The thumbnail jpeg stored in the RAW file is heavily compressed with a lot of data thrown away. It occupies much less disk space than the jpeg file stored by the camera on disk (if so chosen). I do not know if this thumbnail is actually a reduced size image and so what we would conventionally refer to as a thumbnail (compressed of course via the jpeg algorithm for storage) or just very heavily compressed full size image that on decompressing creates a full size image with most of the pixels interpolated (one perhaps for those who like RawDigger). This is why when opening a RAW file in an image viewer you first see a rough approximation of the image (a de-jpegged thumbnail) that then sharpens up as the RAW image data is processed into a bitmap for viewing - note that to view the RAW data it is converted into a bitmap and not a jpeg (just as a jpeg needs to be converted into a bitmap to view).

I too admit, as others do in this discussion, that I could be wrong.
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  #36  
Old 25th November 2014
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Re: Picture Mode and RAW

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Originally Posted by Adagio View Post
I am far from convinced by your argument. JPEG, as stated before in this thread, is a (lossy) compression algorithm as such it requires a substantial amount of processing. To display a sensor image in the viewfinder or on the screen does not demand compression but rather resizing. I would venture to suggest that executing a purpose built resizing algorithm would be significantly faster (given same processing engine) than performing a JPEG compression and what is more it does not have to conform to any international standards.

The JPEG files for storing on the card can be produced almost at leisure in the background and maybe even by using a different processor.
I do not know if jpeg compression needs a substantial amount of processing (whatever that may equate to) but I do know that working with jpegs files is much much faster than working with raw files Your last sentence would not make sense if the processing to jpegs is substantial as the camera is capable of 10fps.

What does require a substantial amount of processing is working with raw files that are 13MB in size compared to a 2Mpixels jpeg of 208KB.

My point is that the jpeg software is already in the camera's firmware so has to conform to the jpeg standard. My simple test of using B&W filter jpeg setting shows that it must be doing some jpeg conversion in real time. I have tried it with other jpeg settings and noticed a change in the histogram so I feel that it confirms my thinking.

But I respect others thought process as stimulating which is why I like this forum.
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  #37  
Old 26th November 2014
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Re: Picture Mode and RAW

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Originally Posted by Phill D View Post
Why doesn't someone ask Olympus to comment on this? Ian/Mark can you follow this up?
Chevvy explained it to me at the Giffords Circus event and I tried it for a while. Not sure I could tell any difference though except it messed up my jpgs as expected so I reverted back to my normal settings.

To Olympus, my question:

My question is does contrast, RGB, sharpness and even Vivid picture mode directly adjust the sensor sensitivity or are they applied after by the True Pic engine? There is the theory by adjusting these settings in the SCP makes the AF more sensitive.

From Olympus Tech Support:

Dear Val,

Thank you for your email regarding your OM-D camera.

Please be advised that contrast, RGB, sharpness and Vivid picture mode do not adjust the sensor sensitivity. These settings are indeed applied afterwards by the True Pic engine.

Should you require any further assistance, please do not hesitate to contact me.

Kind regards,
Jaroslav Zika

Technical Support Specialist

So a placebo of sorts thinking adjusting those settings made a difference. BUT there have been one or two times I have had focus issues and turned up contrast and the problem resolved.
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  #38  
Old 26th November 2014
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Re: Picture Mode and RAW

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Originally Posted by pvasc View Post
To Olympus, my question:

My question is does contrast, RGB, sharpness and even Vivid picture mode directly adjust the sensor sensitivity or are they applied after by the True Pic engine? There is the theory by adjusting these settings in the SCP makes the AF more sensitive.

From Olympus Tech Support:

Dear Val,

Thank you for your email regarding your OM-D camera.

Please be advised that contrast, RGB, sharpness and Vivid picture mode do not adjust the sensor sensitivity. These settings are indeed applied afterwards by the True Pic engine.

Should you require any further assistance, please do not hesitate to contact me.

Kind regards,
Jaroslav Zika

Technical Support Specialist

So a placebo of sorts thinking adjusting those settings made a difference. BUT there have been one or two times I have had focus issues and turned up contrast and the problem resolved.
Does this really answer the question regarding focus. What is sensor sensitivity?

I would not thought the sensitivity of the sensor to play a part. I thought we were talking about what the camera does with the raw data once it has collected it and does the True Pic Engine use it for CDAF.
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  #39  
Old 26th November 2014
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Re: Picture Mode and RAW

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Originally Posted by birdboy View Post
Does this really answer the question regarding focus. What is sensor sensitivity?

I would not thought the sensitivity of the sensor to play a part. I thought we were talking about what the camera does with the raw data once it has collected it and does the True Pic Engine use it for CDAF.
Poor wording on my part. By sensitivity I meant does turning up contrast make the sensor focus better. I think he knew what I meant.

We were talking about what the camera did with the Raw data, I kinda highjacked the thread a bit, sorry.
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