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Thread: Some questions about the P25 back...anyone?

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    Senior Member Chris Giles's Avatar
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    Some questions about the P25 back...anyone?

    Ok, on my trip down the rabbit hole my Leaf Aptus 22 has gone back to Leaf for calibration.
    It appears the focus issue I was having is down to the back, not the bodies much to Pear tree's surprise.

    In the meantime though, I picked up a P25 back for Hasselblad (H101) and I've a few questions about it if anyone can help.

    Firstly, I was surprised that the Raw files were tiffs. My experience of Tiffs is that you can't white balance correct them like Raw files...but I can with these?

    Also, file sizes are half the Raw size of the leaf 22's...anything to note here?

    I thought the non + backs that went to ISO800 had half file size to obtain the high ISO. But on this back the dimensions remain the same.

    Also, for a 22mp back, the file dimensions are 2581 x 1937 for IIQ Raw L and IIQ Raw S - Which seems odd and doesn't ring true for 22mp...and no 'uncompressed' option?

    If anyone can advise, particularly in the regard to file sizes. Camera is a H1 Hasselblad. Thanks!
    Last edited by Chris Giles; 26th March 2012 at 11:15.

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    Senior Member Chris Giles's Avatar
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    Re: Some questions about the P25 back...anyone?

    Wow, major head screw here, windows reports the file dimensions as 2581 x 1937 but open them in photoshop or export them as JPEGs and they become 5450 x 4090??!?

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    Re: Some questions about the P25 back...anyone?

    Phase One's original RAW files (prior to a RAW being an industry recognised format) had a .tif extension even though they were RAW files. I think it was changed in the plus backs as digital capture was more widely adopted.

    The way to tell if its a regular photoshop .tif or Phase RAW .tif is to open in C1 and in the metadata/info tab look under basic and at the format. If its a RAW file it will tell you the extension (IIQ L or IIQ S).

    As far as I remember ISO800 on a non Plus back should be at full resolution. Pixel binning (sensor+) came much later on.

    What does C1 report as to the pixel dimensions?

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    Senior Member Chris Giles's Avatar
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    Re: Some questions about the P25 back...anyone?

    Hi Gareth,
    In Capture 1, a 22mp tiff/raw file shows as a 108mb Tiff.
    Image dimensions are as they should be. There is a huge difference in the way the images look in Capture 1 versus Lightroom 4.
    (Straight forward open, export to Jpeg)


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    Re: Some questions about the P25 back...anyone?

    The default setting in C1 is to apply a response curve as standard.

    My guess is LR4 does nothing to the RAW file and you would get pretty similar result if you choose "Linear Response" in the Base Characteristics tab of C1. However saying that, I've never liked using LR and always been a C1 users for both my Canon and Phase files as I always felt the conversion was much better. I don't have any experience with LR4 though.

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    Subscriber & Workshop Member GrahamWelland's Avatar
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    Re: Some questions about the P25 back...anyone?

    Btw, in general you will find that most raw files are actually some derivative of a TIFF file even if they have a different naming convention. Tagged Image File Format is a very flexible file encoding scheme that can basically hold any combination of byte sets such as image data as well as meta data about the image (I.e. data about how to process it for example such as white balance, orientation, multiple renditions etc etc). Basically you have multiple sets of data with a unique tag and then the data stream that goes with it. (there's a lot more to it but you get the idea - in a previous life I developed a complete TIFF library so I bear the scars ...)

    Regarding the strange image size issue, I suspect that Windows is misinterpreting the dimension data or perhaps referencing an embedded preview jpg rather than the raw data itself.

    As regards the ISO 800 file, my understanding is that it is supposed to be half dimension at that resolution with the P25 as compared to full resolution with the P25+. On that original back they did pixel bin for ISO 800 only.
    Remember: adventure before dementia!

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    Re: Some questions about the P25 back...anyone?

    Phase One camera profiles in ACR are not good at all. You should see the one for the P25+
    EVERYTHING IS WAY THE HELL OFF.

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    Senior Member Chris Giles's Avatar
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    Re: Some questions about the P25 back...anyone?

    Quote Originally Posted by FredBGG View Post
    Phase One camera profiles in ACR are not good at all. You should see the one for the P25+
    EVERYTHING IS WAY THE HELL OFF.
    I wonder why that is?

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