RAW and sensor?

Discussion in 'Photography Beginners' Forum' started by Leilameat, Aug 10, 2010.

  1. Leilameat

    Leilameat TPF Noob!

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    What exactly is a RAW file, and why does a camera only shoot a few of them? Is it better than JPEG? If so, why?

    And also, what's the difference between a full frame sensor, and a crop sensor?
    Why is full frame better for wildlife, and why is a crop worse?
    Is it very bad the Canon 7d has a crop sensor?

    Thank you, guys! :D
     
  2. NiceShot

    NiceShot TPF Noob!

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  3. KmH

    KmH Helping photographers learn to fish Supporting Member

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    All digital cameras record RAW image data every time the shutter is released.

    A RAW file has had little editing done to it in the camera and has either a 12-bit (4096 levels) or 14-bit (16,384 levels) tone depth per channel, depending on the camera.

    A JPEG is made from that RAW file, but JPEG is a lossy compressed image format that only has an 8-bit depth (255 levels of tone). JPEG reduces the size of the image file by discarding image information, mostly color info. A RAW file made by a 10 MP camera will result in a file that is approximately 30 MB in size. When that file is converted to a JPEG it is usually reduced in size by a 4:1 ratio (to about 7 MB)

    The loss of all that data seriously decreases the amount of editing headrooom any JPEG will have. Which is understandable since JPEG was designed to be a print image file that receivers no additional editing.

    When a camera is set to JPEG the RAW file is not only compressed, it is also edited is so far as the contrast, saturation, and sharpening are altered based on the image processor editing and any user, menu selected settings in the camera. That editing is also done to the image globally, or the whole image. Editing of RAW images editing is often done locally, or on only part(s) of an image. It makes little sense to use shallow depth of field to throw a background out of focus, and then apply sharpening to it in post processing, as just one example.

    So, RAW is used when the photographer wants to personally make adjustments to their images, and JPEG is used when the photographer wants the camera to write ready-to-print image files to the memory card.
     
    Last edited: Aug 10, 2010
  4. clanthar

    clanthar TPF Noob!

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    Hi,

    As for your concern about the 7d: It's bad that the sensor on the 7d isn't full frame, but then, if it was, it would be bad that it wasn't as big as the sensor on the H4d-50 which is twice as big as full frame. However it's also bad that the H4d-50 costs around $25,000.00 (at least from my perspective).

    So, the 7d is a very capable camera at a reasonable price. You can't get a full frame sensor camera for the same price. I have a couple friends who have the 7d and I've seen some excellent photos come out it. It's not the best money can buy, but how much money you got?

    Joe
     
  5. Leilameat

    Leilameat TPF Noob!

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    Thanks for the info.
    But still, I don't quite get what makes the crop versus full frame inferior.
    How is it worse?
     
  6. Robin Usagani

    Robin Usagani Been spending a lot of time on here!

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    Actually a lot of wildlife photog prefer cropped sensor because you automatically get 1.5 or 1.6X magnification with the sensor.

    The RAW stores a lot more information and a lot larger. Thats why your card can only take so many RAWs. Also, if you shoot in a burst mode, sometime your camera isnt fast enough to write big files like RAW or RAW+JPG so you can only take 4-5 shots in a row burst mode. But if you do only JPEG you can take a lot in a row depending on the quality of the jpeg, your camera, and your card writing speed.
     
  7. Gaerek

    Gaerek TPF Noob!

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    The short answer is, a full frame sensor will typically have less noise at higher ISOs. There's some other advantages, but that's them most commonly cited one at the moment.

    In reality, if you're asking this question, it's very likely you won't notice, or care about this difference. The 7d is a very good camera that probably has the best high ISO to noise ratio of any cropped frame sensor out there today.
     
  8. sovietdoc

    sovietdoc TPF Noob!

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    FF cams are better than crop because they provide a lot more FoV in your pics, while at the same time being able to flip the switch and let their sensor run at 1.6 crop.

    FF can do crop, crop can't do FF.

    I am sure once all cams will move to usb 3 with next gen flash crads, there will be no problem in writing raw's while bust shooting.
     
  9. clanthar

    clanthar TPF Noob!

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    Hi,

    This difference isn't huge, but, DOF will be different between the two cameras. DOF is a function of f/stop and magnification. The smaller sensor reduces magnification and so increases DOF.

    For good control of DOF (especially the ability to produce selective focus in portraits) an ideal sensor size would be about 2 to 3 times larger than full frame. Full frame is short for 35mm which back in the days of film was considered small format. Medium format film cameras used film that was roughly between 1.5x2 to 2x3 inches. This size film produced the ideal magnification/DOF relationship for portraiture.

    So, as the sensor size in digital cameras shrunk DOF in general increased -- to the point where you can't get rid of too much DOF if you don't want it.

    Compared with a full frame sensor camera, the 7d will produce photos with more DOF all else being equal.

    Joe
     
  10. benlonghair

    benlonghair TPF Noob!

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    Is this true? My D60 produces RAWs that are about 8-10mb. How does this work?
     
  11. o hey tyler

    o hey tyler Been spending a lot of time on here!

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    I don't think you can "switch" a camera from FX to DX. The sensor size is still the same. Are you sure you know what you're talking about?
     
  12. ann

    ann No longer a newbie, moving up!

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    if you use a dx lens on a ff sensor, the camera will automaticaly crop out some information and so one ends up with using less sensor area
     

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