![]() ![]() For comparison, still photos comprise only RAW (uncompressed) images, which have 12–14 bit image data, and are often lossless compressed (highest quality). This is mainly an issue if you later want to perform major color editing (e.g., significantly change the white balance).Ĭompression dramatically changes the video you are saving, and reduces the options for major editing at a later time using video editing software. Although this is a plus, it also means that at a given bit rate the JPEG compression is more lossy (resulting in a lower quality image).Īll these camera codecs use something called chroma sub sampling, whereby the compression process discards some of the color information. MJPEG, unlike the GOP codecs, compresses each image independently. That is why we transcode (convert from one codec to a different one) all our footage to a higher quality non-GOP codec (e.g., Apple ProRes LT) for further editing. There is a downside to GOP compression codecs: they do not perform well during video editing. DSLR cameras often have fast processors for performing this complex compression task. This means that the compression scheme is very efficient if nothing moves in the video, but it’s more challenging if things move fast. The subsequent frames of the group store only delta information to the first one. The first frame in the group, although still compressed, is stored in full. ![]() The GOP codecs compress a group of images as a whole. MPEG-4 GOP (Group of Pictures) codec, used by CanonĪVCHD (MTS video files) GOP codec, used by Panasonic GH1 and Sony NEX-5 MJPEG (Motion JPEG) codec, used by Nikon and Olympus Three main compression schemes are currently used in DSLRs: This is done through the compression process. Compression, therefore, is essential to a Video DSLR working properly for any length of time.Īll cameras need to limit the bit rate (maximum data per second created for the video stream) to ensure that the recording does not exceed the memory card’s maximum sustained write speed. Uncompressed video would also quickly exceed the maximum sustained write speed, meaning that it would be attempting to write to the memory card faster than the memory card could save (“write”) the images. Without compression, the camera memory card would be full in no time. It helps to understand the types of video compression performed by today’s Video DSLRs. We wrote an updated and more complete article for DPReview that can be found here. Review diary by Bettina + Uwe Steinmueller Please Visit the all new Digital Outback Photo ![]()
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