Since then I have seen this effect in many images (in localized areas), and as I stated way back in my first reaction, it is an image quality defect that I have not seen over the years of shooting my Nikon D800/D800E. But as Alex points out, probabilities tend to result in clumping (non randomness) in visible effects, an idea I fully support in seeing some coarseness in tonal transitions, an effect I immediately detected (by eye), and immediately commented up on in my review when first shooting the A7R. The general “internet rejection” of this stepping delta idea relies on the premise that photon noise exceeds the stepping.The effective stepping can be around 3.4% which is very much discernible by the eye., the figure of around 1% can be considered just discernible. ![]() So, if data range within 16 pixels is too wide, then “step size” of each transition increases, so posterization occurs. Pixel value = minimum + delta_recorded_for_this_pixel * step. This 'step' is the same for all 'delta' pixels in block (smallest integer power of two (1,2,4.) such that step*128 > max-min) Step = (maximum - minimum)_rounded_to_the_nearest_largest_power_of_two / 128. = 11 + 4 + 11 + 4 + 14 * 7 = 128 bits for 16 pixels = 8 bits per byteģ) 'delta' pixel value is calculated from delta, minimum and maximum: and 14 7-bit deltas for remaining 14 pixels. The minimum and maximum values in block - two 4-bit coordinates of min/max pixels in block are stored too. According to Alex:ġ) In each 32 pixel block we have 16 pixels of single color.Ģ) For the 16 pixels of each color: - two 11-bit values ('base pixels') are stored exactly. On my to do list is exploring these new Sony-specific features, which appeared just recently. RawDigger is the only tool to display areas that might be subject to posterization due to Sony lossy compression. You can read it in Russian or in the Google translation. There is a difference, and I am certain it explains some of the not-so-great pixel quality I’ve seen in field images (in localized areas, not in totality), but it has been hard to pin down.Īlex Tutabalin of RawDigger has posted an essay on the posterization effects that can be observed with Sony ARW raw files due to the 7-bit delta compression. Compare that to a Nikon 14-bit lossless image file. Order the Sony Vario-Tessar T* FE 24-70mm f/4 ZA OSS Lens at B&H Photo.Īs discussed in some detail in the review of the Sony A7R, the Sony A7 and A7R and other Sony cameras all use an 11 + 7-bit lossy compression scheme: 11-bit range with 7-bit delta values from 14-bit pipeline (8 bits per pixel in effect). Update: Sony A7R II offers lossless compression option. SEND FEEDBACK Related: exposure, histogram, LibRaw, noise, RawDigger, Sony, Sony A7, Sony A7 II, Sony mirrorless
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