Intuition

During a recent trip to Sydney, I found myself in a condition where there’s only a single SD card with me, and I’ve forgotten my laptop at home for data export. So… I had to make sure I take every single shot carefully and not to use burst short to bloat up the memory, but this seems challenging since I am mostly walking down the CBD avenue and doing stree photography, not to mention I was constantly worried about running out of memory, although I managed to capture all my photos without any issues. As a result, once I returned home, I immediately began searching online for the largest SD card available, so I won’t have to be in the same dilemma agin. However, I was surprised to discover a dramatic difference in prices between V30 to V90 SD cards.

Storage SizeV30V60V90
128GB$49$109$269
256GB$89$209$519
512GB$269$399$949

While it’s clear that a high-tier SD card with superior writing and reading speeds will allow the camera’s cache to dump faster, as a photographer, I don’t mind waiting a bit longer beside my camera. After all, I’m not shooting anything in 4K at 120fps with 10-bit depth, which would require continuous data writing.

At least that’s how I thought …. it turns out my A7M4 only allows different image format for different SD card you have inserted, when you have “sort/simultaneous recording” option turned on:

StorageV30V60V90
JPEG
Lossless Compressed (S)
Lossless Compressed (M)
Lossless Compressed (L)
Compressed Raw
Uncompressed Raw

As a result I figure I will need to understand what format I need before burning all my money into buying the fourfold expensive V90 card, hence this post differentiating the image format.

Image Format Comparison

Color Bits

Most image formats use a color depth of 14 bits per color, which provides 16,384 different values. However, the “Compressed Raw” format reduces the color depth to 12 bits during continuous shooting mode.

8, 12, 14 vs 16-Bit Depth: What Do You Really Need?! | PetaPixel

Ouput Resolution

The “Uncompressed Raw”, “Lossless Raw (L)”, and “Compressed Raw” formats do not alter the resolution of the image; they output the same number of megapixels that the camera physically captures. In contrast, the “Lossless Raw (M)” and “Lossless Raw (S)” formats compress the image resolution by factors of 2x and 4x, respectively.

2025-01-16T193420

2025-01-16T190911

Frame Shot Per Second

The image format “Compressed Raw” format provides higher frame per shot second (≈ 10 fps) than the other formats which is sometimes worth it while shooting fast moving object in continuous shooting or burst mode.

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Comparison DataSheet

Image FormatNo Compression in Color Bits ?No Compress in Resolution ?Continuous Shoot Mode Burst SpeedRaw Sensor Resolution (A7M4)Output Image Resolution (A7M4)Color Bit & File Size in Single Shoot ModeColor Bit & File Size in Continous Shoot ModeFile Size (A7M4)
Uncompressed RawYesYes≤ 6 shot / second7,008 x 4,672 = 32.7 MP7,008 x 4,672 = 32.7 MP14 bits14 bits≈ 65-70 MB
Lossless Raw (L)YesYes≈ 6 ~ 7 shot / second7,008 x 4,672 = 32.7 MP7,008 x 4,672 = 32.7 MP14 bits14 bits≈ 40-45 MB
Compressed RawNo (12bit in Continuous)Yes≈10 shot / second7,008 x 4,672 = 32.7 MP7,008 x 4,672 = 32.7 MP14 bits12 bits≈ 35-40 MB
Lossless Raw (M)YesNo (14.2 MP)≈ 6 ~ 7 shot / second7,008 x 4,672 = 32.7 MP4,608 x 3,072 =14.2 MP14 bits14 bits≈ 20-22 MB
Lossless Raw (S)YesNo (8.19 MP)≈ 6 ~ 7 shot / second7,008 x 4,672 = 32.7 MP3,504 x 2,336 = 8.19 MP14 bits14 bits≈ 15 MB

You can also find this data sheet at: image-format-a7m4.csv

Reference