Originally posted by Skodadriver I am curious about the file sizes of the images.
Is the "resolution" of a lens reflected in the file size? Larger = better?
Or are there other variables between lenses including actual FL (i.e <28mm or >28mm) or possible lack of infinity focus as has already been mentioned in this thread or centre and edge performance variables?.
Is the camera sensor in this test "under-resolving" what the lenses should be capable of?
Perhaps I should have posted this in the beginners help section but as this test is being done and evaluated I have posted it here.
Many thanks for doing the testing and for any answers.
JPEG is a image file compressed by keeping the least amount of information about the image that captures the strongest visual details in the image.
To a first approximation, the size of a JPEG file for a given value of the JPEG quality setting (e.g., 3-stars), is a function of the amount of detail in the RAW sensor data of the scene. The greater the amount of variation in pixel-to-pixel brightness differences, the less the algorithm thinks it can discard whilst preserving the structure of the scene.
In general, images of simple scenes, low-contrast scenes, out-of-focus lens settings, optically-poor lenses, and low-ISO be smaller than those of detailed, high-contrast, sharply focused, high ISO, with a high-resolution lens.
If the sensor underresolves the lens, the effects on file size would depend on whether the sensor has an antialiasing filter or not. If there's an antialiasing filter, then all lenses that match or exceed the sensor resolution would have similarly large file sizes. If there's no antialiasing filter (Wild Mark didn't say if the AA simulator was on or off), then file size for an extremely detailed image would continue to grow somewhat for the sharpest of the sharp lenses (because such lenses would resolve sharp details such as telephone wires, backlit twigs, or text on signs as having perfect high-contrast step-changes in brightness between adjacent pixels).
In the case of these tests, Wild Mark took pictures at the same ISO of the same scene with the same attempt at focusing the scene. Thus any differences in file size would likely come from differences in the sharpness of the lens in resolving the entire feild of the image.
(P.S. Of course, there's a bunch of technical details and clever processing by which the camera decides what information to keep and what to discard. I'm sure every camera manufacturer has their own clever tweaks for interpreting the raw sensor data and adjusting the JPEG compression to get the best looking picture with the fewest artifacts in the least file space possible. Also, I'd not be surprised if some lenses such as those with speckled, "busy", or soap-bubble bokeh can create largish files if the bokeh have a lot of details in them.)