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95,120 reputation
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bio website mattgrum.com
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visits member for 4 years, 3 months
seen 20 hours ago

Nov
26
revised How can slightly blurred photos be improved in post processing?
added 83 characters in body
Nov
25
reviewed Approve How can I tell which Instagram filter was used?
Nov
21
comment How is this effect created in Photoshop?
Push the colour temperature and fill light sliders all the way up in lightroom (or google HDR tutorial).
Nov
20
answered How much light do I need for handheld product photography in a lightbox
Nov
19
awarded  Enlightened
Nov
19
awarded  Nice Answer
Nov
14
revised Why are there so few high quality APS-C telephoto lenses?
added 91 characters in body
Nov
14
answered Why are there so few high quality APS-C telephoto lenses?
Nov
13
comment What is a “crisp” photo?
It is just a loose synonym for sharp.
Nov
13
comment How to estimate camera sensor size?
@alasin are you sure the focal length figure you have isn't in millimeters? I've never heard of it being specified in pixels before.
Nov
12
comment How to estimate camera sensor size?
There's nothing you can do if you only have the focal length in pixels. If you have the focal length in mm then you can measure the angle of view and calculate the sensor size in mm very easily.
Nov
3
comment Seeking a way for “authoritiative”, proven method to prove that two photo images are “nearly identical”?
@AndyBlankertz yes PSNR scores are meaningful in isolation - unlike the MAE the error is expressed relative to the signal.
Nov
3
comment Seeking a way for “authoritiative”, proven method to prove that two photo images are “nearly identical”?
@DVK PSNR is not insensitive to scaling, I know of no standard metric that is. So the short answer to your question would be "no". There is SIFT (scale invariant feature transform) that works for image features (lines, corners etc.) but not entire images. You could come up with a way of converting images into SIFT features and then comparing the features, but then it wouldn't be a widely accepted method, as you would have just invented it.
Oct
31
comment Does it make sense to “Expose to the Right” except at base ISO?
@Pedr With a 5D mkIII the best performance is achieved by getting as much light in as you can (by opening the aperture/using a slower shutter), and then pushing up the ISO as high as you can (without overexposing any important areas of the image).
Oct
31
answered Does it make sense to “Expose to the Right” except at base ISO?
Oct
31
comment Does simply opening and closing a JPEG file decrease image quality?
@SteveCox I opened an image in Photoshop, saved it as a JPEG quality 7, opened that JPEG and saved it as a JPEG quality 7, then repeated 5 times. I then compared the first JPEG to the 5th JPEG. What the reference implementation does is only of academic interest if the major editors all cause a decrease in quality.
Oct
31
comment Does simply opening and closing a JPEG file decrease image quality?
-1 Just done a quick experiment with Photoshop CC and repeatedly opening and saving an image with exactly the same settings does result in a different file each time, when compared to the original using a "difference" blending mode. Apparently Photoshop is not an "worth its salt". I can't speak for other editors but I'd bet money they are the same. You could write a program very carefully to avoid rounding errors when continually decompressing and recompressing an image, but there would be no point - JPEGs are not a good intermediate format, full stop.
Oct
31
comment How can I give an assitant rights to edit without having the possibility to download the image?
This question appears to be off-topic because it is about computer security and not photography.
Oct
31
answered Why is there no image noise in my webcam dark frame photographs?
Oct
31
comment Why is there no image noise in my webcam dark frame photographs?
It's probably nothing more complicated than clipping the blacks to a level greater than the noise. I highly doubt the manufacturers of the webcam developed a processor that would recognize a frame that contained only noise and process it differently.