Strands #248 “Strumming Right...
Quizzes & Puzzles14 mins ago
photo file size
My camera takes 8 megapixel pictures, which I don't think I need and which gobble up space on my computer. I tried reducing the size of one photo to 'medium' and 'small' sizes, via Photoshop. The three show as 2.9MB, 1MB and 646KB. And yet I can see absolutely no difference between them, even at full-pixel viewing. The image sizes remain the same (115x86cm). So what exactly have I lost by shrinking them? Anything that would reduce their effectiveness if I printed them out?
Alternatively I could reduce the file size setting in the camera before taking the photos. Would this also appear to make no difference to the finished shots?
What effect does the apparent shrinking, in the camera or on Photoshop, have? Any at all?
Alternatively I could reduce the file size setting in the camera before taking the photos. Would this also appear to make no difference to the finished shots?
What effect does the apparent shrinking, in the camera or on Photoshop, have? Any at all?
Answers
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My guess is you have reduced the DPI (dots per inch).
A digital picture is measured by so many pixels (or dots)across by so many pixels (or dots) down (1024x768 for example)
I think if you save the picture as medium and small it is reducing the number of pixels so the picture may now be 800x600 or 640x480 for example.
A digital picture is measured by so many pixels (or dots)across by so many pixels (or dots) down (1024x768 for example)
I think if you save the picture as medium and small it is reducing the number of pixels so the picture may now be 800x600 or 640x480 for example.
Personal opinion
I think you should take your pictures, and save your pictures, at the maximum setting.
After you have taken your pictures you can easily put then on CD or DVD so they are not filling up your computer.
You never know if you are going to want to print some old pictures, or look at old pictures, in the future, and it would be shame if you did not have them at their maximum quality.
We all used to think that VHS was good quality, but when we look at old VHS tapes today they look grainy and washed out.
The quality of computer screens is only going to get better in the future and it would be shame if you dug out a picture you took 10 years ago and it looked poor quality.
You will curse you did not save it at the maximum quality.
I think you should take your pictures, and save your pictures, at the maximum setting.
After you have taken your pictures you can easily put then on CD or DVD so they are not filling up your computer.
You never know if you are going to want to print some old pictures, or look at old pictures, in the future, and it would be shame if you did not have them at their maximum quality.
We all used to think that VHS was good quality, but when we look at old VHS tapes today they look grainy and washed out.
The quality of computer screens is only going to get better in the future and it would be shame if you dug out a picture you took 10 years ago and it looked poor quality.
You will curse you did not save it at the maximum quality.
yes, that's always been my thinking, VHG - why save something that's less than the best you can get it? I have on occasion sold photos to magazines and maybe someday I'll do so again. But in reality, about 12x8 inches is the biggest they're ever going to appear in print, and I wonder if 8MP is really necessary for that. Someday of course I may want to show them on some mega HD post-blu-ray screen the size of Wembley arena, but I suspect not.
As for the reduction: no, according to the pic information, each of the 3 pictures (all jpegs, by the way) is 72dpi (presumably the default when I download them from the camera) and 3264x2448 pixels (or 115.15x86.36cm). So what on earth am I losing when I 'shrink' them? Some sort of information must be lost somewhere, but what?
As for the reduction: no, according to the pic information, each of the 3 pictures (all jpegs, by the way) is 72dpi (presumably the default when I download them from the camera) and 3264x2448 pixels (or 115.15x86.36cm). So what on earth am I losing when I 'shrink' them? Some sort of information must be lost somewhere, but what?
1) You're relying on software algorithms to perform the reductions, which do introduce losses. All do this, even the ones in Photoshop.
2) You're losing information in the photos. So they won't print out the same if you were to do an A4 print for example.
3) Try printing an image out and see for yourself. They may still be good enough, at the right distance. Printing a 8MP image at 6x4 will look great, but at A1 will look less good. But at the distance an A1 photo would be viewed from, you'd see no issues (unless of course you walked up very close to it).
4) It's better to reduce the size of the images in the camera itself. If you really want to do it, that is. But if you have a compact camera, it has a small sensor that produces losses due to diffraction at a pixel level (for a compact, about 6MP is best, regardless of what the manufacturers try and convince you). In this case, where you reduce the megapixel recording in-camera, it won't help with the diffraction issues because it just reduces the area that the sensor views, so the pixels are still the same size.
My advice -- stick to the 8MP images. They take up more space, but drives are cheap. It'll be far better for you to get a larger drive, than to start shooting smaller images, or resizing after taking the photos. In a few months you may wish you had the original 8MP image.
2) You're losing information in the photos. So they won't print out the same if you were to do an A4 print for example.
3) Try printing an image out and see for yourself. They may still be good enough, at the right distance. Printing a 8MP image at 6x4 will look great, but at A1 will look less good. But at the distance an A1 photo would be viewed from, you'd see no issues (unless of course you walked up very close to it).
4) It's better to reduce the size of the images in the camera itself. If you really want to do it, that is. But if you have a compact camera, it has a small sensor that produces losses due to diffraction at a pixel level (for a compact, about 6MP is best, regardless of what the manufacturers try and convince you). In this case, where you reduce the megapixel recording in-camera, it won't help with the diffraction issues because it just reduces the area that the sensor views, so the pixels are still the same size.
My advice -- stick to the 8MP images. They take up more space, but drives are cheap. It'll be far better for you to get a larger drive, than to start shooting smaller images, or resizing after taking the photos. In a few months you may wish you had the original 8MP image.
I haven't been able to print anything out yet, fo3nix - but I can say that seeing the pictures side by side on screen, at actual-pixel resolution, they're absolutely identical. I was entirely expecting loss of information when I reduced a 2.9MB file to 646KB - lots of it. And yet there seems, on screen, to be none at all - every pixel's identical. I'm scratching my head over this one. Perhaps Photoshop is somehow reluctant to register the shrinkage I've ordered?
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