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DPChallenge Forums >> Photography Discussion >> Best file size for DPC challenges
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 09/23/2013 10:11:56 AM · #1
I've been typically using 799 x 599 pixels at 72 dpi for my challenges. I want to try and retain as much IQ as possible. Should I be using another size or is this fairly typical?
 09/23/2013 10:20:15 AM · #2


The BEST size would be 1,600 pixels on the longest side and less than 1MB fiLe size.

But Langon won't for some reason inscrutable to the mere mortals around here increase it
 09/23/2013 10:29:52 AM · #3
Pretty typical. I use 800 pixels on the long edge and the short edge is determined by whatever crop suits the composition the best. I use the least amount of compression that will fit under the 300k limit.

Message edited by author 2013-09-23 10:30:24.
 09/23/2013 10:31:56 AM · #4
I'd say it's in the "typical" range; a lot of folks also just do a square crop so that they can use the full 800x800.
Also note that:
- You can use the full 800px, no need to do 799
- You need not worry about setting DPI, that has no meaning when displayed on a screen (or rather, it is determined by the screen, not your setting)
 09/23/2013 12:04:14 PM · #5
Hey that was very helpful Yo_Spiff, Dr.Confuser and the always helpful Kirbic. Appreciate it!
 09/23/2013 12:07:16 PM · #6
Just a quick word here for resizing technique.

I personally like to go 2x final size, get everything superbly sharp and clean, then go to final size (4 pixels to 1 pixel), then hit it with a final light touch of sharpening at like 0.2 radius.
 09/23/2013 12:14:34 PM · #7
Hmm I always just do all my processing on the original then resize as the very last step before uploading. I have always wondered if the image was suffering from doing all the processing before resizing but I do like to have a high res version of the final image too so this work flow achieves that.
 09/23/2013 12:19:15 PM · #8
Originally posted by P-A-U-L:
Hmm I always just do all my processing on the original then resize as the very last step before uploading. I have always wondered if the image was suffering from doing all the processing before resizing but I do like to have a high res version of the final image too so this work flow achieves that.


I do this as well, but then once I resize to 1600px long edge, it inevitably needs some touchup at that size.
 09/23/2013 12:33:18 PM · #9
always work on original size then sharpness and blurs on the 800 version
 09/23/2013 12:37:33 PM · #10
I think the argument against larger file sizes before was due to user being worried their photos would be lifted and used illegally - and that has happened a few times from this site - only the other day I found a book for sale on Amazon that used one of my ribbon winner as its front cover! God knows how they upsampled that to a decent quality?!?

However I would like to see image sizes increased again, but don't think it will happen - my views on `why` that is have been expressed elsewhere onthe site and need no further discussion. But yeah, some of the work here deserves more screenspace to really shine.
 09/23/2013 01:20:49 PM · #11
Most of my images are 704 pixels on the long edge (not counting any added border) for two reasons; it is exactly 1/4 of the original size, which I think helps preserve detail by not using computations involving "fractional pixels", and, by being slightly smaller than the maximum size, I can usually save at a higher JPEG quality level while remaining under the allowed 300KB limit.
 09/24/2013 10:23:19 AM · #12
Originally posted by GeneralE:
Most of my images are 704 pixels on the long edge (not counting any added border) for two reasons; it is exactly 1/4 of the original size, which I think helps preserve detail by not using computations involving "fractional pixels", and, by being slightly smaller than the maximum size, I can usually save at a higher JPEG quality level while remaining under the allowed 300KB limit.


That makes a lot of sense to me GeneralIE. I think I'll do that next time. Thanks.
 10/12/2013 12:46:57 PM · #13
help!
sorry gang but for some weird reason my 800X700 goes way over the 300kb. I even went to the ancient tutorial and checked all the right boxes and all. I had to go to 590 to get it under 300, THEN I finally get a green light submission only to get a warning that my images is significantly undersized.

any ideas?
many thanks,
jim

10/12/2013 12:53:31 PM · #14
Sounds like you have an image with a ton if fine detail. If you'd like, you can e-mail me the one that is oversized, and I will take a look. Use the address in my profile.
 10/12/2013 01:59:36 PM · #15
Originally posted by GeneralE:
Most of my images are 704 pixels on the long edge (not counting any added border) for two reasons; it is exactly 1/4 of the original size, which I think helps preserve detail by not using computations involving "fractional pixels", and, by being slightly smaller than the maximum size, I can usually save at a higher JPEG quality level while remaining under the allowed 300KB limit.

Resizing so that both dimensions are multiples of 8 should also help. Haven't actually tried, but it would make sense.
 10/12/2013 03:07:45 PM · #16
Originally posted by George:
Originally posted by GeneralE:
Most of my images are 704 pixels on the long edge (not counting any added border) for two reasons; it is exactly 1/4 of the original size, which I think helps preserve detail by not using computations involving "fractional pixels", and, by being slightly smaller than the maximum size, I can usually save at a higher JPEG quality level while remaining under the allowed 300KB limit.

Resizing so that both dimensions are multiples of 8 should also help. Haven't actually tried, but it would make sense.

Yes, we are working in binary, so 1/2, 1/4, 1/8 ... the same goes for viewing on screen ΓΆ€” view at 100%, 50%, 25%, etc. for best/clearest detail.
 10/12/2013 03:56:17 PM · #17
Originally posted by kirbic:
Sounds like you have an image with a ton if fine detail. If you'd like, you can e-mail me the one that is oversized, and I will take a look. Use the address in my profile.


yup, very detailed - for the "textures" challenge and team thing. they would kill me if I started mailing it about. will try the 8's thing if my math teacher from 50 years ago can be found. *?*
thanks,
jim
10/12/2013 04:08:51 PM · #18
Originally posted by GeneralE:
Originally posted by George:
Originally posted by GeneralE:
Most of my images are 704 pixels on the long edge (not counting any added border) for two reasons; it is exactly 1/4 of the original size, which I think helps preserve detail by not using computations involving "fractional pixels", and, by being slightly smaller than the maximum size, I can usually save at a higher JPEG quality level while remaining under the allowed 300KB limit.

Resizing so that both dimensions are multiples of 8 should also help. Haven't actually tried, but it would make sense.

Yes, we are working in binary, so 1/2, 1/4, 1/8 ... the same goes for viewing on screen ΓΆ€” view at 100%, 50%, 25%, etc. for best/clearest detail.


I cant figure it out. came up with 412.5 (1/8 of 3300 pixels)- that is even smaller than what got me below the 300 magic number but got the warning that it was really small.

this sucks - I must enter before tomorrow night.

anyone?
thank you
jim
 10/12/2013 04:09:32 PM · #19
While resizing on even powers of 2 is a good practice, it won't help with getting the file size down. In fact, if it results in more fine detail, it could hurt.
The only way to reduce file size for a given level of detail is to increase compression (reduce JPEG quality setting). Doing this is almost always preferable to reducing the image pixel size. In other words, better a little lower quality pixel than none at all.
 10/12/2013 04:25:12 PM · #20
Originally posted by oldbimmercoupe:
Originally posted by GeneralE:
Originally posted by George:
Originally posted by GeneralE:
Most of my images are 704 pixels on the long edge (not counting any added border) for two reasons; it is exactly 1/4 of the original size, which I think helps preserve detail by not using computations involving "fractional pixels", and, by being slightly smaller than the maximum size, I can usually save at a higher JPEG quality level while remaining under the allowed 300KB limit.

Resizing so that both dimensions are multiples of 8 should also help. Haven't actually tried, but it would make sense.

Yes, we are working in binary, so 1/2, 1/4, 1/8 ... the same goes for viewing on screen ΓΆ€” view at 100%, 50%, 25%, etc. for best/clearest detail.


I cant figure it out. came up with 412.5 (1/8 of 3300 pixels)- that is even smaller than what got me below the 300 magic number but got the warning that it was really small.

this sucks - I must enter before tomorrow night.

anyone?
thank you
jim

No, I meant the final dimensions should be divisible by 8 because jpeg files are divided into 8x8 blocks. So an image from my camera that starts out at 3008x2000, resized to 752x500, should be cropped to 752x496. Cutting 4 lines from an image 500px wide should have a bigger effect on file size than cutting 4 lines from an image 501px wide. Again, just theory here.
 10/12/2013 04:50:02 PM · #21
Originally posted by kirbic:
While resizing on even powers of 2 is a good practice, it won't help with getting the file size down. In fact, if it results in more fine detail, it could hurt.
The only way to reduce file size for a given level of detail is to increase compression (reduce JPEG quality setting). Doing this is almost always preferable to reducing the image pixel size. In other words, better a little lower quality pixel than none at all.


I kept reducing the quality as you suggested and each time still ended up with the exact same file size of wellover 500. that aint it. crap.
thanks for your suggestion.
jim

10/12/2013 04:55:24 PM · #22
Originally posted by oldbimmercoupe:

I kept reducing the quality as you suggested and each time still ended up with the exact same file size of wellover 500.


Something isn't right. You should be able to crunch it way down, no matter how much detail is there.
 10/12/2013 05:01:56 PM · #23
Upload the full-size file to your workshop and PM me a link. I'll take a look at it.
 10/12/2013 05:31:00 PM · #24
Originally posted by George:
Upload the full-size file to your workshop and PM me a link. I'll take a look at it.

Ditto. Something's way off here. Let me resize it for you and see what happens.
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