[frogoutofwater]

This might be (probably is) a dumb question, but what's the best way to resize a photo to submit to a photo contest, in order to maximize image quality while meeting the specs for image size. Currently, I use LR 5 and PS Elements 10. When I resize a photo (usually just for uploading to dropbox or posting), I usually do it in PS and start by adjusting the length of the longest side and seeing what the result gives me in terms of maximum file size and if the file size is still too big, then I adjust the compression. But I'm not sure that's the best technique to produce a high quality image. I know that there are options in LR 5 to specify the length of the longest side and/or maximum file size. I've had no trouble with the former but I have had some weird results with the latter.

For example, here are image specs for a contest:

8-bit JPG files
72 ppi
Longest side about 1280 pixels
RGB color space (sRGB or Adobe RGB is fine)
not greater than 2MB

Sometimes you see specs that call for a minimum longest side length (e.g., at least 1280 pixels). And sometimes the specs mention a compression quality (e.g., max 8).

What steps should I take, in which sequence, to prepare the image for submission?

Thanks

[Miguel]

Use LR to output a jpeg at 1280 pixels on longest side. Set the output size to 2MB. You can tweak the quality settings for the size requirement. Go with sRGB to look good on any likely monitor. Ignore the 72 PPI requirement. It is meaningless. I hope the judges are smarter than my perception based on their specs.

M

[Na Horuk]

I would use LR and in the export wizard I would simply input those values: 72ppi, 1280 longer side. And highest quality. Then I would look at the exported jpeg to make sure its under 2MB. If its above 2MB, I would delete the jpeg, adjust compression and export again. In jpeg, some photos will be much bigger than others, depending on how easy the content is to compress.

[reed_page]

Normally I use Irfanview for the resizes, ppi color and size limitations of an upload or a contest.
Resize allows you to to make the longest side 1280 and keep aspect ratio
Also in resize it has ppi adjustment
In Decrease Color Depth it will allow the decrease color depth to 8-bit jpg
While Saving it will let you specify max size.


Order would be
Resize/ ppi adjust
Decrease Color Depth
Save as Max size


Hope this helps.

[johnyates]

I resize in steps, usually by 50% at a time, till I get close to target resolution. For instance, to take a K5 file down to 1000px across:

4928px => 2464px
2464px => 1232px
1232px => 1000px

I do this in Photoshop, and for the first reduction I specify 'bicubic sharper'. For the second reduction, I specify 'bicubic'. For the third reduction I choose either 'bicubic', or 'bicubic sharper', whatever looks best.

If you have a file size limitation, adjust your quality level to get the biggest file size allowed (highest quality/least compression) when saving.

Whatever you do, you *don't* want to have your image reduced by an algorithm on a web page.

[frogoutofwater]

These are all very helpful suggestions. Thank you very much for the quick responses - I'll experiment a bit more.

[jlstrawman]

Normally I use Irfanview for the resizes, ppi color and size limitations of an upload or a contest.
Resize allows you to to make the longest side 1280 and keep aspect ratio
Also in resize it has ppi adjustment
In Decrease Color Depth it will allow the decrease color depth to 8-bit jpg
While Saving it will let you specify max size.

+1 to Irfanview. Used it for many years. One of the very best free viewer / editors.

[Adam]

I'm not sure if this is part of Lightroom or not, but the scaling (resampling) algorithm you use is also important. Bicubic, which is the Photoshop default, tends to sharpen details as you scale the image. This is great for nature images and images without fine details, but can result in photos that look over-sharpened at times. Refer to the examples below to see what I mean.

1. Here, bicubic is better because it brings out fine details in the flower, but it also takes away from the smoothness of the petals by sharpening pollen, etc.

Bicubic:

File Date

View Picture EXIF

Bilinear:

File Date

View Picture EXIF

2. Here, the simpler bilinear algorithm is better because it does not over-sharpen the rocks and fence.

Bicubic:

File Date

View Picture EXIF

Bilinear:

File Date

View Picture EXIF

I've found that bilinear is also best for landscapes with distant objects and just about anything containing text.

[Miguel]

Lightroom uses an adaptive sampling method which combines bicubic & bicubic sharper algorithms for downsampling. Has always provided better results for me than when using Photoshop.

M

[Adam]

Lightroom uses an adaptive sampling method which combines bicubic & bicubic sharper algorithms for downsampling. Has always provided better results for me than when using Photoshop.

M

Is it more advanced than using bicubic sharper for reductions and bicubic smoother for reductions? It would be nice if it could resample different parts of an image in the most suitable way.

[Miguel]

Is it more advanced than using bicubic sharper for reductions and bicubic smoother for reductions?

It is according to Jeff Schewe who has had many hands in the development of both Photoshop and Lightroom. He says the amount of the three Bicubic variations used is dependent upon the amount of sampling being performed. I don't think LR is smart enough to do a frequency analysis upon the content.

M

[Adam]

It is according to Jeff Schewe who has had many hands in the development of both Photoshop and Lightroom. He says the amount of the three Bicubic variations used is dependent upon the amount of sampling being performed. I don't think LR is smart enough to do a frequency analysis upon the content.

M

Fair enough, I suppose even that approach should be able to suppress the over-sharpening artifacts. Those are pretty easy to detect using image processing algorithms.

[Miguel]

Fair enough, I suppose even that approach should be able to suppress the over-sharpening artifacts. Those are pretty easy to detect using image processing algorithms.

Good concern, but this is where LR is smarter than PS. Unless you (the user) choose one of three levels of output sharpening, the resize is very clean--soft-ish to some. I like that subtle nature of LR.

M

[mtux]

And there's a sharpening option in LR export dialog, what does that do!? I never used it.

[Miguel]

And there's a sharpening option in LR export dialog, what does that do!? I never used it.

It performs output sharpening on the image according to your requirements. This is based on the three-phase approach to image sharpening proposed by the late Bruce Fraser. Lightroom incorporated this approach in its architecture.
A simple Google search will lead you to more.

M