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Comment by walshemj | Hacker News Reader

Most professionals will scrub the meta data from images as part of the image optimization process - smaller images faster sites.

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Really? I've seen metadata scrubbed for privacy reasons, but never for size reduction. And realistically how much is saved in proportion to the image size?

Imgur and Craigslist specifically scrub EXIF metadata (EDIT thanks to /u/user24) for privacy.

- for privacy

Thank you. Edit made. Need moar coffee.

Which, sadly, also reduces the chances of finding who actually produced a given photograph. TinEye and Google Images can help, but, it can be surprisingly difficult to locate the actual origin of a given photo.

(Let alone Tumblr and their infinite vortex of "reblog", which leads to more than a few dead ends)

Every little helps - Photoshop save for web can give you some quite usefull reductions I shaved 1 second of some key pages on kelley search just from optimizing a single image.

"Every little helps"

but, does it? i mean it sounds like we're talking about taking a few bytes off a probably Xmb or XXmb image.

Depends on the app. Multiply larger size x1000s of images, x1000s of visitors, x days. For offsite backups, 2x the storage cost. My general rule is, any image over 40k is too big for a web page, unless your website is about photography/high-resolution imagery. And I hate jaggies and compression artifacts as much as anybody ;-)

One megabyte is huge for a web image. That's essentially a full-screen 4K/UHD version of a highly-detailed image with no detectable compression artifacts (where "detectable" means "image subtraction doesn't count; zoom in tight and use your eyes") when run through a good optimizing utility. That's good enough for a better-than-acceptable (not optimal, but from a pace or two away most people wouldn't notice) tabloid/A3 print without uprezzing. And there is enough data to support substantial uprezzing before the image goes wonky for those inclined to do so.

Now, yer average pro doesn't tend to indulge in the pixel-peeping game (except in private, with the lights down low and the door locked, and always washes his/her hands afterwards), and tends to be reluctant to give away images that can still sell - or at least would prefer it if people kept their own Photoshop/Gimp chocolate out of their personal peanut butter. Even when the images are offered as freebies, there is no reason to force a viewer to download more than they need to make decisions; the hi-rez image will sit behind a link, to be opened at the viewer's discretion. The back button hurts everybody.

who said anything about reducing the filesize by a megabyte? i assumed the EXIF data was maybe a few kb.

not sure why i'm being downvoted. i get it, "every little bit" adds up. but here in the real world removing the EXIF data to save bandwidth is a micro optimization 99% of the time.

The grandparent meant that you wouldn't be removing a few kbs from "a probably Xmb or XXmb image", since web images aren't that large.

You're right that it doesn't make sense to downvote you for that; it was an interesting question.

This is one of the optimizations mod_pagespeed makes by default: https://developers.google.com/speed/pagespeed/module/filter-...

There's not usually much EXIF text but it isn't gzipped so it's more expensive than need be. This is the kind of tweak that's not really worth doing on its own but when you're already optimizing the image you might as well do this too.

It's not about the text, but usually the EXIF also contains a thumbnail (for faster display on the camera) that can take tens of KB.

And some images also contain a color profile as metadata -- which can be quite large.

It can make a huge difference.

    `convert from_camera.jpg -resize 200x200 resized.jpg`
    `exiftool -all= resized.jpg -o resized-exif-stripped.jpg`
    
    from_camera - 2.4M
    resized.jpg - 33K
    resized-exif-stripped.jpg - 16K

In this simple example, the EXIF data double the file size of a 200x200px thumbnail.

Is that number from ls(1) or from du(1)?

ls -h

I'd expect most content management systems will do this, but there's tons of exif data hanging out on the Internet.

I thought professionals would be more likely to add in exif data for copyright information.

The copyright and contact fields are usually the only ones not empty. The rest are pretty much irrelevant except to the magical thinking crowd. (Those are the people who believe that a particular camera, lens, or aperture/shutter/ISO combination will result in the "same" picture or the "same" image quality. For the most part, the fact that the photographer happened to be holding a D4, a 1DX or an 80-MP Phase One at the time doesn't mean the shot would have been substantially different - at web sizes, at least - from what an entry-level DSLR/MILC or even a decent point-and-shoot would have rendered.) Where provenance matters (particularly in things like the WPPA "Photojournalism" competition division) only the raw file counts. When the piece is part of a tutorial or "how I shot it", the actually relevant and helpful data appears separately as body text with an explanation.

The rest are pretty much irrelevant except to the magical thinking crowd. (Those are the people who believe that a particular camera, lens, or aperture/shutter/ISO combination will result in the "same" picture or the "same" image quality.

I wouldn't go quite that far: some people see a cool shot and wonder how it was created and how the techniques used to create it might be applied elsewhere, much as someone might see a nifty piece of software and want to see the source code.

They usually don't look at the important things (most of which is never recorded in EXIF), like where the light is coming from, whether or not reflectors or external (usually non-TTL) flash were used, and so forth. Beyond "wide" or "narrow" (for the sensor format and focal length), the aperture is rarely critical; the same applies to "slow" and "fast" shutter speeds. Both of those can be derived by eye, and if they add up to "not enough light", then there must have been a higher ISO in use. And I'm rather hoping that some day people will figure out that distance controls perspective and focal length merely changes the framing. (Fisheyes being an exception here, but they're sort of easy to spot. And Scheimpflug corrections are not EXIF-compatible.) The actual numbers don't particularly matter, and are highly situational.

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