Mb versus MP - when size really matters

The common standard of the traditional stock photography industry is the size in megabytes (MB). The value of an image in MB sounds more appealing to the customer. Nothing more tricky than that!

The common standard for (educated) designers is the size in pixels (MP) that leads to discussions about dpi, ppi etc. It is this size that tells them how large an image can be printed.

The traditional industry uses this parameter as a trick. Requiring photographers to upsample their work (enlarging image size with a software) without any concerns about the final image (which usually ends up fuzzy and blurry) is simply wrong. Because not all images can be upsampled properly and the designer can do that easily.

The size in Mb ends up very high taking huge amounts of storage and upload/download bandwidth. Think about 10MB added this way without any gain for the quality and multiply them with several hundreds of downloads. You end up wasting GBs of data and server resources for a single file! Talking about climate change and green energy programs?!

Then the designer has to downsample the image in order to use it. Because he doesn't know the original size (unless he has an EXIF data to identify the camera and find its original resolution) he is left in the dark, having to guess how much to decrease the image. Each upsize/downsize of an image brings blur therefore a sharpen filter has to be used. Which leads to more artifacts.

The size in MB (megabytes) is the physical size of the file on your disk. It has nothing to do with the size in pixels. Hilarious, because you want to estimate what you see on the screen or in print, not how much it takes on your hard disk.

The size in MB can be higher for a small fall foliage image than for a large image of fluffy clouds in the sky.

We don't forbid upsampling of images. If the camera was low in MP you can bring the image to a better level by enlarging it a little bit. You should not exceed 10-20% though, although in some cases I've seen images at a double size looking good. But always check the final result at 100% and see how the focus areas have changed!

Photoshop does a great job at this and there are software programs even more powerful like Genuine Fractals Print Pro and

Photo credits: Erik Lam.

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September 02, 2007

Achilles

Yes, Douglas, completely agree, what matters is final quality. Subjective is the "key" word here, it's no longer a matter of quality when it becomes compulsory.
And no, this doesn't happen only with the minimum size (which is denying your own entry rule anyway), it's a standard for all files. The upsize factor is a secondary thing in my article. It is the MB vs. MP discussion that really reveals the idea. Targetting MB for the sake of marketing hides the fact that any quality factor is completely ignored.

September 02, 2007

Douglas_freer

A tad naive, Fleyeing. Upsizing is compulsory to meet minimum size criteria on many traditional sites. What matters is the final subjective quality.

September 02, 2007

Fleyeing

Upsizing - even mildly - is unfair to the customer. Try to do an upsize and then a downsize back to the original. At the pixel-level, the result will always differ from the original, with any algorithm. The customer is entitled to native quality. If he wants to upsize and/or sharpen, it's his decision. You can't make eggs again out of an omelet. Whoever sells omelets on those two "other" sites is basically fooling the customer.

September 01, 2007

Photojay

I couldn't help but to comment on the upsampling. To further confuse the issue, MP is not the only factor in the quality of a print. The size of the sensor itself also plays a role. In the age of digital, what you see is not always what you get. If you purchase an 8MP P&S camera, the size of that sensor is so small, that the image comes out the same as if you took the same picture with a D-SLR at 5MP and upsampled it to 8MP, as an example-not as a direct relation-because the quality of sensors varies from manufacturer to manufacturer. A clearer example is if you look at the size of the sensor on a Canon 5D (35.8 x 23.9 mm) and compare that to a Canon 20D (22.5 x 15.0 mm) The sensor is 2.5 times larger on the 5D than the 20D, yet the MP of a 5D (12.8) compared to the 20D (8.2) is only 1.5 times more. So, assuming that the quality of the sensor materials in both CMOS sensors is the same, the shear area of the sensor will make for better pictures, allowing the 5D to be upsampled (if need be) to a greater degree than the 20D. In my opinion, it is just best to upload what you took from the camera and let the designer upsample as needed, but that is just me... :)

August 31, 2007

Rolmat

I believe no one could said it better. The example of a foliage shot against a soft cloudy sky one is quite appropriate. Don't say anything more: I have uploaded a 2000x2000 mpx (4MP) square image with a pretty dark background. Guess what: 866Kb... but still 4MP. I believe it would go the same way with a white background or other less detailed.


However, I personally try avoiding any interpolations at all. It's just cosmetic, under my point of view, or just to fill out the minimum 4MP image size. Original size is ok, even a 5% increase does NOT produce always acceptable results, especially if the original is not that good.What I sometimes do (yet just when absolutely necessary - ie. because the composition is great but the noise and grain ruin everything), it is to interpolate the image for say... 900dpi (it means 3 times the original size, if under 300dpi), and... yeah, you got many many MB, and... guess what, not necessarily 3 times the size in MB) and then work with a... poster. Again, it will always depend on the complexity degree of the chromatic spectrum. Thus, I will deal with all those noisy things and grain artifacts at 3 times the original size value, using some clone-stamping and other tools, and then, resize it back to 300 dpi.

This has been for sometime now one of the most productive ways of recovering an image (this is one of the most popular first steps among professional retouchers). At least for. Then, all you nedd is to resize it back to its native size, no matter the no. of megapixels you will be dealing with.As just one last thing, somehow a statemente, if you prefer.

Recently, I have been abandoning the original size of my camera. The best reasons, among others, is that I prefer (and maybe, just maybe, customers too) having a good 3000x2000 mpx than the original 3456x2304 (8MP) of my Canon 350D.


But back to the beggining, great, great post, Achilles!

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