When Moses brought those tablets down from that hill did he by chance bring down a tablet that explains pixels and file and image sizes. Every time I think I understand this stuff you guys change the answer.

Today I stood on a sidewalk and took two pictures of the same building, one portrait and one landscape. You guessed it - the file size on the landscape image is 323,000 bytes and the portrait image is 150,000. I notice the same thing when I rotate landscape images to portrait using photoshop. My guess is that all of the pixels settle to the bottom of my camera when I hold it in portrait mode and that Photoshop is just emulating my camera. Am I close?

-- bill (this_old_house@pobox.com), August 05, 2000

Answers

Well I'll bet you were using a JPEG compression mode, weren't you? JPG compresses different images to different degrees, and the vertical view is a different image than the horizontal view. Try it next time in TIF (uncompressed) mode.

"Sinks to the bottom"? Ooo you're cute! Best laugh out of these forums in months!

-- jeffrey behr (behrjk@uswest.net), August 06, 2000.

Yup, he brought down a tablet concerning digital, but it was a graphics tablet and curiously enough nobody could find a driver for it... What'd ya think they were doing in the desert for 40 years... lookin' for a Falaffle Stand?

Ba-Dum-Bum! But, seriously folks... ;-)

I, also, would suggest it might be in the compression algorithm. Perhaps something to do with the way the algorithm scans across the image(from left to right), as a (human)viewer would?

I have a few questions in return. Was the building on a lot by itself? Did the portrait shot just catch the one building and the sky behind it, or just the building? Did the landscape catch other buildings that wouldn't compress as well as sky might?

Or could it just be that PS, at the setting you have it at, just uses a different level of compression in saving the image than the one directly pulled from the camera? I'm assuming that what you're actually saying is that you pulled the portrait image into PS, rotated and then resaved it -and it THEN had a smaller file size, after resaving... ;-)

-- Gerald M. Payne (gmp@surferz.net), August 06, 2000.

Well, I'm just going to shake my camera before I use it ;-)

-- Eileen Morrisot (meand2rays@juno.com), August 06, 2000.

Thank you for all of your help guys but Eileen had the correct answer. I tried shaking the camera before each image and I got a consistent 100 byte image while the focusing motor played Hail to the Chief" as an added bonus

I shot the two images with a Nikon 990 set on XGA Fine and I'm sure there will be a collective "aha" when I tell you that the building, a courthouse, has a huge tower on it. The first image was all building sans tower and the second included the tower and two big dallops of sky so those of you who included mention of compression, algorithms etc will get extra credit - but I still think it's weird. Digital photography is like god - "It works in strange ways".

-- bill (this_old_house@pobox.com), August 06, 2000.

It's a new feature of digital cameras..."bottom-weighted" metering.

-- Scott J. Little (scottjl@earthlink.net), August 06, 2000.

One of the most important things you can learn is that these pesky pixels often have a mind of their own!

-- fred (fdeaton@hiwaay.net), August 06, 2000.