Call to Challenge - Photo Experts

Okay,

For all you

Photo Experts

out there, I present to you two images of my cute daughter for comparison and analysis.

The Challenge -
Show me compression oddities that exists in the JPG(lossy) and not in the BMP (lossless), simulating a UFO picture.

The Details -

Each Image has EXIF tags. Both Photos were taken at 6 mexapixels, and then resized to 640x480. The JPG Image was saved directly off the camera as a JPEG, then the same image was re-saved to another directory straight off the camera as a BMP (as a 24bit BMP, Lossless).
Then the images were re-sized to 640x480, retaining their respective image formats.
The Camera is a Fujifilm FinePix A600.

They were then uploaded to my personal website, brokenhalo.org for dissimination.

What I'm hoping to gain by this little endeavor is a clear understanding and un-distiputed proof of oddities in image formats, so we can achieve a better understanding of hoaxed ufo photos.

I use these photos of my daughter because their are plenty of objects in the picture to use in comparison, she's a cutie, and these photos are already available publicly anyway (on myspace, etc). Please let me know if these aren't suitable.

JPEG Photo

BMP Photo

[edit on 21-4-2007 by zeeon]

It would be nice to see the attributes of the different formats hashed out. I don't really have an educated eye or much of an understanding... I do notice folks seem to favor different formats for different things.

A reference set of the various effects would be very handy.

Thanx,

Vic

Vic,

You can get a general understanding from wikipedia entries on the different image formats available.

Mainly, as I understand it, JPEG messes with certain artifacts in the picture (making it appear blocky, and possibly edited in) because of it's compression algorithms.

The argument is that is lossless (or non-compressed) images don't do this, and that if an image is in JPEG format, it's useless to use for analysis because of what it does to the image when it's compressed.

Not something I know much about, but maybe we can get some discussion going with a little reading:

en.wikipedia.org...
ai.fri.uni-lj.si...
en.wikipedia.org...
graphicssoft.about.com...
www.scantips.com...


Perhaps someone can bring in some ufo photo examples?

Well I'm certainly no expert, but fun to look into.
Hm. This would have been more fun if you had saved one of as jpeg and then as bmp

Jpeg like all non loss less formats uses compression by making approximations, various types of interpolation, and is usually easiest to catch around sharp edges between two different colors when it comes to value, brightness and contrast. You can spot the differences with the naked eye in these two images by looking for an area that is full of various bright colors, i started by looking at the wheels of the little car there since it was a bright red against a dull brownish carpet. Then the multicolored..ehm..thingy on the car.

Hm. Well to make a long story short and as to answer your questions I guess I would look for "halos" of a sort, an area close to an edge between colors and see if there seems to be small blur in between the two areas that have shades of color a to color b, a clear sign of interpolation taking place which just does not happen in a crisp lossless bitmap. Things of course gets trickier with moving objects, slow shutter or moving camera.

Tried to do some gifs here showing the interpolation, but making it a gif makes comparison even harder since I set it back to 256 colors..but oh well..






Was it something like this you were after?



[edit on 8-5-2007 by lasse]

Wow yeah!

Thanks for posting. I thought my poor thread was dead, but you have brought it back from the grave

The information you presented was very helpful. Thanks ! I sincerely appreciate the detail you took, and the animation of the gifs. I think I'm understanding the differences now. From looking at the two pictures, I couldn't see much of a difference, but after your dissection and analysis, I think I'm understanding now.

Again, thanks. If you want to clarify or go even more into detail, I'd surely welcome that also

From what I can tell you, is that jpg should be the only way to save your pictures, and never use bmp. The difference between the two, is that in the Jpg, the images are much clearer, when zoomed in about 200% compared to the bmp, which is darker, and more pixelated.

BMP is crappy format, to save any image in, except for web graphics, this goes the same for gifs. The quality in both gif, and bmp, is a lot worse, then saving images in JPG.

Theres also, methods for saving for web, which will reduce the dpi, and increase the noise in images. While if you save it the jpg at high quality, you will not see the pixelation, unless zoomed in few 100x.

In the two images, Ive zoomed in about 200% and there are more colors, and sharper images in the jpg, then in the bmp. The bmp at 200%is blurrier, and colors are lost, and is much darker.


To get an image with high quality, and even more detail, you need to leave the shutter open for a longer time, and not to use flash. So that more detail will come into the photo, which will then let you zoom in further, and still see more clarity, then in a lower res image.

Hopefully this helped, im a big photo nerd.

There are two types of image file, compressed and uncompressed.

Today's big images make uncompressed files almost useless (although some people ask for digitized A4 sheets at 600x600 dpi without compression), so most image formats today use some kind of compression.

BMP can use a type of compression called Run Length Encoding (RLE), but that method is only good for images that have large areas of the same colour.

TIFF files can use different compression algorithms, including JPEG and LZW (the same compression algorithm used by ZIP files).

PNG files use a different compression algorithm, achieving higher compression ratios that BMP or TIFF when using loss-less algorithms.

GIF files use a compression algorithm similar to LZW, I think, but are limited to 256 colours, making it useless for photos.

RLE, LZW, PNG and GIF's compression methods do not loose details or change the image in any way, when we open the image file we see it exactly as it was before it was saved in that format.

JPEG compression looses information to achieve higher compression ratios, and it also uses psychological effects to make us see colour that are not in the image, like putting a green line beside a pink line to make us see something that looks like a 3D grey line.

Also, when we use high compression ratios in JPEG, the algorithm changes so much the data that it shows the blocks of data with which it works, making those famous blocky images.


Those images posted by zeeon, if they were saved from the same file from the camera, are probably two versions of a JPEG file, most cameras use JPEG because it uses less memory to store them on the cameras. Once a JPEG always a JPEG, even if we save the image as a BMP the detail is already lost and, because BMP does not change the image, the BMP will look exactly like the JPEG, and that is what I think happened here.

Putting the two versions of the photo on a image editing program, in this case PaintShop Pro, and using two layers for the two versions and using the "difference" blending option shows the difference between the two images, and in this case the difference is a all black image, meaning that there isn't any difference between the two images.

Resizing the image also reduced any of the JPEG artifacts that may exist on both images.

My conclusion is that you had a good idea but you used the wrong data. You should use an image without any compression as a starting point. If your camera has that possibility save the photos as TIFF or RAW in the camera and convert them after on the computer.

Use Photoshop, thats it, and only that program for editing/creating images. Its pro, everything else is sub standard.

If your camera has the function of saving the images as .raw. Start using it, its much higher quality then jpeg, but the size will also increase to almost double or triple. Depending on what color setting, and other jazz your using.

Actually yeah, I think it does have the .RAW option.
I'm pretty sure it doesn't save it on the internal memory as a certain format (IE JPEG) - The program I use to save the images from the camera to the computer allows me to select the image format before being downloaded and saved on the computer.

So you guys suggest taking more pictures, saving one in raw, and the other in JPEG to see the difference?

I can do that later tonight / tommorrow. Any suggestions on a picture that would reveal the most differences?

Not all digital camera's have the raw saving option, but if you do, set it up! You'll probably need a bigger xd card to save the images. A 2 gig would be decent, if your just going to save them as raw. Just stick with jpg/raw/tiff and nto bmp, gif, png etc.. Trust me, I work in a Photography shop, so I know what im talking about.

Most new high-end digital camera's have the option of raw (olympus 510-uz, canon/nikon slrs). I still haven't worked with any raw files, but I know from discussions, that its the way to go for editing images, that later will end up being saved to high res jpg's, or tiffs.

Always keep your digi cam, at its high possibly quality in image size at max, and picture quality, at super fine, and fine. And vivid colors, and not the automatic color setting that all camera's are on. Use the manual function to explore.

Okay, well you'll have to give me to tommorrow atleast. I seem to be having technical difficulties LOL. As soon I plugged the camera into the usb port my computer reboot. and I'm running out of battery power - I'd use the AC adapter but the wifey stored it in some hidden remote location that the CIA probably couldn't find LOL, so I need to wait for her to get back.

Besides that - My Fujifilm isn't high end. I think I remember being able to save the images off the camera as .raw format. I don't know what format the camera saves the data as on it's internal memory. I looked through the options, and it only lets me select the megapixels and other options like "landscape, sports, portrait" etc - but it does have options for the shutter speed / etc.

So in short, I have no idea what format the camera saves the images too internally - i'm just fairly sure I can save images off the camera and onto the computer in .raw format.

Hope this helps

Originally posted by puhatek
Just stick with jpg/raw/tiff and nto bmp, gif, png etc.. Trust me, I work in a Photography shop, so I know what im talking about.

BMP does not loose quality but results in large files not compatible with many things, GIF is limited to 256 colours, but I do not see what is the reason for not using PNG, it is a loss-less format with good compression rates.

PNG, GIF and BMP, are formats used for graphics because of there small sizes. FOr example the ats logo on the top corner is a gif. As well as all the links to the other parts of this site. I had to learn all this when I was taking web design. Jpgs would be used for larger images, like entrance logos and photos in general.
Also, you don't see the option in digital cameras to save images in any of the 3, because the quality would not be there, like in a raw/tiff or jpg file.

And if you do have images, that show ufo's or whatever, open up your photoshop set them at 16 bit, rather then 8 bit which most digital cameras save the images as.

First of all let me say that I was mistaken when I said that both versions of the photo posted by zeeon looked the same, they don't.

What I forgot was that the difference in both images is very subtle and I should have enhanced the result of the difference between the two photos.

Here is the result of the difference between the two photos after a gamma adjustment to enhace the difference between pixels, they are all very dark on the un-enhanced result.

Originally posted by puhatek
PNG, GIF and BMP, are formats used for graphics because of there small sizes.

That depends.

BMP files are not small.

GIFs are used mostly because of animations (like in my signature) or transparency (like in may avatar, the background is transparent), but are limited to a 256 colour palette.

PNG are small and have better transparency capabilities than GIF, they can have several levels of transparency.

Also, you don't see the option in digital cameras to save images in any of the 3, because the quality would not be there, like in a raw/tiff or jpg file.

The quality of a PNG is as good as that of a TIFF and better than JPG (who always looses quality, even at its best).

I suggest you read this page and the other related pages.