7D Pics show at 72 dpi v Sony A77 show at 350 dpi on Laptop

Hi can anyone explain that to me.
OK the Sony card was put in the Sony Vaio's internal card reader and it is 24 mps

and the Canon card [Sandisk Extreme] was read by a Sandisk Imagemate card reader [nb this reader is unsupported in Win 7, but works with a generic driver - could that be an issue?]

Both are then just opened on the 16.4 Premier Full HD Plus 1920 x 1080 60/50/25/24p laptop screen.

Q. why is the Sony photo at 350 dpi and the Canon at only 72 dpi. Yes I'd expect the 18 mps image to be less dpi but why such a large difference. The DPI says its horizontal and vertical resolution.

I'm just trying to compare pics taken with the old A77 and the new 7D sadly most of the pics I took in March with the A77 are circa ISO 1600 and the 7D taken today are 100 to 400 ISO - so maybe thats not fair?

Also how does one post an image on this forum in high quality i.e. for other members to look at in order to technically appraise them i.e. to see what am I doing wrong; when the forums upload max filesize is only 150 KB and my images are either 6.7 MB [Canon] and 9.21 MB [Sony] respectively. You guessed I'm new to this stuff.
What I want to do is put up a couple of pictures taken on the new 7D and ask are these as good as it gets or is my technique way off, and is the new camera and lens OK.

dpi is just an exif tag value. its utterly meaningless when viewing on a screen.

Sony and Canon have each chosen to embed different default numbers into the usually meaningless DPI field within the EXIF.

If both images are posted to the web, the viewer merely scales the images down, so that the computer monitor is filled with the image. Depending upon the total pixel count of the image vs. the pixel count of the monitor, that might result in viewing an image at 27% from one camera vs. 32% from the other (fictitious numbers that I use only for discussion of concept).

There is a pixel count limitation for POTN. POTN has a maximum number of 1024 x 1024 pixels for any image posted, so you need to use a post processor to resize the original image to have fewer than 1024 pixels in each direction, and post a link to that resized version of the photo.

Yeah, it has no significance whatsoever unless you are printing out and use it to define the print size. The images don't "show at" either value, they are a fixed size in pixels and display on your screen at 1 pixel in the image to 1 pixel on the screen in both cases, or whatever the software scales the image too.

You can simply change it and put in 300 dpi or 1 dpi and the image on your screen, and the file itself will look exactly the same. Canon use 72 dpi as the tag because it is an "internet standard", sony use 350 dpi for some other reason, probably because it is a good number for printing from. It makes no odds whatsoever, and you can enter any value you wish when you want to print the image, or ignore it and just click "10x8 print" or whatever and let the software place the appropriate number in the box.

Thanks guys - I was just lost as to why and what effect it was supposed to have and further confused as it didn't seem to have any effect on quality. As usual this site made me understand.

Wilt wrote in post #14603114
Sony and Canon have each chosen to embed different default numbers into the usually meaningless DPI field within the EXIF.

There is a pixel count limitation for POTN. POTN has a maximum number of 1024 x 1024 pixels for any image posted, so you need to use a post processor to resize the original image to have fewer than 1024 pixels in each direction, and post a link to that resized version of the photo.

I assume when you say "post a link to" ; you mean setup a 'hosting' account at something like flickr and download them there, and then load the link in POTN to that file?
If so looks like I have to choose one, that should be fun, me trying to choose something I have absolutely no idea about. I guess you just look for the highest resolution and the biggest file size and limits and the price?
Any recommendation for someone who doesn't really need it other than to let someone advise me on IQ; and therefore really doesn't want to spend money on it. i.e. my photos are for me and my family generally. i.e. if I wanted to share them I'd just email someone the pics.

Re Post Processors I was going to stick with the Canon one that came with the camera or my laptop a Sony Vaio comes with PMB [which my Sony A77 used].
Is the Canon one easy to use - just thought I'd stick with it as a newbie as then it's all in one camp - to avoid manufacterer conflicts - is that sensible for DSLR newbie?

Submariner wrote in post #14604840
I assume when you say "post a link to" ; you mean setup a 'hosting' account at something like flickr and download them there, and then load the link in POTN to that file?
If so looks like I have to choose one, that should be fun, me trying to choose something I have absolutely no idea about. I guess you just look for the highest resolution and the biggest file size and limits and the price?
Any recommendation for someone who doesn't really need it other than to let someone advise me on IQ; and therefore really doesn't want to spend money on it. i.e. my photos are for me and my family generally. i.e. if I wanted to share them I'd just email someone the pics.

Many of us simply set up an account with Photobucket. No need for a 'pro' status, the basic account is all you need.
Once you set up an account, then you 'Upload' and specify which file on your computer to upload. After you upload the file, then click on the 'IMG Code' to copy that into code your clipboard, and paste that code into your POTN message.

Just make sure that the file which you upload is no larger than 1024 x 1024 pixels...to stay within POTN limitations.