A question about camera resolution!

[kata]

Hey, guys.
I am new here. I found this website very professional!
So I hope some one here can help me figure out what are the average level of image/video resolution?
Thanks very much!

[dje]

Hello kata and welcome. I'm not sure whether I understand your question but current still cameras have sensor resolutuons ranging from about 12MP to 36MP. I suppose the most common sizes are between 12MP and 18MP. An 18MP 3:2 format sensor has 5184 x 3456 pixels.

Most video cameras these days are full HD with 1920 x 1080 pixels which is about 2 MP.

Dave

[revi]

Hi Kata,

I think, if you want a more detailed answer, you'll have to clarify your question: if you just want to know the numbers of pixels, Dave gave you a full answer. For more details, sites like Amazon, B&H or the sites of camera producers would have more information for specific camera models.

If you are interested in what kind of details on the subject can be shown, the discussion will get more complex.

[Geoff F]

Or are we talking about actual image resolution; ie pixels per inch.

Where different cameras have various output default resolutions, although that doesn't really matter as long as the correct resolution is used for specific purposes.

Such as 72 ppi for internet use, but 96 ppi for European monitors; and 300 ppi for printing, although 200 ppi usually works fine for home printing.

[xpatUSA]

Or are we talking about actual image resolution; ie pixels per inch?

. . . such as 72 ppi for internet use, but 96 ppi for European monitors . .

Perhaps a little OT, but I keep seeing 72dpi mentioned on photographic fora in reference to the web, but the average monitor these days has something like 0.29mm dot pitch or better, i.e. 86 ppi or better. My current NEC 1990SX and my cheap HannsG JC199 are both 0.294mm dot pitch, for example.

Is the oft-quoted "72 ppi" a hang-over from the older Macs and their font sizes in 1/72nd of an inch? Or are 72 dpi monitors (0.35mm dot pitch) still commonly used?

Serious question - I really am puzzled. Even my PSE 6 defaults to 72 ppi which doesn't match anyone's printer, let alone monitor, these days, does it?

[ajohnw]

The 0.35mm pitch from memory relates to crt type monitors and colour TV's Ted. My current display is 95 ppi. I think a few get up to near 100 now.

John
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[kata]

Hello kata and welcome. I'm not sure whether I understand your question but current still cameras have sensor resolutuons ranging from about 12MP to 36MP. I suppose the most common sizes are between 12MP and 18MP. An 18MP 3:2 format sensor has 5184 x 3456 pixels.

Most video cameras these days are full HD with 1920 x 1080 pixels which is about 2 MP.

Dave

Dave,Thanks very much. I think your answer is very useful.
I am dealing with recovering some information from a still image or a video. So I might need the number of the average pixels a camera can offer,since I might deal with a matrix which is transformed from the original image. I think it might be a litter less than the number the sensor can offer .
ps, MP means million pixel?

[kata]

Thanks! I agree that Dave answered the question!

[kata]

Thanks for your answer!
I need to do image processing with the images or video.
So you meant that the resolution of a certain image or a camera sensory doesn't matter very much? I got a little confused about this since I am definite a novice in this domain. If the resolution of a image is very high ,say 30MP as Dave mentioned above, but I need to use it for internet, so there will be some mechanism automatically converting it to 72 ppi(converting it to a image with very large size but smaller ppi?)?

[kata]

The 0.35mm pitch from memory relates to crt type monitors and colour TV's Ted. My current display is 95 ppi. I think a few get up to near 100 now.

John
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I just get very confused when conversion of resolution of the same image on different device or under different circumstances.

[xpatUSA]

Hello again Kata, I've edited your post into a question and split it up a bit . .

If the resolution of a image is very high ,say 30MP as Dave mentioned above [and] I need to use it for internet, [is] there some mechanism automatically converting it to 72 ppi [or 86 or 96 or 100+ (think iPhone)]

There is indeed a mechanism, sometimes manual, other times automatic. But first, think of an image 5184 pixels wide and 3456 pixels deep, as it came out of the camera at "max resolution". Now you or someone else has to view it. But how?

A cellphone display is maybe 800px wide.
TV 1920px as Dave points out.
My computer screen 1280px
And a printer with letter-size or A4 paper approx 3000 dots wide in landscape printing mode.

So, no matter how your image is viewed, it's too big to fit anywhere unless something is done. Most people solve this problem by opening the image file in a Photo Editor which has a) the ability to manually re-size an image and save it smaller and b) automatically re-size it during printing without having to re-size the image (it gets "scaled" during the printing process).

So, now it is clear that the big image has to be either changed in size to fit on screens or your Editor has to be set up to match your printer (often "page setup" under the "file" menu). It should also be clear that for screen viewing you need a different file for each type of viewing - the classic example being a clickable"thumbnail" image and say a larger image for (in my case) a watch collection page: http://kronometric.org/tcw/

Bear in mind too that pixel resolution does not equate to image size, by which I mean that 640px on my Samsung phone is maybe 3" wide but on my computer screen is about 7-1/2".

by converting it to a image with very large size but smaller ppi?

This sentence perhaps does not mean what it says. But, as it stands, it can't really be done. Firstly, let's just use "ppi" for printer output (just to save me some confusion). The reason it can't, or maybe I should say "shouldn't", is that image pixel size and ppi are like opposites (i.e. inverse). The arithmetic says that an image 5184 pixels wide printed at 72 ppi would be 6 feet wide. (5184/72/12)=6. At 300 ppi, only 17" wide, at 600 ppi - 9", you get the idea . .

So, now if you want show a still in video - you simply (ho ho) re-size your 5184px image to 1920px wide and Bob's yer uncle!

Your next question should now be "but now the image is too tall for my TV, what shall I do?". I believe you will be able to figure out the answer to that one . . . ;-)

[Geoff F]

Attempting to continue with the resolution (ppi) issue, rather simply.

Some cameras seem to still use a 72 ppi resolution as a default setting. Which downloads an apparently massive image to your computer.

European monitors have worked at 96 ppi for many years, possibly always.

The main thing to consider, Kata, is the total number of pixels in a photo. For example 4,000 pixels on the long edge. Resolution in ppi controls how large this photo will appear when used for a specific purpose.

This means that if you want to print at 300 ppi (which is sometimes required by printing companies) some simple maths show 4,000 divided by 300 equals a print of 13.33 ins on the long side would be possible.

Unless you need to resize or crop and resize to a specific print size you don't need to worry to much about this. Many people never think about such matters. However, for some of us, getting specific sizes absolutely correct is an essential part of the editing process.

For internet use, getting an image size and resolution correct will increase the image screen quality. Most internet software and computer monitors will auto resize as necessary. But this can result in reduced image quality.

Therefore, for CinC use (uploading with the Tinypics method) I will resize my images to 1,000 pixels on the long side and a resolution of 96 ppi. This should display well on most monitors without creating excessively large files or having to go through an auto resize. Slightly different settings are also possible and used by other people.

After resizing for internet use, many of us apply a very slight extra sharpen to our photos.

Depending on your software, you may have auto settings for 'resize to internet use' or something similar which is often sufficient. However, many of us prefer to manually resize using the Image Size menu.

This may initially sound extremely complicated but is quite simple once you master the basic concept. And there are a number of articles on the internet which go into greater depth with better clarity than I can explain.

[xpatUSA]

Hi Geoff, glad that you agree with my post above. Great minds think alike! ;-)

I didn't get this bit though . .

Some cameras seem to still use a 72 ppi resolution as a default setting. Which downloads an apparently massive image to your computer.

[Manfred M]

Don't get too hung up on the ppi settings, as all this number does is defines the dimensions of the image. The only number that truely matters is the sensor resolution (height and width pixel counts); ppi just defines the size of the output at that setting. As has already been stated, when it comes to a screen, this number depends on the resolution you've set your video card to and the maximum resolution your monitor is capable of producing.

One dimension that may matter is dpi; and that is related to your printer. Canon and HP printers have a native resolution of 300 dpi, while Epson is at 360 dpi. There is some evidence that sticking to native resolution on your input results in better print quality because of the way the printer interpolates the data.

[ajohnw]

I just get very confused when conversion of resolution of the same image on different device or under different circumstances.

Basically it's effectively bit mapped to suite the device. Some how I suspect you will understand that. Software maybe. Any image can effectively be displayed on any suitable device. Generally if a printer the image will be scaled to fit the page size. Displays are a little different. Picture browsing software will generally scale an image to fit in what ever window size setting it's currently at. There will usually be an option fo also view at 100% resolution and in that case the image may be well over the size of the display so scroll bars etc have to be used to view parts of it. Images intended specifically for the web are usually reduced to a suitable size for viewing on a PC screen.

Most digital cameras these days produce images with a many more pixels than are available on a PC screen. An HD video type screen for instance is 1920x1080 "pixels", only a little over 2 mega pixels or mp. That's how software sees it anyway, The screen has the ability to map the 3 8bit colour channels to each pixel.

When you talk actual resolution things get complicated. Say a 15mp camera is used to take a picture. There may be detail in that picture that can't be reproduced on a pc screen as too many pixels have to be lost to allow it to fit full sized. The camera may not even capture 15mp's worth of detail. Much depends on the lens, it's quality and the size of the sensor. The best possible lens can only produce a certain level of resolution so taking a 10mp compact with a typical tiny sensor there is no way that a lens can make full use of them. Take a full frame dslr with 10mp and the job the lens has to do is a lot easier as the pixels are a lot bigger. Some people with a technical bent feel that 22mp is about the limit in this respect for full 35mm frame digital cameras. That corresponds to about 14mp for aps sensors and 11mp for 4/3 types. Personally I think they are taking too simplistic a view and thinking in terms of pure black and white images. You will see a link on the top of these pages to tutorials that cover many aspects of photography and what might be called the physics of cameras - how the sensor actually records and image etc. There is also lots of information on specifics on the wiki. One of the really hairy areas is just how compacts with their tiny sensors can produce decent large pictures - the answer is clever software and jpg compression - when examined carefully the detail isn't really there which if reduced to web sized shots arguably doesn't matter.

John
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[xpatUSA]

Attempting to continue with the resolution (ppi) issue, rather simply.

Therefore, for CinC use (uploading with the Tinypics method) I will resize my images to 1,000 pixels on the long side and a resolution of 96 ppi. This should display well on most monitors without creating excessively large files or having to go through an auto resize

Just to be clear for Kata's understanding, the resolution "setting" of a JPEG file does not affect it's size when viewed on a computer monitor. That is to say it will appear at whatever resolution, and therefore size, the monitor driver is set to. So if Geoff posts a picture 1000px wide and set to 96ppi (10.42" wide on a "European" monitor) - it will appear bigger on my NEC monitor's screen at 86dpi (11.63"). However, if I were to go into the Windows Control Panel and set my screen appearance to "VGA" (640x480px), Geoff's 1000px wide image would now be too big for my screen.


Out of interest, I took one of my watch images which was 512px wide and peeked at it's internal file settings (EXIF data) - the resolution was 300ppi. It appears on my screen as 5.95" wide. I then hacked into the file using ExifToolGUI and changed the resolution settings to 72ppi. On re-opening the file on-screen, it appeared just as before - 5.95" wide. So, it would appear that the image file's ppi setting is not used for normal screen displays.

Perhaps it would be used if "Print Preview" is available in an Editor? Or by a "Screen Proofing" utility? [Pardon my ignorance, I rarely print anything. It's called "Soft Proofing" and refers to applications or plug-ins that present your image on-screen but as if it went to a printer - including scaling the view to the image's ppi setting].

[kata]

Yeah, thanks for your answer.
I think I was confused about the interpolation. I agree with what you said!

[kata]

Thank you very much for the post in such detail!
I think I got it!
No wonder there are a raw image and a JPEG image produced with one camera shot. So the raw image actually consists of the sensor resolution information.

[kata]

Thank you for such detailed answer!
You guys are so kind!
I think I understand now!

[kata]

John,
Thanks very much .your post is very helpful!
I think I didn't realize the conversion of the resolution is actually combined with data loss.