300 or 180ppi?

[Sutton Warrior]

The penny is still dropping, It seems that the sensors in the average camera is either 180 pix per inch (ppi) or 300ppi. This means that regardles of the claimed XXXX million pixcels that a camera may boast, they are limited by this 300ppi figure in terms of stark quality. The XXXX million pixel figure is only releven in terms of the size of print that is practical to produce??? Most off us will only have the capabuility to print up to A4, comercial houses will produce larger if required, but do we need or use the facility??

 

This means that what we are realy interested in is the quality of a 1" square on the print?

 

The above has been promoted by reading the recent review in Practical Photography on Canon 40D V Nikon D40X, no mention of the sensor size, although sample pictures were shown, all the comparison waffle with no 'why'. Reading the mag further, this seems to be the case in other reviews, compacts, bridge or DSLR. They seem to go very general, fair enough, as one apreciates there are other issues. This 300-180ppi issue seems to be lost here as well?

 

Is it me? SW

 

PS the Nikon took the honours, just. Interesting review, especially on colour rendition.

[RobStubbs]

If the sensors are 300 ppi (seems low to me but I don't know about this) then it's the sensor size that matters - as the total number of pixels decides the final quality, not the PPI (I think). A sensor 2 x the size of another but both with 300 DPI will have 4 (2 x 2) x the total number of pixels.

 

<edit> Although by my maths to get 10 mega pixels you'd need a 10 inch x 10 inch 300DPI sensor so somethings gone awry with the maths somewhere

 

Rob.

Edited August 30, 2007 by RobStubbs

[Newt]

Does the info in BASICS OF DIGITAL CAMERA PIXELS from www.cambridgeincolour.com help out?

 

It certainly gave me a better understanding and a clue why 300ppi might offer very different photo quality in a 3 mega-pixel camera vs a 10 mega-pixel camera. I had wrongly assumed that a pixel was the same from one camera to the next but that turns out to not be the case.

 

Note to sutton-warrior - my head is now about to explode with trying to absorb all this new knowledge and it is all your fault. I was happily wandering around in a fog of pixel ignorance & innocence but you have ruined all of that.

[poledark]

Mine has already exploded Newt :) Still reading this topic, but I got lost when 100% crop was mentioned. To me, 100% means ALL of it cropped no image left at all

Den

[MrWiggly]

Thanks for that Newt.

 

Now in "Links Vault" ...

 

Wiggly.

Edited August 30, 2007 by MrWiggly

[Sutton Warrior]

Does the info in BASICS OF DIGITAL CAMERA PIXELS from www.cambridgeincolour.com help out?

 

Note to sutton-warrior - my head is now about to explode with trying to absorb all this new knowledge and it is all your fault. I was happily wandering around in a fog of pixel ignorance & innocence but you have ruined all of that.

 

Sorry about that Newt, my head is still trying to get around it in relation to what we are told, 'the more pixels, the better the quality'. However, if a sensor is limited to 300ppi or 180ppi then the basic pixels per inch is 300 x 300 = 9000 pixels in one square inch of the picture, same maths applies to 180ppi.

 

Now, on either basis, it does not matter if the the total pixel count is 3m, 6m, 10m, quality relating to the sensors 'ppi' is fixed. If your sensor is 300ppi but the total pixel count is 6m the basic printable picture size out of the camera is about 10"x8", as per my Nikon D70s, equally if the sensor were a 180ppi unit, but the manufacturers claimed 6m pixels, the basic printable picture would be nearer A3.

 

So what I am wrestling with is, all these millions of pixels means nothing if you cant cram larger quantities into one square inch of the basic image, it seems, it is fixed by the sensor size.

 

So back to my original 'dropping penny'. my Canon 640 has a sensor that allows it to take a picture with 10m pixels, but the sensor only manages 180 x 180ppi, therefore it will and does produce an enormous image on my computer which in PS Elements is reduced to 20%! I could print that image out at A3. However the image quality if I zoomed in is only as good as 180 ppi, the more pixels per inch the better the eye perceives the picture, it will become grainy much sooner than the same picture from a 300ppi sensor.

 

I'm still trying to find out if my understanding is correct, its doing my head in as well.

 

Thats not to mention all the other things that affect picture quality

 

SW

 

PS just had a glance at the site you suggest Newt, he's got it about right, ppi is the basic governing factor for quality before any manipulation or adjustment. We are being lead up the garden path on some cameras that only have a small sensor, all its producing is an enormous file to store! Few of us really want or can produce A3 prints? My humble opinion of course.

Edited August 30, 2007 by Sutton Warrior

[Colin Brett]

Newt,

How did you come across that website?

 

I live in Cambridge and hadn't seen it before.

 

I'll check it out properly when I get back home to a decent speed connection.

 

Colin

[Newt]

Google for digital ppi and it is the 3rd entry on the first page.

[Sutton Warrior]

For those that are interested, I found the first clue to the limitations of 'ppi' as follows:

 

Right click on an original unworked picture in one of your store files, a window will appear, 'General, Summery'

 

Click on 'Summery' a list will appear, if not, a button will appear; 'advanced', click on this.

 

The list will give exif type details of the picture, including 'H' and 'V' resolution at ppi

 

Then the penny dropped!

 

 

SW

[corydoras]

MegaPixels are there to catch consumers and have got little to do with the quality of the image. What counts is not so much how many pixels are on your CCD, its how big the pixels are, how sensitive they are and the quality of the lenses. Have a look at the Mars Rover imagery. All taken on a one megapixel camera, that you would NOT want on your credit card.