Resolution vs. size: what am I missing?

Good morning everyone,

What a great forum! Just got my G6 few days ago and now it’s time to play Since I am new to DP, I have some questions that I’d like to get out of the way first.

After some reading, and more reading, and processing of what I read, than more reading and more thinking I came to this conclusion:

The mega-pixel rating of the camera isn’t necessarily an indicator of the quality of the image that a camera is capable to produce if we don’t know its resolution.

Here’s an example:
Camera A will creates a largest 6MP image (3000 pix X 2000 pix) at resolution of 300 dpi will produce a 10’ X 6.7’ print

Camera B that creates a largest 9MP image (3600 pix X 2500 pix) at resolution of 150 dpi will produce a 24’ X 16.7’ print.

The quality of the image from the Camera B is half of what we get from Camera A.

In order to increase the quality of the image B, we can increase the image PIXELS-PER-INCH from 150 to 300. This will produce a smaller print size (due to the fact that pixels are closer together): 3600/300 = 12’; 2500/300 = 8.3’

So, we increased the image quality which resulted in 12’ X 8.3’ print from 9MP camera B. This is NOT that much bigger than the print we had from the 6MP camera A.

Is this correct or am I waaaay off? If so, why don’t we hear much about image/camera resolution as much as we hear about its mega-pixels????? Flame suit is on, so FLAME ON :~)

Thanks!

First, very few cameras really advertise the pixels/inch used in printing - that's properly a function of the printer and the software. Second, your camera B is capable of producing a print that's 50% areally bigger than camera A. That's really more than you're giving it credit for. Third, the race for the megapixels has successfully moved into the marketroid's arena. They're convincing everyone that more megapixels is better, even though 90% of users are never going to pass 8x10 print size and unless/until they start using larger (areally, not MP) sensors in the consumer market, they've reached the point where they need to make significant improvements in the electronics to avoid the problems associated with timny sensor sites.

I Think this will clear things up , DPI = Dots Per Inch. Sure you can print a 9 Megapixel @ 150DPI and get a larger print, but a 6 megapixel @ 300 DPI when you compare the two close up, will seem much sharper or have more details to it. But if you printed both a 9MP and 6MP at 300DPI, the 9MP printout size will be slightly larger, and both will seem equal in quality.

Camera A: 10 X 6.7 = 67 square inch print
Camera B: 12 X 8.3 = 99.6 square inch print

Like Jon said - 50% more area for camera B

Tom S.

Thanks for the feedback everyone!

I don't disagree.

However, I still think that image size should go hand-in-nahd with resolution. Atleast during the review. Otherwise we'll be comparing aples and oranges when looking at two cameras that have identical MP ratings, but produce images of different resolution.

am i rite for the conclusion?,
shoot in raw and set the higher resolution can solve this problem..

If they have the same MP rating, they essentially do have the same resolution. The PPI setting the camera reports in EXIF is basically unused by anything. If a reviewer cites output size at two different pixel settings for two different cameras, that says more about the reviewer than the cameras.

A Camera does not take a picture with a resolution. It has a sensor with a fix amount of pixels and stores the image with no imformation about the later printed size.
The resolution of the print only depends on your choice of the printed size. If you choose a small print, the resolution will be high. If you want a large print, the resolution will be lower, because the number of pixels is constant.
If any camera automatically produces a resolution when it is printing direct to a printer, then this may only be a setting that possibly could be changed.

Greetings
Helmut

This is interesting:

Compare EXIF data from the shots taken by G6(7MP) and Nikon D70 (6MP) : the D70's EXIF shows 300 pixels; the G6's - 180 pixels.

As far as EXIF data, I guess resizing in PhotoShop may shine more light on this issue (for me at least).

Yeah, but they'll display on your screen at 72 PPI (or 96 on high-res) regardless. Like I said before, the PPI setting in your EXIF data is essentially unused by most apps. My D60 and A80 report 180 PPI, my 20D reports 72 DPI. But when I go to print out an 8x10, guess what? They all print a full 8x10. It's meaningless.

THANK YOU! This is what I was after. The buttom line: JUST PRINT THE DAMN THING

Well... look at it this way:

- An image of a square that prints 6"x6" @ 300 ppi shows up as 1800x1800 pixel resolution.
- An image of a square that prints 3"x3" @ 600 ppi ALSO shows up as 1800x1800 pix resolution.
- An image of a square that prints 12"x12" @ 150 ppi, again, shows as 1800x1800 pix resolution.

This doesn't negate the fact that there are 1800x1800 = 3.24million pixels in all 3 images. The resolution is one of the only constants (if not THE only) in determining how much detail/data exists in an image.