Mega pixel size...

[srbphoto]

OK before anyone mocks me, I know this is a nubbie question!
Everything being equal, at what point does having more megapixels for a given print size cease to matter (or become overkill)?

for 5x7?, for 8x10, for 11x 14 and for 16 x 20?

Thanks!

Scott

PS if 10 people give me 11 different answers (a common occurance on photo boards)I may pull my remaing hair out!:eek:

[David Luttmann]

It never ceases....depending upon your output size. For some people, that may be 300ppi at whatever print size.....for others, it may be 240 or less. A perfect example for me was comparing the 17mp 1Ds Mk2 at 16x24 vs 4x5 at 16x20. There was very little difference between them. Some things were better from film, other on the digital platform.

Because everyone views things differently, all you can do is make print comparisons to judge for yourself.

[Marko]

OK, here's the answer:

1. What is your print resolution? (i.e. what dpi - 240, 300?)

2. Do you crop your images?

3. What is your sensor size?

Not all pixels are created the same. The bigger (in the physical sense) the sensor, the bigger the individual pixels. The bigger the pixels, the cleaner the image and better the dynamic range. A mid-level 10MP DSLR will produce much cleaner image than the pocket digicam with the same number of pixels packed on a tiny little sensor.

Cleaner images with less noise hold well to moderate upressing.

For example, if you don't crop at all, 8 MP should be enough for an 8x10 @300dpi. You can stretch things a bit if you print at 240 dpi - that way you can crop it by about 25% and still print at 8 x 10.

So, the simplest answer is:

(Print Width x DPI x Print Height x DPI)/1,000,000 = Net MPix count

Add about 25%-50% to this figure to reach the amount of MP needed in-camera to allow for average cropping.

[srbphoto]

Marko, thanks for the formula! I think that is what I wanted.

David, sorry to piss you off. I wasn't trying to start the whole megapixels war started up again.

The only digital I do is a pocket camera for snap shots. Someone asked me to do a quick clinic on photography and someone asked me this question. I basically told them there a MANY factors involved. I started thinking about and thought there must be some sort of approximate number.

Thanks!!

Scott

[David Luttmann]

Marko, thanks for the formula! I think that is what I wanted.

David, sorry to piss you off. I wasn't trying to start the whole megapixels war started up again.

The only digital I do is a pocket camera for snap shots. Someone asked me to do a quick clinic on photography and someone asked me this question. I basically told them there a MANY factors involved. I started thinking about and thought there must be some sort of approximate number.

Thanks!!

Scott

I'm not pissed off Scott....we're OK. I just meant that for some people, 300 dpi is the minimum, for others, 200 to 240 is OK.

What must be kept in mind is that 300+ may be needed for an 8x10, but on a 48" print, you might find 180 to 200 to be sufficient. As I said, it's different for everyone.

Cheers,

[Ted Harris]

I always find the safest way to look at it is to make your original scan, assuming you are talking film, at the highest possible resolution that makes sense in terms of the capabilities of your scanner and computer. Save that as a master file and then down rez as necessary and appropriate for the final print you want to make and the native resolution of the printer.

Having said that David is absolutely right in terms of personal needs and expectations.

[Eric Leppanen]

Here is another opinion on this subject:

http://www.westcoastimaging.com/wci/page/info/FAQ/uploadfaq/printsize.html

I would take the "maximum resolution" film format ratings with more than a grain of salt, as these appear to be based on scan size rather than usable resolution. For example, most folks I know would rate the P45 digital back (39 MP) as delivering resolution very close to 4x5 film, which is a much closer comparison than 7216x5412 (P45+) versus 11859x9102 (4x5 film).

[Ken Lee]

"A mid-level 10MP DSLR will produce much cleaner image than the pocket digicam with the same number of pixels packed on a tiny little sensor."

This can't be overstated. Quality is influenced by on-board image processing as well as sensor size and lens. That's why you need to see sample images from cameras and lenses, if you want to make beautiful images. My older 4 MP Canon generally outperforms my newer 7 MP Sony, because of many factors unrelated to pixel count.

They call it "digital", but it's analog nevertheless.

[David Luttmann]

As well, keep subject matter in mind. A portrait requires much less in the way of detail than a landscape shot with lots of fine foliage.

Finally, different sensors render that detail in different ways. I prefer the way the new Pentax (Samsung) 15mp sensor produces a 16x24 landscape than the 17mp Canon does.

The variables can be limitless.

[srbphoto]

UNCLE!!! :D

I guess my original answer (there are many factors) was actually the best!

For now on my only clinics or workshops are going to be for b&W, large format photography (well, except the one I am doing on Wed). At least when you discuss those subjects it is clear cut! HA HA HA HA HA HA HA HA HA HA HA.

BTW thanks to everyone for their input. It is very much appreciated!!!!!!!
Especially since no one called me any names (think Craigslist forums) :)

Ciao,

Scott