How Many pixels do I need?

[gdanmitchell]

You might try making some test prints at the different resolution settings and comparing for yourself. I think you may be surprised.

The factors that limit the size of a print you can make from a DSLR original are most often not the print resolution setting. You'll run into issues from other things (camera stability, focus, lens quality) before image resolution (ppi) limits you.

No need to accept the (often contradictory) notions of how much resolution is enough when it is so easy to test. I can guarantee that you do NOT need 300 ppi resolution to produce very high quality large prints - but rather than believe me OR assume that I'm nuts... make a print at 300, one at 240, and another at 180 and put them up on the wall and compare.

Dan

12 inches * 300 pixels per inch = 3,600 pixels.
18 inches * 300 pixels per inch = 5,400 pixels.
3,600 * 5,400 = 19,440,000

So you "need" 19.44MP.

Thank you. This was the answer I'm looking for. I'm not good with
math so I figure I'd ask.

Yeah, I know I don't "need" that much mp's to attain my goals. Just
like one does not "need" a blue ray player to watch your regular, run
of the mill, lower res DVD movie. But it IS my preference and this
is how I chose to approach it. People can go on all day explaining
to me that a 6mp camera is enough to make a nice 20x30" print (which
I believe it can), but it's not really going to change my mind anyway.

To me, it's one more notch to justify getting the 5D Mk II.

Thanks again.

--
---
G Dan Mitchell - SF Bay Area, California, USA
Blog & Gallery: http://www.gdanmitchell.com/

 

[gdanmitchell]

Don't know about you but when I look at photographs in a gallery, I
come up REAL close. I like to see small, intricate details and how
both the camera and the lens resolve it. Matter of fact, I do the
same thing with paintings.

I've inspected a number of large prints by recognized great photographers and I often get close - if the museum and the museum staff allow this. It is definitely not true that all or even most of these prints are razor sharp when you look at them from nose-length distances.

In any case, as I wrote in my previous post, the printer resolution is rarely the thing that causes the "problem" with a print that isn't sharp enough. The sharpness limit is far more likely imposed by lens sharpness/focus, camera motion, and so forth.

Dan

--
---
G Dan Mitchell - SF Bay Area, California, USA
Blog & Gallery: http://www.gdanmitchell.com/

 

[PhillipA]

The 5DII will serve you well, but understanding the issues involved
would serve you even better.

For instance?

For instance if you have an image that you would like printed at larger than 18" x 12". Using your logic, you are going to have to start looking at medium format . By understanding the "real world" situation, you may just be game enough to try a 24 x 16 print from your "measly" 21 mp.

--



No, it's true - he IS the U.S. President!

 

[Its RKM]

People mix up dpi and ppi. They are not interchangeable.

The only person who seems to be mixing up dpi and ppi is you!

Printers use dpi (dots per inch) and refers to how the ink dots are
laid on the paper.

Cameras use ppi (pixels per inch) which relates to resolution.

My epson printer prints at 1440 dpi regular photo quality and 2880
dpi max quality.

Irrespective of your Epson's dpi setting it resamples to 360 or 720ppi ONLY - and the printer driver resamples to those native printer resolutions irrespective of the ppi of the image you send it. Use the native resolution and the printer driver does not need to resample the image when you hit the print button.

If I want to print a 12x18 at 2880 dpi I would need
12x18x2880x2880=1791,590,400 ~ 1780mpx

No you wouldn't - for several reasons:

1. You are mixing dpi and ppi. To use your own words back at you "they are not interchangeable!"

2. Even though your Epson prints at 2880dpi, it only does that in ONE axis. No Epson printer that is currently on the market (or ever has been) does more than 1440dpi in the paper feed direction, and many only do 720dpi in that axis. Read the specifications for your printer, not the advertising headlines!

3. Irrespective of the number of megapixels you send the printer, the print driver will resample to 360ppi or 720ppi, in this case throwing out at least 93.75% of your 1780Mpix!

I think that if you are picky 300ppi should be your goal.

Not if you are using an Epson. 300ppi is actually close to the worst interpolation point for Epson printers, being between the integer divisions 2 and 3 of the native printer resolution (ie. 720/2 = 360ppi and 720/3 = 240ppi).
--
Its RKM

 

[Dragos Nenciu]

People mix up dpi and ppi. They are not interchangeable.

The only person who seems to be mixing up dpi and ppi is you!

Printers use dpi (dots per inch) and refers to how the ink dots are
laid on the paper.

Cameras use ppi (pixels per inch) which relates to resolution.

My epson printer prints at 1440 dpi regular photo quality and 2880
dpi max quality.

Irrespective of your Epson's dpi setting it resamples to 360 or
720ppi ONLY - and the printer driver resamples to those native
printer resolutions irrespective of the ppi of the image you send it.
Use the native resolution and the printer driver does not need to
resample the image when you hit the print button.

If I want to print a 12x18 at 2880 dpi I would need
12x18x2880x2880=1791,590,400 ~ 1780mpx

No you wouldn't - for several reasons:
1. You are mixing dpi and ppi. To use your own words back at you
"they are not interchangeable!"

2. Even though your Epson prints at 2880dpi, it only does that in ONE
axis. No Epson printer that is currently on the market (or ever has
been) does more than 1440dpi in the paper feed direction, and many
only do 720dpi in that axis. Read the specifications for your
printer, not the advertising headlines!

3. Irrespective of the number of megapixels you send the printer, the
print driver will resample to 360ppi or 720ppi, in this case throwing
out at least 93.75% of your 1780Mpix!

I think that if you are picky 300ppi should be your goal.

Not if you are using an Epson. 300ppi is actually close to the worst
interpolation point for Epson printers, being between the integer
divisions 2 and 3 of the native printer resolution (ie. 720/2 =
360ppi and 720/3 = 240ppi).
--
Its RKM

--

And when I talked about 2880dpi I was making a point that you don't match ppi with dpi I was not trying to really say that you need 2880ppi.
actually I tried both 300 and 240 and I can't see any diff.

 

[wayne58604]

Well, that depends...

When I worked for a camera store, we had several 16x20 photos that one of the employees had taken with an E1 (5.1 MP) with the 14-54mm lens. This was not printed with an ink jet, but rather by a photo lab. Would more pixels have made it even better? No, the mood of the photo would have been lost, and had the image been shot with a lessor lens, the CA and distortions would have been distracting.

We also printed a sea side village scene (Italy? don't remember exactly where) that a customer shot with a 20D. This was cropped by the customer and was printed at approximately 8x20 for a pano effect. This was a wonderful, colorful shot that could win a photo contest had it been entered (it was not, it was his personal trip record).

So, do you need 20+MP to make a large print? No, you just need proper composition, good exposure, and a good printer (done right, it is hard to beat a pro photo lab).

Wayne

 

[Its RKM]

actually I tried both 300 and 240 and I can't see any diff.

Depends on the image content, obviously, but if you have adequate detail in the image or fine repetitive patterns, such as picket fencing or rail tracks etc., then you certainly will.

There are, of course, some specific but synthetic test patterns that make the difference very obvious, but you are unlikely to see as significant a difference with real world images - they simply serve to determine the optimum settings.
--
Its RKM

 

[rhlpetrus]

http://forums.dpreview.com/forums/read.asp?forum=1032&message=29930532

--
Renato.
http://www.flickr.com/photos/rhlpedrosa/
OnExposure member
http://www.onexposure.net/

You cannot depend on your eyes when your imagination is out of focus
(Mark Twain)

 

[hunk]

4MP?

I'm sorry but more MP do show when printed large. For this example I rented a a900 Sony as the files are more detailed than my 1DmkIII files....

http://www.x32.nl/images/eos/BURKAMASKER.jpg

(5MB jpg)

I agree most photographs look great at far less MP but this print benefits from all the little details.

--
wild images and such at my website
http://www.x32.nl

 

[Richard Ceerre]

Someone will not look closer at such sized print as for a 4 x 6" or even an 8 x 12", so the dpi to use for it does not need to surpass 200.

For this case, I do for myself the following calculation to get an appropiate MP count:
12 x 18" multiplied by 200 dpi = 2 400 x 3 600
2 400 mult. by 3 600 = 8 640 000

So, 9 MP will be enough to handle a 12 x 18" enlargement.

Note that, in practice, you don't need to select or make any conversion based on this dpi value, in-camera or through software. Just use 9 MP and OK.

 

[Greg Henry]

...is almost everybody here so keen on counting blades of grass on
poster sized prints? - because this is what you end up doing with the
some above mentioned MP numbers.

------------

I don't think you're the target audience.

People making 16x20 and 20x30 art prints know that prospective
customers inspect expensive prints very closely. 34MP would be
pretty extreme for me, but 21MP means I have more data to work with
in the files and have less need to interpolate additional pixels.

Exactly.

We ("we" being the photographers) know to stand back at a reasonable distance and what to expect from a normal print. Someone who is about to pay $500 (or more) for a framed print in a gallery will put on their reading glasses and get to within 6 inches of it to "admire the details".

 

[Greg Henry]

Ok, so after reading the answers I see you now are aware that "around 19.4MP" is what you need according to your requirements for the specified size. You're looking for a reason to get a 5DMII, so now you have an excuse ;-)

However, please do not forget the LENS.

There is a lot of debate online right now as to just how much lens will be needed to get every bit of detail out of that 5DMII sensor. Some say the typical 24-105L lens will do fine - others say "no way". Some say only primes will be good enough - others disagree. Regardless, as with any camera, if the lens isn't good enough for all of those pixels, it's almost as if you're shooting with a lower resolution camera.

So when you get your new camera, make sure the lens matches, or your poster prints won't be as good as they COULD be (though no doubt they'll still turn out fine due to the res).

 

[Dragos Nenciu]

actually I tried both 300 and 240 and I can't see any diff.

Depends on the image content, obviously, but if you have adequate
detail in the image or fine repetitive patterns, such as picket
fencing or rail tracks etc., then you certainly will.

There are, of course, some specific but synthetic test patterns that
make the difference very obvious, but you are unlikely to see as
significant a difference with real world images - they simply serve
to determine the optimum settings.
--
Its RKM

--

I will have to do more tests most of my friends that use epson swear that 240 is better than 300 so they might be right. Personally I don't really notice the diff but like you say might depend on the subject.

 

[Dragos Nenciu]

Ok, so after reading the answers I see you now are aware that "around
19.4MP" is what you need according to your requirements for the
specified size. You're looking for a reason to get a 5DMII, so now
you have an excuse ;-)

However, please do not forget the LENS.

There is a lot of debate online right now as to just how much lens
will be needed to get every bit of detail out of that 5DMII sensor.
Some say the typical 24-105L lens will do fine - others say "no way".
Some say only primes will be good enough - others disagree.
Regardless, as with any camera, if the lens isn't good enough for all
of those pixels, it's almost as if you're shooting with a lower
resolution camera.

So when you get your new camera, make sure the lens matches, or your
poster prints won't be as good as they COULD be (though no doubt
they'll still turn out fine due to the res).

--

There are a lot of threads discussing 24-105 vs 24-70 on the 1dsmk3 and most people say that 24-105 is worse than 24-70 and both fall short on the 1dsmk3.

Some of those people say that the 24-70 is sharp on the 1dsmk2 (16.7mpx) but softer on the 1dsmk3 (21mpx).

Good telephoto zooms like 70-200 f2.8/f4 IS/Non IS should do fine.

Most L primes should do fine especially the telephoto ones.

I don't think the wide zooms, or mid range zooms are good enough at 21mpx especially wide open.

 

[Tangster]

Maybe the best way to answer you question is how many pixels can you afford? I mean if the budget is not there for a 5D II, A900, 1DsIII, or other MF cameras, it is moot to suggest a resolution.

Go for the highest resolution you budget allows.

--
Tangster

Rebel XT, 50D, 18-55, 28-135, 100/2.8, 17-55, 70-200/2.8IS, 50/1.4, 420EX, 580EXII, BG-E2N

 

[Dragos Nenciu]

Maybe the best way to answer you question is how many pixels can you
afford? I mean if the budget is not there for a 5D II, A900, 1DsIII,
or other MF cameras, it is moot to suggest a resolution.

Go for the highest resolution you budget allows.

--
Tangster
Rebel XT, 50D, 18-55, 28-135, 100/2.8, 17-55, 70-200/2.8IS, 50/1.4,
420EX, 580EXII, BG-E2N

--

A high res sensor with a mediocre lens will give worse results than a lower res body with a good lens.

So don't look at the camera resolution only. A 21mpx 5dmk2 will out resolve your 28-135 lens.

So you will get worse results from cropping the 21mpx image to 1.6x than you would get from your 20D with the same lens especially if you don't crop dead center.

 

[Tangster]

Maybe the best way to answer you question is how many pixels can you
afford? I mean if the budget is not there for a 5D II, A900, 1DsIII,
or other MF cameras, it is moot to suggest a resolution.

Go for the highest resolution you budget allows.

--
Tangster
Rebel XT, 50D, 18-55, 28-135, 100/2.8, 17-55, 70-200/2.8IS, 50/1.4,
420EX, 580EXII, BG-E2N

--
A high res sensor with a mediocre lens will give worse results than a
lower res body with a good lens.

So don't look at the camera resolution only. A 21mpx 5dmk2 will out
resolve your 28-135 lens.

So you will get worse results from cropping the 21mpx image to 1.6x
than you would get from your 20D with the same lens especially if you
don't crop dead center.

I do agree with your comment but the OP's question is how many pixel is needed which deals with sensors and body. After that, the OP will need to post again to figure out what lenses to use/buy to maximize IQ for that body/sensor combo.

--
Tangster

Rebel XT, 50D, 18-55, 28-135, 100/2.8, 17-55, 70-200/2.8IS, 50/1.4, 420EX, 580EXII, BG-E2N