Newb to Digital - would I notice 2X the camera megapixels?

[Gizmo]

Hello all,

Long time photographer here but relatively new to digital. I currently have a Panasonic DMZ-FZ7 (6MP) and want to do mostly B&W for framing in the 8x10 to 11x16 sizes. I would probably use an outside printer for actual prints.

I am considering a new camera...specifically the DMC-G1. (I like Panas). My question is this...

Would I see a great difference in resolution/sharpness in those print sizes going from a 6MP to a 12MP camera? I have been reading the tutorials and other references but I just can't seem to get my head around the whole print size/resolution/image sensor size relationship.

One reference says to take pics at the highest resolution possible and another says I don't need higher resolution for my intended print sizes.

Any advice?

[Colin Southern]

Hi Gizmo,

Here begins a journey

If a printed image of a given size has a relatively low number of pixels then if you keep reducing the viewing distance there will be a point where you will realise that your eyes are capable of resolving more detail than is actually present in the image, and it will look "pixelated".

From this people may deduce that "the more detail that the image has, the better" ... while this may be true in theory, there is also very much a practical upper limit - beyond which you rapidly get into the "law of diminishing returns" category where you'll be unable to see any benefit in having more information FOR A GIVEN VIEWING DISTANCE.

Viewing distance is the key to all this - and in this regard, the world can be divided into two groups: (1) "Normal People" and (2) "Photographers". Normal people stand back and look at an entire image at once; the bigger the image, the further they stand back (and this the less detail their eyes can resolve) - so in this regard you tend to find that for shots over 8MP you can basically print "as big as you like" if it's to be only viewed by "type 1" people. Type 2 people (photographers) unfortunately, are a different breed - we tend to view images at 100% magnification (or greater) and our minimum viewing distances are limited only by the length of our noses (although personally I also have a magnifying glass!).

So often you'll hear photographers say things like "you can get by with as low as 360dpi, but 720dpi will look better" (insert "rolls eyes" here!).

... a quick primer on print resolutions ... a "very modest" print resolution of, say, 175dpi is the same as 7 pixels per millimeter (roughly 25 millimeters in an inch) ... but because we're dealing with print AREAS we need to square this to get the figure in "per square millimeter"; 7 squared is 49 ... lets call it 50. If you had an image printed at 180dpi then that would equate to up to FIFTY tone changes in each and every square millimeter. Could your eyes resolve that? At any distance? Mine sure can't. At 360dpi you're talking about 200 tone changes in a single square millimeter. at 720dpi you're talking about over EIGHT HUNDRED tone changes in each and every one single square millimeter of print. So the point is, most photographers go way waaay waaaaaaaaay overboard when it comes to print resolutions. Personally I work with 44 inch by 22 inch canvas prints at 180dpi and they look just fine ... I even go down to about 100dpi and they still look fine.

So (finally) to look at your questions ...

The Panasonic DMZ-F27 has pixel dimensions of 2816 x 2112 which equates to a print resolution of 176dpi for a 16 x 11 print. The Panasonic DMC-G1 has pixel dimension of 4000 x 3000 which equates to a print resolution of 250dpi for a 16 x 12 inch print (side note: sensor size doesn't enter into it - it makes a difference with regards to apparent changes in focal length, but doesn't affect print resolution). In the "real world" 250dpi -v- 176dpi won't be noticeably different; you MAY be able to see a small improvement when viewed under a microscope however.

For what it's worth, I have 44" canvas prints hanging on my wall from 8MP cameras and 21MP cameras, and even other professional photographers agree that they can't really see any difference (to the point where they'd be uncomfortable trying to work out which print came from which camera).

Hope this helps!

[PopsPhotos]

I've found that I can take 6Mp shots up to 16x20 with no problem at all. The shot I have of the Frozen Fog is a 1/3 crop of the master, and it was resampled at 300 by PhotoShop7 to get it up to 16x20. It looks just fine when viewed at a yard or more distance. The fine points of the ice crystals was retained and most people never notice the grain and such.

When viewing a print, step back until your eyes can take in the whole picture without having to change your direct focus point. That is the point where most people viewing it on a display with look at it. When somebody steps up to the print and looks at it from a step or less away, you have spotted a photographer. Painters know this without thinking about it. You will see a painter step back from his work as he is working to see what needs to be added, detracted or changed.

Pops

[will_c]

This is from an earlier discussion of this issue:

The closest comfortable viewing distance for a print is about equal to its diagonal, I believe. Held normally at that distance it subtends a little under 50 degrees horizontally at the eye. Someone with good vision has an angular resolution of about 1 arc minute (any details separated by less than that are indistinguishable). Allowing one pixel per arc minute and the usual 3:2 width to height ratio, that makes a bit less than 6 MP in total.

So there is a good basis for believing that there are rapidly diminishing returns above about 6MP. I still see no reason to think that this is wrong. So, whatever your print size, if it is to be viewed in a normal way by normal people (not by pixel-peekers or peregrine falcons), good quality 6MP in the output will almost certainly be enough. I suppose that to be really thorough with a given camera you would need to look at the effectiveness of the processing (demosaicing and so on), but I still suspect that the megapixel race has been focused for a long time on people who take photographs, not on those who view them.

[Gizmo]

Thanks very much for the replies. I think I'm catching on with this resolution thing. As I understand it, for my specific purposes, my 6MP camera should be fine considering it has more resolution than any printing method out there as long as the pics do not get enlarged too much (beyond 11x16 or so). Is this true?

On another note, how does image sensor size relate to sharpness and clarity in a print? My camera has a 1/2.5 sensor, very small indeed, as DSLRs and micro 4/3 camera seem to produce better looking photos due to thier increased sensor size and pixel density. And these cameras seem to be used by many semi-pro and pro-am photographers, and none seems to use UZ compacts like mine.

And one more thing if it is not too much trouble, are "pixels" on a sensor all the same size? When tutorials and such talk about pictures made up of pixels, they don't seem to mention the size of the pixel. Is there a standard size? If pixels vary in size, that seems to throw a monkey wrench into the whole resolution machine.

Thanks again for your support.

[Dave Humphries]

Hi Gizmo,

Have a read of these, they explain better than I can

Understanding Digital Pixels: PPI, Dithering and Print Size

Understanding Diffraction: Pixel Size, Aperture and Airy Disks
This one is a bit advanced, but it does have a table of pixel sizes in.

Digital Camera Sensor Sizes: How Do These Influence Photography?

Hope that's not too much of a 'fob you off' answer.

[Bill44]

The one time when more pixels helps is when you can't get close enough to fully frame your shot, then the crop you have to make will still have enough pixel density for a fine large print.

really helps me in sports action shots.

[Colin Southern]

Thanks very much for the replies. I think I'm catching on with this resolution thing. As I understand it, for my specific purposes, my 6MP camera should be fine considering it has more resolution than any printing method out there as long as the pics do not get enlarged too much (beyond 11x16 or so). Is this true?

Hi Gizmo,

The easy way to work your "max" print size is to simply divide the pixel dimensions of your sensor by whatever resolution you're happy to work with (I'd suggest 180 as a starting point). So if the camera has 3000 x 2000 pixels then your "max" print size would be 3000 / 180 = 16.67" and 2000 / 180 = 11.11 inches.

On another note, how does image sensor size relate to sharpness and clarity in a print?

On a basic level, it doesn't - but - on a more advanced level the smaller the sensor the greater the depth of field, and, the more noise the shot is likely to have (because of the reduced light gathering ability of the sensor) (whether or not the noise is an issue though will depend on other factors). And a phenomenon called 'diffraction" also comes into play, which again, may or may not be an issue in reality.

And one more thing if it is not too much trouble, are "pixels" on a sensor all the same size? When tutorials and such talk about pictures made up of pixels, they don't seem to mention the size of the pixel. Is there a standard size? If pixels vary in size, that seems to throw a monkey wrench into the whole resolution machine.

They're all the same size on any given sensor, but different sized sensors will have different sized pixels, and thus different pixel densities.

In a nutshell, you probably don't need to be concerned with pixel densities - they're really only useful when working out the effective focal length of a camera/lens combination when compared to another camera/lens combination. (don't ask! )

[Prof. Jewell]

Short reply: at a 2X increase one will only see a difference if two same sized photos of exactly the same scene, but with the different sensors, are placed side by side. It would probably take a 4X increase (think about the make up of a Bayer sensor) to have one J N D between the two prints hanging in separate rooms.

Two reasons. The first has been known 'forever' in wet photography, in spite of

Someone with good vision has an angular resolution of about 1 arc minute (any details separated by less than that are indistinguishable).

It is true that the unaided human eye cannot resolve more than 5 to 7 lines per millimeter, but it is also true that the untrained human eye still 'detects' with high accuracy, the difference in a print which only resolves 7 lines per millimeter compared to one which resolves 15 lines per millimeter.

The second reason I stumbled upon more decades ago then I would like to admit. I teaching aesthetics and became curious as to the effect that captions under a picture would have on what was perceived 'in' the picture. Placed pics on the wall of my office--paintings, photographs, graphics, prints, etc., with captions under them, then if visitors voluntered to discuss any of them, after they left I would take careful notes as to what they said in connection with one or all of them. Every month or so I would change captions and was hoping that after nine months I would gain some knowledge about the role of captions. About four months into the project I started to gradually become aware of something quite different from the caption effect.

When somebody steps up to the print and looks at it from a step or less away, you have spotted a photographer.

One of the items on the wall was a 20" x24" photograph printed on "N" surface paper (not a hint of photo glossiness) of a covered bridge crossing a stream in a valley in southern Appalachia. Up on the side of the valley beyond the bridge was a small shed with an animal beside it. On the print the shed was no more that 1/4" wide with the animal no more than 1/16". I had included the shed in the picture as "local color," but I not sure I had noticed the animal even during printing. Yet it began to be apparent both to my eyes and in my notes that as soon the viewers identified the picture as a photograph--not a painting or a hand drawn print--they would move closer to see if the animal was a horse or a cow. They would never do this with similar passages in the paintings or other hand work.

If it's a photograph, the 'diagional distance' rule is thrown out the window. {It's surprising what one learns, if one actually observes!} Which, if one thinks about it, is a corollary of the old standard for a photographic print, namely, an 8" x 10" contact print.

[will_c]

If it's a photograph, the 'diagional distance' rule is thrown out the window. {It's surprising what one learns, if one actually observes!} Which, if one thinks about it, is a corollary of the old standard for a photographic print, namely, an 8" x 10" contact print.

This is interesting, but can you even focus comfortably at a distance that is less than the diagonal of an 8"x10" print? Most adults can't. Even for 11"x16" most adults can't get a lot closer than the diagonal without some straining. One does not often observe people with their noses up close to a print in a magazine, for example, because it's uncomfortable (and pointless). A 20"x24" print could be viewed differently because you can potentially focus closer relative to its size (not absolutely closer of course), but the original poster is not talking about making these. For smaller prints the diagonal is probably still a reasonable rule of thumb and then you do not gain all that much from increasing the horizontal and vertical resolution over 6MP (again, subject to those 6MP being reasonably well reflected in the output).

[Colin Southern]

My observation is that people like me slave over every pixel at 100% magnification - but when I run the printed image past the quality assurance department (usually the kids), the whole proces takes about a second, and goes something like this:

"Cool photo Dad - where are we going for tea"!

[Gizmo]

Well, that is a lot of info, thanks everyone. My photos look pretty decent on the comp screen and I have had a couple printed in 8x10 fromat at an online printer that came out wonderful. On close inspection though, some details are lost and I think a higher resolution camera may remedy this.

I do have one more question though. When I open up my photos in Photoshop Elements, when I go to resize the photo, it says my original image is 39.xxx inches wide. Where does it get that arbitrary number? When I view it at 100% it is huge and the photo looks crappy but I usually crop and resize to about 10" wide. (I do not conform to standard frame sizes, I just crop to make the photo look good with future mounting a possibility, in other words all my photos are weird sizes, but I keep them under 11x16 for sharpness reasons).

I'm just curious about the default image size, 39.xxx seems kinda arbitrary. Is there math involved?

[Colin Southern]

I'm just curious about the default image size, 39.xxx seems kinda arbitrary. Is there math involved?

The software assigns a default DPI - probably 72. So if you divide your pixel dimensions by the DPI you get the size it would print at. Until you actually print it it's pretty much meaningless (in affects font sizes, but that's about all).

[Gizmo]

So when i resize my images, should I change that 72dpi to something else? What does that number mean? Is it the printing resolution or what?

Sorry for all the ???. I'm kinda lost on the resolution between image sensor, Photoshop, and print resolution.

I'm Confuzzled.

[Colin Southern]

So when i resize my images, should I change that 72dpi to something else? What does that number mean? Is it the printing resolution or what?

Sorry for all the ???. I'm kinda lost on the resolution between image sensor, Photoshop, and print resolution.

I'm Confuzzled.

If you're only displaying them on a screen then it doesn't make any difference what it's set to -- it has zero bearing on the quality of the image. If you're always printing at the same size - and you don't crop - then the figure can be changed so that you don't need to resize the image for printing (in theory) but in practice it's easier just to resize.

A lot of people seem to struggle with this - but it's really pretty easy; your camera captures "X" number of pixels across and "Y" number of pixels down ... divide that by the number of pixels per inch and that's how many inches wide and high a print would be. eg if your camera captures 3000 x 2000 pixels and your print dpi is 100 then the print will be 30 x 20 inches. In reality though, you set the print dimensions (eg 12 x 8) and the dpi is whatever it is (eg 250dpi).