Question on Resolution

[lorange]

Hello all,

I'm new to the forum, so please, go easy on me...

Anyway, I shoot with a Canon 30D. I'm still learning all about digital (and quite slowly, as it took me awhile to climb on board). I took some headshots and when I brought them in to get printed, the guy told me they weren't high enough resolution to keep good print quality at an 8X10. They would only look good at 4X6. I had the image quality set at Large on my camera, but I notice when I put it into PS, the image size is still 72 dpi.

I know that I'm probably getting things really mixed up (I know dpi is purely a printing measurement). But what do I set my camera at in order to get high-resolution prints without having to manually change the dpi in PS? Can I even do that without ruining the image?

AHHH! I'm confused... Any help would be appreciated. Thanks, all.

[mn shutterbug]

Your photos will always be 72 dpi, no matter the resolution set. A decent print service will resize them to 200 dpi for printing. With your 30D set at large resolution, and if you didn't do any cropping, you should be able to print a decent print up to 20 X 30.

Also, you can change the dpi in post processing without degrading the photo, but you shouldn't have to.

[Rocket_Scientist]

Your photos will always be 72 dpi, no matter the resolution set.

What does that mean? Is it specific to the 30D? My photos from the S3 IS (a P&S, not a dSLR) come out 180 dpi, or at least that's what they say they are. Am I missing something?

[mn shutterbug]

Gee Scientist, I don't know what to say. I just went in and opened a couple of my photos, 1 from my 30D and 1 from my Panasonic P & S, and they are both 72 dpi. Now you have me confused. I just know that mine, even the 9 meg. tiffs, are 72 dpi.

[mwfanelli2]

Gee Scientist, I don't know what to say. I just went in and opened a couple of my photos, 1 from my 30D and 1 from my Panasonic P & S, and they are both 72 dpi. Now you have me confused. I just know that mine, even the 9 meg. tiffs, are 72 dpi.

Look, the "dpi" of 72 or anything else is totally useless. Your camera records pixels, not dpi. You always get the same number of pixels at the same setting. Higher pixel counts, such as 8 MP instead of 6 MP give you more pixelss. The "dpi" value is useless to you unless you choose to use your own printer.

Any decent printing shop will set the equipment to distribute the pixels in the best possible way for the device. The print shop you went to is manned by a complete idiot. Go somewhere else and they should do it right.

[mn shutterbug]

Any decent printing shop will set the equipment to distribute the pixels in the best possible way for the device. The print shop you went to is manned by a complete idiot. Go somewhere else and they should do it right.

Bluntly put, but true.

[readingr]

Now Now folks, PS is set up to open at camera default. There is a setting which sets it to 300, 350, or any other number you want as a default. I think its under preferences but don't quote me.

Mine is set to 300dpi as a default regardless of the camera setting

Roger

[Medley]

Michael is on the right track. I never really understood print resolution until I spent some time trying to discover how best to sharpen an image for print. Here's some highlights from my findings:

All printers have a "native resolution". This is the resolution that the printer itself will size an image to in the process of printing. As most of us are already aware, sharpening an image increases the contrast at it's edges. In so doing, it creates a "halo" of a certain width an intensity.

Now, if a printer downsizes an image to get it to its native resolution, then the width of the sharpening halos are also downsized, reducing the effectivness of sharpening in the final print. Conversely, if the printer has to upsize the image dimensions, then the width of the sharpening halos is increased as well, resulting in more sharpening than was intended. A printer's native resolution, then, is defined as that resolution where the sharpening halos are passed through to the final print without increasing or decreasing their size.

As it turns out, the native resolution of most printers is at or about 300 dpi. The native resolution of Epson printers however, is much closer to 360 dpi. Commercial or home, it really makes no difference. The native resolution is what it is.

So if I want my Canon printer to print an 8x10, I know that the printer is going to require pixel dimensions of 2400x3000. By resizing the image to those dimensions before I sharpen, I ensure that my sharpening halos won't be resized. Creating sharpening halos that are exactly 3 pixels wide will produce halos that are 1/100 of an inch wide- every time.

The only way to get my Canon to print below its native resolution is to send less information to the printer. If I want to print an 11x14 at 200 dpi, I send an image that has dimensions of 2200x2800 pixels. The printer is still going to upsize it to 3300x4200 pixels (300 dpi), and increase the sharpening halos accordingly. But knowing this in advance allows me to adjust the width of my halos to get the desired outcome.

When printing an image at anything less than its native resolution, it is best to keep the resolution an even multiple, as the printer will do a better job of upsizing the image. For printers with a native resolution of 300 dpi, a resolution of 150 is good, 200 is better, and 300 is best. For an Epson, those numbers are 180, 240, and 360 respectively.

Lastly, I apologize for starting a discussion of sharpening. My intent is not to take the thread off-topic, it's just the only way I know to discuss native resolution.

- Joe U.

[lorange]

No apologies-- I'll take all the information I can get! Thanks!

[Rocket_Scientist]

Well, I do print my own--when I use prints--and the "native" resolution(s) of my little HP is (are) 300, 600, and 1200x600. I usually do not worry about reconciling the pixels with the printer, but that's a good idea. However, when I crop or resize in PS (or Elements) it does use the "dpi" information in its calculation(s). I wonder how much this depends on the screen resolution... I have found that when displaying photos on a web site, it is often better to resize them to 96 dpi, using reasonable pixel dimensions.

[Medley]

R.S., don't confuse your printers' maximum resolution with the resolution it normally prints at. If you make two prints, one at 300 dpi and one at 600 dpi, I think you'll find that the 300 dpi print will look sharper in the end, because the 600 dpi print reduced the sharpening halos somewhere along the line.

- Joe U.

[gahspidy]

My concern is that you did something to the files before bringing them in to print. any decent print shop would have been able to bring a high quality file from that camera to a format to print a decent size and quality photo. Did you load the shots into your computer first and then adjust them somehow? It could be that in doing so you mistakenly resized them what would be ideal for web display but inadequate for print.
Fill us in on more details . . .

[Cate]

Hi guys I'm new to this, I have a casio digital camera 10.1 megapixels it only shoots at a resolution of 72 mega pixels the pictures are not of the quality I would like as I'm an artist. Anyway if there is some way I can change this please let me know. Kind regards Cate

[fx101]

All you should really care about is that the final image, when resized to 8x10, will print at >200dpi (c-tone dpi count: I'll explain what this means later). How do figure out the dpi given camera resolution and desired print size? (Horizontal-pixels/)x=desired-horizontal length where "x" is the dpi. So, for example, your camera's image size is 3504 x 2336. You can use the formula with either vertical or horizontal but we'll chose horizontal. 3504/x=10 (for an 8x10). x=1752/5=350.4dpi which is more than enough for any kind of printing. Just for reference, professional LED or Laser based exposure c-tone printers use a maximum of 300dpi (with one exception). Now what the guy doesn't understand is that an inkjet is NOT a continous tone device (c-tone) (that is, the image is composed of scattered dots of cyan, magenta, yellow, and black to represent one pixel of your image instead of one pixel of the exact colour ink for every pixel of the image) so these inkjet printers work at higher dpi counts than what most cameras can produce. They are printing 1200 or so dots of ink per inch; however, the printer is printing multi-coloured dots (half-toning as it's called) on the paper for every pixel so it will need more dots than what is contained in your image, spaced closer together, to allow your eyes to blend them together to see the image correctly than a device such as a lightjet that exposes one dot of the exact colour for every pixel of your image. That being said, they should have the equipment to resize images quite readily available. You shouldn't need any fancy enlargening software (like genuine fractals) since you are printing on small media and your scaled image dpi was 350.4 as I previously stated. All you care is that using the method I showed you you get >200 dpi so that your images are crisp when printed. You have no reason to resize in photoshop. The printer should do this automatically. I would try a different shop if I were you.

Hi guys I'm new to this, I have a casio digital camera 10.1 megapixels it only shoots at a resolution of 72 mega pixels the pictures are not of the quality I would like as I'm an artist. Anyway if there is some way I can change this please let me know. Kind regards Cate

The "resolution" cannot be 72 megapixels... do you mean dpi? Of course it shoots 72dpi. This is what it's supposed to do. 72dpi is the number of dots per inch on your screen. If you want to send for your images to be printed at a professional lab then you simply resize the image in photoshop to 300dpi (or whatever the lab requires) and you end up with the exact same image with same dimensions only that the PHYSICAL printed dimensions will get smaller. You're increasing the printed resolution of your image at the expense of the printed size of your image.