P&S File Size is 72 dpi normal?

[john_n._wall]

I just got my first digital camera after lots of experience scanning 35 mm film.

Having made some test shots, I opened my first images in Photoshop and was

surprised to see that my files opened at 72 dpi.

 

I am accustomed to printing (from scans of film) at 300 dpi, regardless of the

size print I want to make. I'm accustomed to thinking of files at 72 dpi as

being low resolution and appropriate only for use on the Web.

 

Is it customary to have files come from a digital camera at 72 dpi? How does one

get from a file at 72 dpi to one at 200 or 300 for printing?

[leopoldstotch]

DPI has nothing to do with the file itself or the camera. The 72DPI you mention is what the software you are using is set to print at. To make is 300DPI, change the printer settings in whatever program you are using. DPI is only used as a printing resolution, not resolution from a digital file.

[john_n._wall]

OK, I'm not talking about a number I get in the Print routine, but number I get under "Image>file size" in Photoshop. I'm accustomed to opening scanned files in Photoshop at this point and they open at 4000 dpi.

I gather from your comments that I can increase the dpi size to 300 from 72 simply by changing to that number at Image>file size. I will try that.

[Spearhead]

The dpi setting is header information to an output device. It can be set to anything until you pump it into a driver or print output application. Most scanner software just uses whatever the scanning resolution is, but that too is irrelevant once something is scanned, since all you have is file with dimensions, not anything related to inches.

[ronald_moravec1]

PPI, not DPI, is a camera setting to detirmine the quality of the image.

The photographer sets it in the camera by selecting a large file size if no other way is provided.

 

The Canon A series get 180 ppi max. I have used 3 of them.

 

That is all you get from a small sensor 1/4 in square.

 

An APS C will be 300 ppi native.

 

Pumping it up to a larger number will reduce the print size as you can`t make something from nothing.

[craig_gillette]

It's a data tag that's meaningless. Don't worry about it. A historical relic from the development of the spec for a JPEG file.

 

Not all cameras save at 72 dpi. Some save at 300 dpi (per the tag). Print drivers take the pixels you have and place in the space you tell them you want the picture to be sized to. Monitors place your pixels in a nice array across the screen, one after another, one above another. If you have a 3000x2000 pixel image, whether it "says" 72 dpi or 300 dpi, if you set your screen to 1024x768 (for example), you get about 1/6 of the image on the screen and the rest off - so you scroll. If you've resized it to 1000x667, then the whole image shows.

[Spearhead]

Ronald is wrong. The setting is arbitrary. There are no inches to the file cranked out by a digital camera, so dpi and ppi are meaningless. They can be changed to whatever you want and won't affect anything until you print. It has nothing to do with the size of the sensor.

[kelly_flanigan1]

The intent of the "72dpi" tag was for new folks. It was purposely placed in the header; since many older programs and folks use the 72 number; which is older than Photoshop; it does back into the DOS era. Think of it more like a serving size on a can of beans; average shoe size, average unit of coca cola sold, average size of a ball of yarn or roll of duct tape. If one wants 5000 ft of wire for some house wiring; one can buy twenty 250 ft spools or ten 500 ft spools. What matters is the number of total feet of wire. The 72 number seems to bother folks new to digital photography for some reason. Worrying about this number is goofy. The 72 number is older than the jpeg spec; It once was the resolution of a decent high end monitor in pixels or dots per inch. Thus "thinking in 72" was so an image one is working on at 3x4 inches at 72dpi/ppi looks like a 3x4 inch image on ones 72 dpi monitor. Whats bizzare is how folks are baffled by something made to help the beginner. Its like buying 96 Large eggs for a scout trip and being baffled because one dozen is marked feeds Y servings; and another dozen is marked feeds X servings. One can argue all day on how many glasses of milk, cans of beer, number of eggs, rolls of film, megabytes, cellphone minutes, space food sticks, spiderman digital cameras an average person requires in a time period of a quad-ro-centon. Or argue than your monitor is setup differently than Britney's. <BR><BR>The number of pixel is what matters in an image. Worrying about the 72 number is like worrying about how a client is going to pay you 1/2 grand in cash. Most rational folks would take five 100's' or ten 50's; or twenty five 20's. The "72 worry warts" would not focus on the number of dollars; but worry deeply about maybe not accepting the anything but the common bill; the twenty. <BR><BR>Pixels are like dollars, gallons or water. If the gas pump was charged to firkins in Iowa; maybe a compact car #1 would get 1 firkin; pickup truck #2 2 firkins; inkjet cartridges would be in nanofirkins or picofirkins. <BR><BR>One can use a 100year old receipe that uses lbs of flour; number of large eggs, cups of milk, and aperosn can buy these items today in a store. An image thats scanned 2 decades ago in our engineering scanner thats 9600 by 14400 pixels is the same number today in pixels. This is a monochrome 24 x 36 inch 400 dpi group 4 tiff file' thats about 250k for a clean drawing; and about 1 meg for a rough dirty one. One of these 9600 by 14400 images often appears as one thats 400/72 larger in Illustrator; since many versions default to the 72 number; unless you change it. <BR><BR>If one wants to scan color artwork on our new 36" wide rgb scanner; one can use the 200 thru 600 dpi settings. Scanners do this because one is scanning a physical real map, drawing, or piece of artwork. If one sends an image to Jeff to print on a magazines glossy cover; a Brabie Cams 120x160 pixel images is way to poor; unlsss its a one of a kind image of bigfoot, a UFO etc. It really doesnt matter what image tag the 120x160 image has. <BR><BR>The "72 number" was added to an image files tag for a reason; to hopefully help begineers. Maybe it backfired, maybe its like servings per potato chip bag; or labeling the number of brushings per toothpaste tube; or bathroom vists per toilet paper roll? If bathroom vists per roll magically appeared on toilet paper rolls would folks be baffled; argue is too high or low? Rolls are really sold more by weight; the fluffed up rolls would have lower numbers. <BR><BR>Strive to communicate in pixels, dollars, lbs or kilograms of flour; units that mean something to the other person. A person in the USA midwest on a 1840 wagontrain can relate to the number of pounds of dried beans, gunpowder, flour, soap. The "72 number" without any way to figure out the actual number of pixels in an image is a hokey way to do business. Pixels, Lbs and Kilograms will be understood when we are all dead and gone 100 years from now. If the 1840 wagon train used lime Shrek glass cups for units; and they are all gone; the diary might not give the really number of beans used for a trip. <BR><BR>

[kelly_flanigan1]

With hotdogs the number of buns per package and number of dogs per package is not the same. One might start with a header tagged as 1 hotdog per person per Dodgers game as wild guess. Some folks will argue that hotdog is not the proper term; write a book; go on a crusasde with a new name. Others will argue that the 1 hotdog per person number is arbitrary; or used to cook the books of the club. The bun folks and dog folks might have union contracts; and find some non union buns are on the line. Hotdog.net's value as a web site might soar with the confusion over bun and dogs sales are not perfectly in line.

[jcuknz]

Kelly Flanagan's replies should be preserved for posterity and automatically sent to all new purchasers of digital cameras :-))

 

Basically forget about dpi until you come to make a print, what is important is the resolution/number of pixels you shoot with in the camera. Also that you have a programme that will interpolate to maintain the DPI when you print larger than what your native camera resolution provides.

[r_weistra]

I agree. Read my article:

Misunderstandings about dpi - www.dpiphoto.eu/dpi.htm