dpi question

JumboBeef

JumboBeef

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Hello,

I have had a client ask for a TIFF file at at least 300dpi at 452 mm wide.....

How can I check my TIFFs are within this spec please?

Thanks.
 
DPI is dots per inch and it should tell you on the exif information
 
Probably wants them for printing, looks rather large as well. Does he state if this dimension is the longest one?

To find out simply go into Photoshop. Image> Image size. This will tell you the dpi and the image size. That's going to be a big file 50+Mb
 
If his image is only 150 dpi, in photoshop you can tell it to increase the DPi to whatever you like, this does create a bigger file but does it damage the quality?
 
assuming that's the long edge then the min pixel dimensions would be 135,600 x 90,400 (3:2 ratio) which is about 12 MP.
 
I would ask what screen he's going to use for printing (measure in lpi). A 250dpi image would be fine for a 150lpi screen.
 
His client wants 300dpi at 452mm wide or greater, so he needs to resize the image to 300dpi, width 452mm or greater and then save it, give the client what they want.
 
Steep, does increasing DPi in PS reduce quality?
 
Chappers said:
Probably wants them for printing, looks rather large as well. Does he state if this dimension is the longest one?

To find out simply go into Photoshop. Image> Image size. This will tell you the dpi and the image size. That's going to be a big file 50+Mb
Click to expand...

It's for a glossy magazine.

I can only find PPI in my PSE6. At 452mm, it gives me 240PPI. How does PPI relate to DPI?

Thanks!
 
Google tells me:

if you want to know how many PPI you need to get 100 DPI, its pretty simple; take the number the printer give you and multiply it by 2 (if you are a paranoi kind of guy) or 1.5 is way OK. So he need 100 x 2 = 200 PPI. The reverse is simple to, assuming that when people ask you for a 300 PPI file, that should mean they print at around (300 /2) 133 or 150.
Click to expand...

So does this mean my 240PPI will only give me 120DPI? That is well short of the spec my client wants.............
 
OK, so I've worked out I can resample the file, to take it up to 300ppi, but do I need to take it up to 300PPI, to be more than 300DPI.....?

When I resample, should I use bicubic, bicubic smoother, bicubic sharper, bilinear or nearest neigbour?
 
I can only tell you how to do it on my sofftware which lets me state the physical size of the image and the dpi in it but to clarify the difference between dpi and ppi...

DPI is specific to printing and refers to the number of actual dots that the printer can print in one inch of paper. (nicked off the net >>--> Generally, the higher the DPI, the better the tonality of the image, colours should look better and blends between colours should be smoother.)

PPI relates to the size of the image (also nicked >>--> To calculate a photo’s PPI simply multiply the page length by its width in inches. The result is the number of square inches on the page. Now divide the number of pixels the sensor supports by the number of square inches. The result is the number of pixels per square inch. All that is left to do is to find the square root of this number.)
 
Its my understanding that 300 dpi is the minimum printing industry standard, (For any size image)
Its needed to be this way because mechanical mass printing presses need to place the different coloured dots on top of each other and in exactly the same place so as to maintain truly accurate colours.
These machines are designed in general to use an accuracy of 300dpi upwards, nothing less than that is accurate enough.
Each colour is applied as a separate printing pass so any inaccuracy will mean dots will be blurred .... eg a red dot covered exactly with a yellow dot makes orange.... if the dots not placed directly on the top then you'd get a slightly different, wrong orange.


Something like that. :thumbs:
 
300dpi is used because it looks sharp at reading distances
 
One last question: still talking about PPI etc, would the 450D give a 'better' picture than a 40D?

Thanks.
 
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