dpi...?? (1 Viewer)

You say the dpi is irrelevant and labs will automatically set the dpi but if you read the likes of Proam's requirements that isn't the case and in their forum it clearly states that files supplied incorrectly will be printed wrong. Fair enough you don't need to use a lab like that but they are a quality lab and so I just think that the thinking behind your posts and the article you linked to could trip people up.
To specify 402dpi and 400 for Jorgenson albums all sound very specific to me.

I do totally agree that some thought needs to go into how a file is prepared for printing and knowing when to resample and when not to but it ain't rocket science

paul goode said:

Well , I've read that Roy and it all makes perfect sense.
Trouble is it wouldn't help if your lab was Proam or Peak Imaging who strictly specify the format files must be submitted in. Do we take it from the arrogant tones of your post and the article you linked you that these labs are populated by bone idle lay abouts who merely want an easy life or is there more to it.

Click to expand...

Paul I am sorry if you find my tones arrogant but I have great difficulty in putting my thoughts in to words.
As I see it the original poster was under the impression that changing the dpi would somehow give him a more detailed image. My original response was to try and tell him that it is a printing function and not related image quality - I reckon a good way to emphasize this was to state that the file size does not change no matter what the dpi is.
As you will see, the first response to my post was to challenge this and state that changing the dpi does indeed change the file size. which is clearly not the case.

I posted the link as I thought it would be a good read for someone who does not really understand all this stuff - it is obviously basic stuff to the likes of you so was even suprised that you bothered to read it, but do you not think it could be helpful for someone like Westley?

I may be wrong but I do not think is original post had anything whatsoever to do with printing and after all the subsequent post his head must have been in a spin which is why I tried to simplify things for him in post# 18.

I should have know that every word I wrote would be scrutinised and that brownie points would be scored but I guess that is all part of the game LOL

BTW I do not doubt for a minute that some of the labs you use ask for the dpi to be included in the file but am still at a lost as to why - there probably is some logical reason but I am darned if I can think of one.

I guess arrogant was a bit OTT but your comment
"What I find unbelievable is that some print shops still ask that clients send their shots at xxx DPI (usually 300 dpi) instead of asking for what they really want,"
did sound as if you know more about digital printing than 2 of the labs I use

If thats the case I humbly apologise

Both state that the dpi they require is the native resolution of the printers they use. Assuming this is correct then the pixel dimensions need to be bang on for the image to print correctly.

and I do apologise to the OP for hauling the thread miles off course. But then this is a Birdforum thread

well this is all over my head by a long shot..|8.|

yes my original question was if it makes a difference to image quality, i now get that it doesnt make a difference to digital quality but it does to print quality,

if and when i get prints done then i'll be using a print shop so hopefully i can just give them standard files and they can do whatever they have to do to make it right..

i have a 450d and shoot in 12mp fine, it is the top setting apart from RAW, so would this setting provide the best image quality? as i dont want to shoot RAW as i havent a clue how to convert them.

i also use photoshop elements 7, i also dont have a clue how to use this either, is there an 'idiots' editing software i could get so i can teach myself from the basics up or is ps elements 7 the most basic one??

cheers
wes

wes,
using jpeg fine will produce fine quality images until you are ready for raw (the sooner the better I suggest )

elements 7 is a good package which will allow you to develop your editing skills quite extensively
I had a look on amazon and saw this

http://www.amazon.co.uk/Photoshop-E...=sr_1_2?ie=UTF8&s=books&qid=1270318869&sr=1-2

the reviews are a bit mixed but I'd have thought it will give a good grounding in elements 7 and its only a tenner.

lovely cheers mate, will have a look

Wes,

Roy's right here.

But you have to be careful, on resolution size, your sensor gives you the maximum resolution available, but it's the lens on the camera and how close you are that will determine your enlargement factor against the number of pixels from which you can enlarge your image.

Different output resolutions will vary the size you can enlarge to.

The golden rule is to remember only enlarge to a 100% of output resolution.

With a D3 you can push the figure a bit, but go beyond and the image will deteriorate, it will look soft and flat when reproduced at high quality.

With the web you can get away with murder. So don't panic about having to know the fine details on resolution.

In theory the more Mb's a camera has the better the enlargement factor, stick a 600mm on the camera and your image covers a larger population of pixels.

But if your up close to your subject with a 50mm again you are covering a wide population of pixels.

DPI vs Print Size Quality

The way I try to explain these relationships, and it can get confusing, is to think of an image having a finite number of pixels in it.

Let's say the native image out of the camera is 900px high x 1200px wide at a dpi of 300.

That means that there is 300 dots of ink per linear inch, giving a print size of 3" x 4" (900/300=3, 1200/300=4).

Let's say in PS under Image Size, ensuring the "resample" box is unchecked, you change the value in the dpi box to 100 dpi. What essentially happens is that PS is being told to spread out the pixels in the image, so that there is now only a 100 dots of ink per linear inch. So the print size is now 9" x 12" at 100 dpi.
900px/100dpi=9", 1200/100dpi=12"). There is still the same number of pixels within the image, they have just been spread around. Thus the image at 3"x 4" at 300 dpi and the 9"x12" at 100 dpi are exactly the same file size.

The issue comes in when you check the resample box. That tells photoshop to either add or discard pixels independent of the dpi.
I like to think of the resample box as the "adding or throwing pixels away" box.

Example - take our original 900 x 1200 pixels image at 300dpi at 3" x 4".
If a magazine wanted you to send this as a 6" x 8" image at 300dpi, you don't have enough pixels in the file. Changing the size in PS in the Image size dialog box would result in a lower dpi since the pixels need to spread over twice the area. This results in a size of 6" x 8" at a dpi of 150dpi.

Since that is below what is needed for a nice magazine print (300dpi), then you would check the resample box, and change the dpi from 150 to 300dpi. You will see that the size and dpi are now independent of each other and that by checking the resample box, you are essentially telling Photoshop to make a guess and add in the extra pixels needed. This is known as interpolating up, or rezzing up.

The opposite, when asked for a file that is smaller than the native size results in a dpi higher than 300, you do the same resampling to discard the extra information and reduce the file size.

So, dpi and pixels vs print size can be confusing depending on what the output is. Hope this helps and isn't at all patronizing?

best,

julian

cheers julian, thats made it much more easier to understand..
'just now need to learn how to use photoshop' going to get someone local to show me the basics i think as reading up on it isnt as easy as it seems..

wes