# Thread: how many pixel is good for a 4R printout?

1. ## how many pixel is good for a 4R printout?

hello people
my 9MP camera give me a 3488x2616 - 72dpi - image size

i want to reduce the file size as it is too big to be sent to alot of people and they just want to print them out in 4R.

What is the recommeded size for a good, sharp, 4R size photo?

with 72dpi.. what "??? x ???" should i put use?

thank u =)

2. ## Re: how many pixel is good for a 4R printout?

Originally Posted by Poopy
hello people
my 9MP camera give me a 3488x2616 - 72dpi - image size

i want to reduce the file size as it is too big to be sent to alot of people and they just want to print them out in 4R.

What is the recommeded size for a good, sharp, 4R size photo?

with 72dpi.. what "??? x ???" should i put use?

thank u =)
1728x1152 should be enough...not sure how to do the calculations so i simply took
6"x4"x72dpi=1728
1728 * (2/3) = 1152

3. ## Re: how many pixel is good for a 4R printout?

6"*72 x 4"*72 = 432 x 288 = 0.5MP

4. ## Re: how many pixel is good for a 4R printout?

Hi Poopy,

As a rule of thumb, you can use 300 dpi for hardcopy printing calculation. So for 4R size which is 6"x4", you need:

6" x 300 dpi = 1800 pixels
4" x 300 dpi = 1200 pixels

Hope that helps.

(Btw, 72 dpi is the screen density, which is not good enough for prints)

5. ## Re: how many pixel is good for a 4R printout?

Originally Posted by espn
6"*72 x 4"*72 = 432 x 288 = 0.5MP
Last time I sent in shots at 600x400 at 72dpi but turned out blur...

Anyway, the dpi don't really matter, what matters is the printer in question. => By my school instructor, a full-time pro

6. ## Re: how many pixel is good for a 4R printout?

Originally Posted by +evenstar
Last time I sent in shots at 600x400 at 72dpi but turned out blur...

Anyway, the dpi don't really matter, what matters is the printer in question. => By my school instructor, a full-time pro
Ah... please see my comments above.

Actually dpi does matter. Dpi does not matter when it is not represented on a media, eg. when you talk about resolution of the pic. But when you display it on the screen or printing onto paper for example, then dpi will come into play. How big will the picture be will depend on the dpi.

As an example, if you have a picture with resolution 100x100 pixels. If you display this with 100 dpi, then you get an on screen display size of 1"x1". Most of the CRT/LCD displays have density of roughly 72 dpi. However, this density will not be adequate when you print it out, and you will see stairsteps at the edges (similar to what you see on the screen when anti-aliasing is off) - less dots per inch => larger dot size => more obvious stairsteps. For printing, 300 dpi would be about just right.

7. ## Re: how many pixel is good for a 4R printout?

Agree ... dpi does matter
of cos the skill of the printer helps but only abit
I have had wallpaper size photos printed out i.e. 800x600
but the photo looks great.. even tho the printer warned me the pic might be soft.. cos of low res
but actually truth be told sharpness is a human/relative thing..
not sure of this but you can check out lens sharpness tests factors...
but yeah as i was saying
the photo was a nature shot with background blurred except for the central animal
so a certain softness was expected.. but cos of the blurred background i guess.. the slight softness in the photo didn't matter..
but the printer can acutually resize the photo and use unsharp mask..

8. ## Re: how many pixel is good for a 4R printout?

Why don't you burn everything to a CD and duplicate the CD to the no of copies u require? Then meet them up and pass it to them. Anyway, CDs are cheap. It is a waste of time to download the photos from the internet. And to develop the photos, higher pixel density, higher quality. Why compromise? Max up the pixels!

9. ## Re: how many pixel is good for a 4R printout?

Originally Posted by Poopy
hello people
my 9MP camera give me a 3488x2616 - 72dpi - image size

i want to reduce the file size as it is too big to be sent to alot of people and they just want to print them out in 4R.

What is the recommeded size for a good, sharp, 4R size photo?

with 72dpi.. what "??? x ???" should i put use?

thank u =)
200dpi is good for photolabs and home printers. (200dpi * 6 inch) X (200dpi * 4 inch) = 1200 * 800.

10. ## Re: how many pixel is good for a 4R printout?

2 MP is enought for a 4R print...

11. ## Re: how many pixel is good for a 4R printout?

Originally Posted by Goldenstars08
2 MP is enought for a 4R print...
Indeed. That was what they all told us when the new 2 MP cameras were the craze.

I find that there is a tendency for people to demand more and more from digicams and the technology. People are always upping their standards. People might even feel that you need 5 MP for a decent 4 X 6 inch print. Pshaw!

I've read books that recommend printing images in at least 200 DPI, if not 250 DPI. The trick here is to optimize your image for the output that is required.

If you have Adobe Photoshop, open your image, then go to Image Size. Uncheck Resample Image. Notice that the document size is given in inches. Continue to increase the pixels/ inch number until you get a measurement that is only slightly larger than 6 X 4 inches. Click OK. And then you'll have it...an image optimized for printing on the size of document that's required.

Remember to choose 'Save As' for this new image. Based on your 9 MP image, you should be able to go as high as 400 pixels/ inch.

12. ## Re: how many pixel is good for a 4R printout?

Originally Posted by Goldenstars08
2 MP is enought for a 4R print...
I've printed a 800x600 picture into 4R. No one could tell what the original dimensions were... 800x600 = 0.48MP

13. ## Re: how many pixel is good for a 4R printout?

Originally Posted by Watcher
I've printed a 800x600 picture into 4R. No one could tell what the original dimensions were... 800x600 = 0.48MP
Ditto!

14. ## Re: how many pixel is good for a 4R printout?

Originally Posted by +evenstar
1728x1152 should be enough...not sure how to do the calculations so i simply took
6"x4"x72dpi=1728
1728 * (2/3) = 1152
incorrect calculation.... 6"x4" is area of 4R size paper.... it's two dimensional, not to be mixed with a single dimension measure like length.

15. ## Re: how many pixel is good for a 4R printout?

image from my 1.3MP cam produces sharp enough (not pro requirements) prints at the lab. but i think better to have 2mp worth for better results (i.e. minimum 1600 x 1200).

However if your pics are very well taken (at origin), then like they say, 800x600 may the only requirement. think there is indeed such a recommendation pasted at the lab when you send for printing.

16. ## Re: how many pixel is good for a 4R printout?

4" at 300dpi = 1200px
6" at 300dpi = 1800px

the dpi does not matter as long as the pixel count is there

17. ## Re: how many pixel is good for a 4R printout?

Under normal lighting conditions and at normal reading distance, 1/6 mm is about the accepted smallest point in print that can be clearly discerned by an average person. That translates to 6 lines pairs per mm = 152 line pairs/mm = about 300 dots per inch.

So in terms of digital image resolution, if you need to print 4" x 6" without observable loss in quality, then you would require

4" x 300dpi = 1200 pixels
6" x 300dpi = 1800 pixels

= about 2.16 mega pixels in digital image.

So you may want to resize your image down to about 1800 x 1200.

The actual file size in megabytes depends on your bit rate and compression used.

==========
Generally, 240-300 dpi is acceptable.

If 240 dpi, then your required digital image would be
4" x 240 = 960 pixels
6" x 240 = 1440 pixels

= about 1.4 mega pixels.

===

dpi does matter in print.

If you view it a distance much further than reading distance, then the required dpi would be much lower.

====
All you need to do is to resize the image down according to your desired dpi printing. The dpi setting in your digital image doesn't matter because it will be left to the person who is printing it to set it later. If you have sent him a 1800 x 1200 image and he wants to print 6" x 4", then the dip would be automatically set at 300 dpi. If he specifices the print to be larger than 6" x 4", then the dpi would be automatically be lower and there may be a loss in picture quality, depending on other factors.

18. ## Re: how many pixel is good for a 4R printout?

Originally Posted by Watcher
I've printed a 800x600 picture into 4R. No one could tell what the original dimensions were... 800x600 = 0.48MP
Agree. I've got quite a number of photos from my 2MP camera printed by photolab at 4R with great result. I don't think anyone will be able to easily differentiate whether the pictures were printed from film or digital. It was not at the maximum pixel setting and the file size translates to about 350 to 400 kB. In fact, in my office for our reporting purpose, we use the lowest image quality setting that translates to file size of about 100-150kB. The printouts are quite good for 4R size.

19. ## Re: how many pixel is good for a 4R printout?

Megapixel and file size are related but separate issues.

File size depends on the compression used and what the picture contains (the mix of dark vs bright pixels and continuity of colours).

I can easily have a 2MP (e.g. 1600 x 1200) picture at a file size below 200KB if the compression is high. Try using Windows Paint to save a 2MP picture and you will see what I mean. There may or may not be any observable loss of picture or color quality.

But when it comes to printing, dpi comes in and the quality of the printer also counts. The dpi achievable is directly related to the pixel counts of the picture. To the non-fussy, 150-200 dpi might still be acceptable in print.

20. ## Re: how many pixel is good for a 4R printout?

don't know wat u guys think, but i've done 4R prints at a resolution of only 640X480(thereabouts) at 72DPI.
the fotos are sharp.

normally, i will simply bring my prints(1800X1200, 72DPI) down to Kim Tian and look for Michelle or PeiYun and requests for 4R Fill-In(something like tat la) printing.

never understand the technical jargons that well, but i've done 15R fotos at only 72DPI.

i mux haf missed out alot of technical jargons along the way...

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