# how many megapixels do i need

Discussion in 'Design and Graphics' started by nicrose, May 1, 2007.

1. ### nicrose macrumors member

Joined:
Apr 11, 2006
#1
i have a client who wants me to do a poster 24" by 36" (Inches). And I have to include a big photo of him in it. If he gives me a photo file, how big will the file have to be in order to print at 300 dpi? I need the photo to fill up the space of the poster. It doesn't have to be a 24" by 36" inch photo, of course, but it has to be big enough to stand out because it's the only image in the poster.
I tried to calculate the Megapixels and I got this rediculous answer: I need a 78 Megapixel image!!! This is how I calculated it:

300 dpi X 24 inches=7,200 pixels
300 dpi X 36 inches=10,800 pixels

7,200 x 10,800 pixels is approx. 77.8 Megapixels

Ummm, I don't think my 6-megapixel camera can handle that!!!

Am I missing something here????

Should I just take the pic with an analog camera instead?? How big can 35mm film be blown up to and still look okay?

I bet this is a dumb question...oh, well, i need to know this!!

2. ### ambient macrumors member

Joined:
Apr 21, 2007
#2
im pretty sure the base model SLR's canon 400d / nikon d80 which are both 10mpx can be blown up to a3 size without losing quality.. you might be better off going film if you are gonna do something this size with a small format camera...

otherwise, look at medium and large format cameras such as the Hassleblads if you actually want that much megapixels...they can go up to 50mpx i think

maybe consider a professional photographer

Joined:
Oct 11, 2004
Location:
On the Left Coast - Victoria BC Canada
#3
Well of course you need as good a photo as you can get BUT...

Talk to the printer who is going to be outputting the job and ask THEM what resolution you will need.

Typically the resolution of your finished artwork, size-as, needs to be 1.5 to 2 x the halftone line screen of the printed output. Any higher a resolution is wasted.

So of the poster is being printed at 120 line screen, then the art needs to be 180 - 240 dpi

If it is going to direct digital output, like I say, ask the printer.

4. ### failsafe1 macrumors 6502a

Joined:
Jul 21, 2003
#4
There are a few things to consider.

Most pixels you can get and manipulate those.
Shoot a film format that provides more image to work with.
Go with what you have and hope for the best.

Are you sure you need 300 dpi for you poster? Some printers don't produce that if it is not a glossy publication. I am a pro photographer with a coworker that photographs people with their cars using an old Nikon D1 and the Apple poster print. He gets acceptable quality from this with no complaints from his clients. I use the Fred Miranda plug in and Genuine Fractals to scale my photos to larger dimensions than what my Canon 1D and Nikon D2h can provide. Both do an acceptable job. When you enlarge anything past a certain point even with film you see imperfections. The key is normal viewing distance. Your poster may look fine when seen at the normal viewing distance. We have all seen film posters that look horrible on close examination due to grain. My boss is getting ready to upgrade our camera system to the Canon 1D MIII so my file size will increase greatly. We are a news office and do magazines as well as newsprint type pieces. I tried to talk him into the 1D MIII along with a full frame body but our budget would now allow. The Fred Miranda plug in is quite a bit cheaper than Fractals but I prefer GF. It was just updated to be compatible with the Intel machines.

5. ### ATD macrumors 6502a

Joined:
Sep 25, 2005
#5
A 10 to 12 Megapixel camera would produce very good image quality for what you are doing. I have worked on images that were shot with a 22 Megapixel Hassleblad, the detail is so sharp it's almost counterproductive, particularly with head shots. Unless your client needs to see amazing detail within each and every pore of his face you can stop at 12 Megapixel. Head shots done this way take many hours of retouching to get rid of the tiniest flaws.

Also keep in mind that most posters are not meant to be viewed close up (like others have said) and are not always printed at 150dpi from a 300ppi file. For example, movie poster files are built at 150ppi in photoshop, not 300ppi.

Check with the printer before you start building anything.

6. ### ChrisA macrumors G4

Joined:
Jan 5, 2006
Location:
Redondo Beach, California
#6
Yes, you are missing something. You don't need to print at 300 DPI. that is good for a small print viewd are arm's length but a poster is intended to be viewed from some distance. 100 DPI would be OK. Notice that the file size is a function of the square of the DPI. so a 3X reduction from 300 to 100 DPI reduces the file size by a factor of 9. Your 77.8MP number when divied by 9 lands right in DSRL land.

You are making a poster, not a fine art print and 100 DPI is fine. But if you did want fine art print quality you would be best to use a 4x5 view camera. a 35mm film camera is a compromise and really is to small to make a 100 MP file. 4x5 is surprisingly cheap. You can put together a good setup for under \$1K or even for \$200 if you like. Those very inexpensive 50 year old lenses work well for portraits too.

A good rule of thumb is that you can blow a negative up about 16X. I think this applies to DSLR too. For example a 10MP DSLR has a 24mm wide frame. Call it one inch. At most it can make a 16 inch wide print if you push it . A 35mm film camera can do about 24 in wide and a 4x5 view camera might do a 6 foot wide wall mural under best conditions. 12X is a more realistic limit for most images where you don't have \$1K lenses, heavy tripods and cable releases.

7. ### nicrose thread starter macrumors member

Joined:
Apr 11, 2006
#7
hi, everyone

i talked to the printer and he said to send a 300 dpi pdf file of the poster. i asked if 150dpi would be okay, and he said it will be not as good. well, i know that already!! duh! what i need to know is, will it be so bad that it will be unacceptable by design standards?
someone here mentioned that movie posters are all done at 150 dpi. so, i'm thinking, okay, maybe i can get away with doing this poster at 150 dpi, then. when i say dpi, i'm actually referring to the resolution in photosshop, so may be i should say ppi. anyways, i hope 150 ppi works out...it seems to go against everything i was taught in school, but then again school didn't teach me much about the real world anyway.

also, what is the quickest and best way to calibrate my monitor, printer,etc. so that the poster (which will include photos) comes out looking great?

thanks

nicrose
mbp present-my very own computer
imac 2000-06 family computer
several apple IIe in the 90s that were loaners from my mom's school district
commodore 128 in the 80s

8. ### heehee macrumors 68020

Joined:
Jul 31, 2006
Location:
Same country as Santa Claus
#8
If your printer wanted high quality output, he would have asked for a tiff file. 150 dpi is fine for a poster.

9. ### ATD macrumors 6502a

Joined:
Sep 25, 2005
#9
If that's what the printer wants and you will feel better about doing 300, then go ahead. Other than being slow in Photoshop, it can't hurt anything, overkill but no harm done. I will generally give a printer exactly what they ask for, that way I don't get extra charges because I didn't set it up "their way" and if the job runs into problems on the press the printer can't come to me and say it's my fault for not following their directions.

BTW, the printer did say 300ppi at full size, right?

10. ### dogbone macrumors 68020

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S33.687308617200465 E150.31341791152954
#10
When a printer says stuff like this to you, a little voice in your head should say, "this idiot has no idea what he's talking about, he's just spouting off something safe"

Nothing beats doing your own testing. Why not just run out an A4 inkjet or laser print at 300 and 150 and see that you cannot tell the difference. Try one at !00 ppi just to see how it's still quite acceptable.

11. ### nicrose thread starter macrumors member

Joined:
Apr 11, 2006
#11
Dimensions, printer res, ppi, dpi, and how all these things relate is so confusing!

Nicrose says:
You're question is interesting, because it reminds me of something the printer guy mentioned in his email:

"Hello,
the requirements are:
300 dpi
PDF
at least half the dimensions from the final size
thanks"

What does he mean by "at least half the dimensions from the final size".

I want to print a poster that will measure 24" by 36". I would prefer to print it at 150dpi so that I can make a photograph in the poster as large as possible. I don't understand what he means about the dimensions. If anybody understands, please let me know.

To be clear, this will be printed on a large format inkjet printer.

This job has to come out right because it could cost the client hundreds of dollars. This is my first major job and I'm streeeesssssed! I also have color management issues, as you all can see from my other post!!

Nicrose

12. ### ATD macrumors 6502a

Joined:
Sep 25, 2005
#12

That's why I asked, it seems that the printer wants 300ppi at half size which is exactly the same as 150ppi at full size (as we were saying). Once you start printing large pieces it's not uncommon to get mech specs as a percentage of the full size like half size or quarter size. When it comes to billboards you will get specs like 1/2 inch = 1 foot. I would ask the printer to give you a clear idea of what he is looking for, you need to be clear on the resolution and scale needed.

For example Quark 6.5 will not make a file over 48" wide, you have to work in scale for large printed pieces.

13. ### heehee macrumors 68020

Joined:
Jul 31, 2006
Location:
Same country as Santa Claus
#13
As I and many others said, it's fine at 150 dpi if you are printing at 24x36. Save it at that resolution and size. If you want to make sure, print it out at your own printer in colour at full size on 8.5x11 and lay it out side by side.

If you still want to make sure, print one out at the printer, it shouldn't cost more than \$50 at 24x36.

14. ### xfiftyfour macrumors 68030

Joined:
Apr 14, 2006
Location:
Clemson, SC
#14
uhm. just fyi, PDF is becoming a norm among printers, and doesn't at all indicate poor quality if it's created to standards.

15. ### nicrose thread starter macrumors member

Joined:
Apr 11, 2006
#15
pdf is means low quality??

Hi, how come the one guy in this forum seemed to be saying pdf means low quality? It should be high quality if I export the pdf under "press" quality, right?

I talked to the printer and he said full size at 150 dpi would be okay. I can see now why going at half or some fraction of a size would be important. The other day I was in photoshop and I accidentally typed in 10,000 inches or pixels or something in the dimensions field and then I got this message that basically said, okay, if you really want this size, that's okay; but it's not going to open up in any legacy version of PS. And yeah, it's good to know there's a size limit in Quark, too. I love these forums. So helpful. Thanks, everyone.

16. ### xfiftyfour macrumors 68030

Joined:
Apr 14, 2006
Location:
Clemson, SC
#16
Yes, as long as you save it to press quality, it should be good. People who think that PDF = low quality are those that have probably only used it for emailing proofs around an office (which would have been saved as lowest file size, which would be low quality).

Yepp, you can do 150 dpi at full size right from the start, or you can do 300dpi at half the size. Then, once the printer received it, he'd enlarge it to full size and would have the 150 dpi. It's called effective resolution. Either way you'll end up with the same quality, it's just that working with a smaller file will be easier on you and on your computer.

17. ### heehee macrumors 68020

Joined:
Jul 31, 2006
Location:
Same country as Santa Claus
#17
There are pros and cons to either one, but generally, pdfs are compressed, that's why they usually have a smaller file size, that being said, you can compress a tiff file too.

PDFs are great in the document world, text can be selected, searched and emailed because they generally have a small file size.

Since you are doing this in photoshop and have to flatten the image before saving it, text cannot be selected in pdf format, so there is no advantage in that. Saving it in tiff will have a higher resolution and the file wont be compressed. Also, after you save the file in tiff, zipping it will have a smaller file size than a press quality pdf.

18. ### xfiftyfour macrumors 68030

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Apr 14, 2006
Location:
Clemson, SC
#18
Oh god you are so misinformed.

19. ### Father Jack macrumors 68020

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Jan 1, 2007
Location:
Ireland
#19
It's not all down to the pixel count If the lens is crap the image will be as well no mater how many pixels you have.

I have a Leica digital camera with 5.2 Mp and have printed images to A2 which are very acceptable.

FJ

Joined:
Oct 11, 2004
Location:
On the Left Coast - Victoria BC Canada
#20
OK well, when you save as PDF you have all these options:

You can choose downsampling of colour and black and white art (which for this purpose you don't want to do)

You can choose whether to compress or not, and what type of compression to use - JPEG or ZIP. Choose ZIP, it is lossless compression which means that what the printer gets will be exactly the same as what you created.

21. ### AlexisV macrumors 68000

Joined:
Mar 12, 2007
Location:
Manchester, UK
#21
As a rule, a 6 megapixel camera will fill an A4 at 300dpi.

200dpi isn't too shabby for print, and Photoshop can enlarge quite well if you choose bicubic smooth in the image size dialogue box.

It may look a bit blurry at 100% on screen, but it should look fine in print.