Dumb resolution question

divamum

How do I know the dpi of a processed, cropped shot? I have PS and LR (in case there's somewhere to look in the software to tell me!)

Thanks in advance!

CynthiaM

divamum wrote:

How do I know the dpi of a processed, cropped shot? I have PS and LR (in case there's somewhere to look in the software to tell me!)

Thanks in advance!

Do you want to know dpi (I think it means dots per inch or ppi (pixels per inch)?

divamum

CynthiaM wrote:

Do you want to know dpi (I think it means dots per inch or ppi (pixels per inch)?

I've alwasy assumed it means dots per inch. I can obviously tell the pixel size of my image, and I can tell the aspect ratio. But how do I find out how many dpi an image contains when I'm not the one printing it? (I've been asked to submit an image of at least 300dpi for reproduction in a program, hence the question)

pathfinder

Madelaine, don't worry about ppi. Just see how many pixels you have on the long and short margins.

In Photoshop Image > Image Size -> the image size in pixels in the height and width. It will also state the Resolution in ppi, but who cares.

In Lightroom, hit the "i" key and you will see white text over the image in the center pane in the Library or Develop mode. You will see the image size in pixels along the long and short margins. PPI is not displayed. Hit the "i" key a second time and up pops the exif data and the lens used for the shot including focal length. This information is displayed in the upper left corner of your image. I just leave the exif data on all the time.

PPI - pixels per inch refers to image resolution. DPI refers to how many dots of ink per inch in a printed image. There may be anywhere from 5-15 dots of ink per each pixel with a modern, pro level 8-12 inkset, inkjet printer.

Someone specifying they want their image in 300 dpi, really are not quite accurate. I am sure they want 300ppi, not dpi. You do see the term dpi used not infrequently, but incorrectly unless describing a printers capabilities. Most modern printers print 1440 or 2880 dpi ( at least my Epson does). 300 dpi would be a very weak sister to those printing resolutions.

divamum

Thanks PF. All of which leads me to the question... what's the minimum pixels per side my image should have to conform to what they think is dpi (even if they really mean ppi)? Again, this is a digital copy of a photo being submitted to be included in a program, thus I have ZERO control over the printing process -once it's left me, it's entirely out of my hands (especially since this is submitted for my incarnation as a singer, not a photographer!!! )

While I'm pretty proud to have finally achieved shooting my own headshots this time out (although man, it's hard when your trying to be on both sides of the lens!) this final prep stage is making me NUTS. Love shooting. Love processing. Haaatteeee preparing for print, especially since my own involvement in the photographic process on this occasion needs to be transparent (ie, nobody CARES about my opinion as a photographer - they just wanna see pretty promo pictures in their brochure )

pathfinder

You really need to know the final image size they want to print, and then make sure your total pixels are sufficient at 300 ppi to match their image size. ( The trick is they may not actually know what size images they intend to print - so they tell you 300dpi not realizing you cannot know how many pixles to provide at 300ppi without knowing the desired image size )

In other words, if they want a final image 10 inches tall after printing, you will need 3000 pixels to provide 300ppi for 10 inches. 10 inches x 300 pixels/inch = 3000 total pixels.

divamum

pathfinder wrote:

In other words, if they want a final image 10 inches tall after printing, you will need 3000 pixels to provide 300ppi for 10 inches. 10 inches x 300 pixels/inch = 3000 total pixels.

Well duh - even my mathematically-challenged self should have figured out THAT particular calculation

I suspect these will be tiny - like 1x2" - so I'm not going to sweat it too much. Thanks!

Richard

divamum wrote:

Well duh - even my mathematically-challenged self should have figured out THAT particular calculation

I suspect these will be tiny - like 1x2" - so I'm not going to sweat it too much. Thanks!

The key point to remember is that dpi/ppi is not an attribute of an image. The image only has pixels, not inches. Dpi/ppi comes into play when the image goes to an output device like a screen or printer. These devices do have limits on how many pixels per inch they can display or print, but in general, that's not something that you can control. If the pics will be printed very small, you needn't be concerned.

pathfinder

And that is why I find the the vendor requiring 300 "dpi" so funny, Richard.

divamum

pathfinder wrote:

And that is why I find the the vendor requiring 300 "dpi" so funny, Richard.

Indeed. I think things like this were easier when I didn't want/need to know what folks were talking about... I just pulled an 8x10 off the pile I'd had repro'd at ABC (lithos - GREATand affordable mass reproduction for performers) and stuck it in the mail

In any case a short article of relevance which may help somebody else down the road, so here's the link http://malektips.com/digital_photo_printing_0004.html

Thanks again!

pathfinder

Once again, the article talks about dpi rather than pixels per inch!:D

Once again, dots per inch is what inkjet printers provide, based on the PIXELS per inch available in the image. Typically they will print 5-15 dots of ink per each image pixel!!

justus

Resolution
Lightroom 2 also lets you export at whatever resolution you dictate. For example, I have exporting presets "set up" for sending photos to different places. For my blog, I preset at a higher resolution, but smaller size photo. For magazine clients, I preset at 300ppi, larger size photo, etc. So, if your client is asking for a 300ppi photo, even if you've cropped and edited it, you can export to their specifications.

Whenever you export a photo in LR to send to a folder, you can dictate those parameters. Hope that helps.

divamum

justus wrote:

Lightroom 2 also lets you export at whatever resolution you dictate. For example, I have exporting presets "set up" for sending photos to different places. For my blog, I preset at a higher resolution, but smaller size photo. For magazine clients, I preset at 300ppi, larger size photo, etc. So, if your client is asking for a 300ppi photo, even if you've cropped and edited it, you can export to their specifications.

Whenever you export a photo in LR to send to a folder, you can dictate those parameters. Hope that helps.

Very helpful - thank you!!

Art Scott

pathfinder is correct that dpi=dots per inceh and is for printing and that ppi = pixels per inch..............however the reason 99% of the people that use dpi in the place of ppi are schooled that way......I had asked several printers what is the difference between dpi and ppi and was told it is virtually the same ...... I posed the same question to differnt people at camera stores and was givent the same answer........and then when I got photoshop and I went to IMAGE>Image size.....I notice that under resolution it gives it in DPI not ppi.........

The reason a lot of people ask for files in a certain resolution as "300" DPI is that even ADOBE gives resolution as DPI and we all know thatbow adobebow is the "FINAL WORD" in all digital photographics................