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Dots per inch & Pixels debate
Ok, i’m in a debate with a photographer who is excellent at his craft and Photoshop. I’m an editor and great at my craft. Our debate centers around distorted & grainy images used in a non-linear editing application. I’ve always been trained and have used the technique of taking hi-resolution images form a DSLR that are way above 72dpi and reducing them to 72dpi despite the aspect ratio to prevent image distortion when creating slideshows via FCP or Avid. I’ve seen images that are way above 72dpi and used in a DVNTSC timeline flicker, become grainy and shimmer. The photographer is telling me dpi does not matter when it comes to editing images in a non-linear editor. Adjusting the aspect ratio is the only thing you need to change and that dpi has nothing to do with pixels, which I get, but I’ve read and followed directions from DV Magazine, Videoguys, Videomakers, etc. that when working in a DVNTSC project still images need to be at 72dpi or no more than 100 dpi. It has worked for me. So, should I ignore dpi settings in PHotoshop and just adjust the dimensions of the photo from lets say 1920 x 3000 to 720 x 480 or always adjust the dpi as well as the dimensions & set each image to RGB mode?
Ted Irving
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14 Replies
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Your friend is correct … dpi is meaningless with respect to your video work, its a term solely relevant to print resolution. As far as using images in your video is concerned you are only interested in the frame size.
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[ted irving] “I’ve read and followed directions from DV Magazine, Videoguys, Videomakers, etc. that when working in a DVNTSC project still images need to be at 72dpi or no more than 100 dpi. It has worked for me. So, should I ignore dpi settings in PHotoshop and just adjust the dimensions of the photo from lets say 1920 x 3000 to 720 x 480 or always adjust the dpi as well as the dimensions & set each image to RGB mode?”
DPI is only useful for translating a document’s size from inches to pixels or back. Video has no concept of the physical size of the screen — all that matters is the raster size in pixels.
Some non-video applications do look stated DPI metadata to help size images relative to one another, so keeping your DPI consistent may be useful elsewhere.
Walter Soyka
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Dpi means nothing in Video. Pixel size is the only thing that matters.
We use 72dpi only for all our images from Web to HD to film out. Your images need to be the proper pixel size and aspect ratio for your work.
As for the shimmering in a DV timeline, well of course. That’s 5:1 compression and interlaced. Graphics shimmer no matter what.
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So then the shimmering is only an artifact of my computer monitor, but playing out to a DV recorder & confidence monitor, that shimmer should not be present right? If it is present, which I have seen, what alterations can be done to a very large sized image that will reduce any flickering in DVNTSC?
Ted Irving
Content Freelancer
Media Instructor
http://www.tedtv.tv
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To add my two cents,
You are asking for trouble when putting a 300dpi image into FCP. You’ll make FCP crash prone and renders become much longer than necessary and as others have said you’ve gained nothing for your effort. Video apps care about raw pixel count.
Jeffrey Di Lullo
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[Jeffrey Di Lullo] “You are asking for trouble when putting a 300dpi image into FCP. You’ll make FCP crash prone and renders become much longer than necessary and as others have said you’ve gained nothing for your effort. Video apps care about raw pixel count.”
Not quite — you’re asking for trouble when putting a LARGE image into FCP. DPI is totally relative and doesn’t tell you anything about the absolute size of the image. A 300 DPI image doesn’t necessary have a high pixel count: a 1″ by 1″ image at 300 DPI is only 300px by 300px.
See this page in the manual for more on the video at 72 DPI myth [link].
Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog – What I’m thinking when my workstation’s thinking
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Also, it’s worth looking up pixel pitch. Won’t matter in the file itself of course, but the display does matter. That is, all monitors are not equal.
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Last sentence in the manual to the above link:
“even though the dpi setting for your graphics is irrelevant for working with video, keep in mind that many people may still adhere to a policy that graphics for video must be 72 dpi. To avoid confusion with other graphic designers, you can leave your video graphics at 72 dpi. Just know that there is nothing special about this setting.”
I will say that I have had trouble with 300dpi images in FCP (slow renders – crashing – “out of memory” messages). And that changing the image to 72dpi (but not changing the size) HAS cleared up the problem. To me that IS relevant. I’m not saying that anybody is WRONG in this debate. What I am saying is that part of my prep of any still coming into FCP, AVID or any other non-linear editor is to change the dpi to 72. Call me old fashioned, crazy, or even superstitious if you want to, but then if the app does start to get flaky I can immediately rule that out.
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[Fred Miller] “I will say that I have had trouble with 300dpi images in FCP (slow renders – crashing – “out of memory” messages). And that changing the image to 72dpi (but not changing the size) HAS cleared up the problem.”
That’s very interesting to hear. When you’ve seen this fix a problem, was DPI the only variable, or did you also change the file type or compression?
The thing I’m trying to focus on in the DPI discussion is the fact that simply knowing an image’s DPI doesn’t actually tell you if the image will be large enough to use on-screen. It’s not enough to ask for 300 DPI imagery; we need to specify a minimum acceptable size in pixels.
Walter Soyka
Principal & Designer at Keen Live
Motion Graphics, Widescreen Events, Presentation Design, and Consulting
RenderBreak Blog – What I’m thinking when my workstation’s thinking
Creative Cow Forum Host: Live & Stage Events -
This is a great discussion. Glad I posted it. Seems that some of the confusion may begin with the Photoshop image size settings; scale, resize & constrain. If you adjust the dpi of any image the pixels or width & height will change accordingly. So you are really changing the dimensions when changing the dpi, although dpi has nothing to do with video but print. I’ve been following the same guidelines as Jeffrey but the recent posts have provided more insight. Thanks
Ted Irving
Content Freelancer
Media Instructor
http://www.tedtv.tv
tedirving@yahoo.com
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