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Resolution for still photos in HD video

galactustrilogy's picture
Last seen: 2 years 6 months ago
Joined: 01/21/2012 - 3:01am

I've seen recommends for pixel sizes for still photos imported into HD video, but not the PPI. So if I import a still photo in Premiere at around 1980 x 1200 or so, what PPI? 72? 300?


Woody Sanford's picture
Last seen: 2 months 2 weeks ago
Joined: 10/19/2010 - 7:33am
Plus Member

Many of times I've taken frame grabs to work with that go back in the video and even HD is always 72dpi. Sometimes I can see a difference in quality going higher but not always. You don't always have to hit the print demands of 300 either, sometimes just a jump to 150 is all you need. Its something you have to play by ear/eye and how much you influence detail with it. I wouldn't mess with it on a close up with tons of detail.

I shoot in RAW with my still cam, so everything I work with is usually 240 dpi to begin with.


Charles Schultz's picture
Last seen: 1 year 3 months ago
Joined: 10/25/2010 - 10:38pm

If you have it in 300 PPI go with it but don't try to take a 72 PPI and uprez it to 300 it will look like crap, for a lack of better terms.


Yvon Robert's picture
Last seen: 1 year 2 weeks ago
Joined: 10/17/2010 - 1:35am

Hi,

Consider that a photo or image has 2 factors: canvas size and picture size normally both factor are equal. In HD the picture and canvas are 1920 x 1080 pixels at 72 dpi.

What is DPI (dots per inch) more dpi more quality in but the quality can cause problem as example computer screen can use 72, 96 or 120 dpi. but to print a high quality on common printer you need at least 150 dpi or 300 or 600.

You cannot use a 300 dpi and reduce to 72 and after go to 300.

What you can do?

Your screen is 1920 x 1080 a full screen picture can be reduced or fit to1920 at 120 dpi.

A PIP picture may be 50% of the height 540 pixel can be reduced to 540 at 120 dpi.

Use PhotoShop or any good drawing program to rescale your picture or photos.

Regards,

YR


galactustrilogy's picture
Last seen: 2 years 6 months ago
Joined: 01/21/2012 - 3:01am

So if I understand this, the ppi could be a little on the high side, say 150 on an image that measures 2900x1200 or so, for use in HiDef video...but 72 is probably ok? I have no intention of upconverting 72 to 300, but thanks for that advice. Many thanks!


Woody Sanford's picture
Last seen: 2 months 2 weeks ago
Joined: 10/19/2010 - 7:33am
Plus Member

When its higher I just scale down and never had adverse effects from that. I agree, upresing is a bad choice. Most of the time though, I don't pull out the still to get a high res RAW image and just pull a frame grab if I need a still to use. I shoot progressive and the 72dpi is usually enough. With that said, I agin have only seen a difference in close up high detail images and on my still cam a lower quality has been enough, 150-240dpi has been more than enough and I've never needed 300dpi. It just never made any improvement.


Jaimie's picture
Last seen: 1 year 5 months ago
Joined: 10/14/2009 - 1:25pm

I have fought the battle of putting stills in video a number of times and have come to the conclusion that dpi doesn't matter.

In still printing, you know the size of your output format and would normally scale your final to 300 dpi which has become sort of a standard. Of course, you're not stuck with 300 dpi, but let's use it for discussion's sake. For example, if your output will be an 8x10" print, at 300 dpi your file would be 2400x3000 dots or about 7.2 megadots or megapixels whatever you like to call it. Assuming your printer and paper can support that resolution, that will give a darn nice looking photo.

But, in video, you don't know the viewer's screen size, or even it's resolution. What you do know is your project's resolution. Let's say it's 1920x1080, a common standard. Notice that is only about 2 megapixels and that's as good as it gets! To see what the displayed dpi is, calculate the screen dimensions for the desired screen size and divide the width by 1920. That tells how "thinly" the pixels must be spread to fill the screen area. These are: 32" diagonal screen is about 28" wide by 16" high which gives about 69 dpi; a 40" diagonal screen gives displays about 54dpi and the whopping 80 incher comes in at 35dpi. What a shocker and that's HD! The numbers are all approximate because TVs don't necessarily display all the pixels (hence the "safe areas" in Premiere).

TVs uses various smoothing tricks to make the picture look better than these numbers might indicate. But then, too, viewers don't usually sit a foot away from an 80" screen. All that said, what's the bottom line?

My personal experience is that a 3 to 5 megapixel photo scales nicely in Premiere. If you give it a 50 megapixel photo, it sometimes coughs up a hairball.

But wait, there's more. Close-up photos with few details look better on screen than long views filled with fine details. I have also noticed, especially when you edit in HDV, but reproduce on a standard DVD, that making the photo move slightly improves its appearance. I often have the photo "swell" about 10% or move a small amount. This seems to result in cleaner edges.

That's it for now,

Jaimie


birdcat's picture
Last seen: 1 year 10 months ago
Joined: 10/21/2005 - 10:09am
Plus Member Moderator

DPI/PPI is irrelevant in video - It is used only in print work. Video is based on pixels only, no per inch. Images for video should be sized using 72 DPI - 72 DPI and 400 X 300 is the same as 144 DPI and 200 X 150 - both equate to 28800 X 21600. NTSC SD is 720 X 480 and HD is 1920 X 1080 or 1280 X 720.

Bruce Paul 7Squared Productions http://www.7squared.com



EarlC's picture
Last seen: 3 months 1 week ago
Joined: 10/15/2008 - 1:15am
Plus Member Moderator

Notwithstanding the print resolution of my stills, I always scan stills at 150-to-300 dpi, primarily because one or more of them WILL get printed as I use them for insert sheets and DVD/CD cover art. My other purpose for scanning at print resolution is to provide me with enough image information that I can zoom in on many of the images, starting from a full-frame or partially cropped area, getting close to and isolating a specific point of interest, or person in a group. Not too swift, trying to do that with a 72 dpi image. I used to setup my NTSC SD framing in Photoshop but now have a program that handles that for me so I don't have to worry about computer & print square pixels vs TV rectangular pixels. Just some more stuff to think about in working with stills in a video project, or photo montages.


D0n
D0n's picture
Last seen: 1 month 3 weeks ago
Joined: 11/09/2007 - 5:28pm

another place where image size for stills matters is when cropping or panning or applying Ken Burns styled motion to a still image...

I always prefer 6 to 16 mp stills off my d-slrs for adding into my video projects.

This way I have endless options in post.

one example, is using an ultra wide still of a static scene and panning across it in final cut as opposed to panning it with the video camera... much easier for say a wedding production where you need your video camera to remain framed and focused for the close up on the bride and groom, but want a pan of the whole church for a cutaway...


birdcat's picture
Last seen: 1 year 10 months ago
Joined: 10/21/2005 - 10:09am
Plus Member Moderator

Earl brings up a very good point - If you're gonna do the "Ken Burns" effect, you want to be able to zoom in without losing resolution. You just need to be careful because some NLE's are not very good at down-resing high-res files (like 16 mpx, considering HD is only 2mpx) and you can get some problems (like flicker). If you are having problems with the high-res stills, you might want to use something like PhotoShop to down-res them to something like 3-4mpx first.

Bruce Paul 7Squared Productions http://www.7squared.com