In video, DPI is meaningless. Ignore it completely. All that matters is the frame's dimensions.

1080 is not LPI. 1080 is vertical frame size. If 1080 was the LPI of the image then your HD screen would only be 1 inch high!

chien,
when rendering a 3d animation, doesnt dpi matter for the clarity of the image?

so should I worry about the image size.

In other words I rendered it at a step down ratio (cant remember but its like 780x420) or something like that.

If its true that 1920 is the pixel size of widescreen then should I render my images at that ratio and will that help the image be clearer.

Aug

dpi doesn't mean diddly. Ignore it. Purge it from your mind.

All that matters are the pixel dimensions of the image. HD 1080 is 1920x1080 in square pixels. Set your rendering software to that frame size.

780x420 at 72dpi is 780x420. 780x420 at 300dpi is still 780x420. 780x420 at 7200dpi is still 780x420. dpi is meaningless.

The only time dpi matters at all is when you are scanning from a printed original or printing the output to paper. Since neither of those is involved when going from your animation software to video, dpi is meaningless.

Did i say that enough times? Let's go for one more ... dpi is meaningless. ;)

Dots per inch (dpi) isn't useful, as Kelly has already stated, but it CAN be converted to something useful. What is useful? The measure of the total pixels in your video frame, still photo file, or other image.

There are two common ways to express the total number of pixels:

1. Give the number of pixels in the horizontal direction and also the number in the vertical direction. For instance, NTSC DV 4:3 video is 720 pixels by 480 pixels.

2. Give the total number of pixels. This is simply the result of multiplying the two numbers given in #1: 720 x 480 = 0.346 megapixels. Digital still photo cameras are usually specified in this terminology.

Now, in printing, dots per inch is often used, because to make a picture look good on a piece of paper, you have to stuff a certain number of dots into each square inch of paper. If you don't, the picture looks grainy, like newspaper. Based on how your eye perceives things, and on the technology of printing, it turns out that pictures start to look pretty good when you put about a 150 dots (horizontal) by 150 dots (vertical) into each square inch.

Now, with that as background, here is how you can convert dots per inch into one of the two measures (#1 and #2) that are useful when dealing with video: you simply multiply the dpi times the size of the image. So, if you scan a physical photograph (using a flatbed scanner, for instance) and you scan at 200 dpi, and the picture is a 4x6 photo, then the total pixels is 200 times 4 = 800 by 200 time 6 = 1200. Thus, the resulting file will be 800x1200 (or 1200x800, depending on how you rotate the image) and the total pixels will 800x1200 = 0.960 megapixels.

Thus endeth today's lesson. There will be a test at start of class tomorrow.

guys,
I rendered an image in 1920x1080 and it comes up shy on screen by about 40 lines of res.

If I render the image at 1980 then it fills the whole area???

I am using the sony video preview in vegas 5 with the preview and project properties both set to 16:9. Yet the 1920 width comes up short...

Are you sure you didnt mean 1980x1020?
It perfectly filled in when I rendered the 1980???

Aug

You have too many pixels in the X direction, so Vegas truncates.

720/480 = 1.5

1980/1080 = 1.83

If you want the picture to look exactly the same, it has to be scanned at 1620 x 1080. Otherwise you will have to stretch to fill (in which case the picture will be distorted) or crop it (in which case you will lose image on the left and right side of the original picture).

I guess I'm confused.

I was told that 1920 x 1080 is the pixel resolution for wide screen yet when I render at this resolution I have black area on both left and right in my preview.

I then found that 1980 filled in the whole area.

Now I've got the last post stating that 1620x1080 is the correct size?

Which is it : )

?

Well, actually anything from 1x1080 to <infinityx1080 is correct, depending on the pixel aspect ratio. 1920x1080 is correct if you have square pixels (PAR of 1.0). I suspect your problem is that somehow you don't have square pixels. 1980x1080 would fit if your PAR was 0.9697. 1620x1080 would fit if it was 1.1852. You may want to check whatever is producing your original images and make sure it's saving with square pixels.

chien,
I am rendering the 3d image at par=1 resolution 1920x1080.

if the whole image is red then vegas will show blank area (black background) on both left and right sides.

I'll double check in my 3d prog and I'll post there to see if anyone has any advice.

I'll update in a few days.

Aug

ok I found that if I set the "template" in the project properties to HD widescreen the 3d video fits, however

the still image (same res) 1920x1080 now shows black borders on top and bottom :(

I'm confused helllllp :)

Aug