Photo Resolution? at DVinfo.net

Howard Churgin · December 18th, 2008, 09:45 PM

I want to import some photos from photoshop into a hdv timeline. I set up a 1440x1080 page but what is the best resolution to use for the hdv timeline. For sd footage i normally use 150dpi. I think 72 looks bad when I make a dvd and play on hd widescreen set. How high should I go on this resolution?

What would you use if it were for Blu-ray?

Tripp Woelfel · December 19th, 2008, 04:58 AM

Quote:

Originally Posted by Howard Churgin

What would you use if it were for Blu-ray?

That can depend upon your NLE. I know that Premier Pro CS3 works best when the image sizes are near screen res. You can go bigger if you want to do any panning and zooming.

The dpi you set in Photoshop doesn't matter. Video is always 72dpi. Full stop. I have no idea why changing the dpi effects the image quality on DVD. It shouldn't matter.

Can you explain what about your still images looks "bad"? Describing what you are seeing will help us understand your situation more clearly.

Howard Churgin · December 19th, 2008, 05:47 AM

They never seem as sharp at 72. They start to look better at 150. I see what your saying about 72 and I will try it this weekend again.

Thanks

Jon Shohet · December 19th, 2008, 08:44 AM

dpi, or dots per inch, is a metadata value written into the file that affects the behaviour of the printer. It has nothing to do whatsoever with video resolution.

The confusion is maybe because in it's default setting, when you change dpi in photoshop, it also resamples - it resizes the resolution of the file (the actual pixels). Notice that if you turn off resampling, changing the dpi will not affect file size/pixel resolution.

A computer screen is indeed 72 ppi (pixels per inch) but you do not need to "match" dpi to ppi. In fact, video softwares like Premiere and After Effects completely ignore the dpi value written in the file.

What you need to do is save a copy of your original photo, and resize it to 1920x1080 pixels, which is the square pixel equivilent of 1440x1080 hdv.

cheers.

Howard Churgin · December 19th, 2008, 03:18 PM

do I use 1920 x 1080 or 1440 x1080 with pixel aspect correction? I am not clear on this "aspect" (no pun intended)

Tripp Woelfel · December 19th, 2008, 06:18 PM

The cleanest way in theory would be to use the same PAR as your project. So if it's an HDV project, for the pictures to match they would need to be reformatted with that PAR.

The only time I used hundreds of pictures in a project, I created an automation inside Photoshop to convert (down res from a 6MP still camera and change the PAR to .9 for a DV project. If you have Photoshop, that might be one of the easier ways to do the conversion.

Jon Shohet · December 20th, 2008, 01:34 AM

Sorry to contradict Tripp on this one...

You are working with Photoshop and a still image, which was captured as square pixels. if you resize to 1440x1080 square pixels and then assign 1.33 hdv PAR, you will be streching your horizontal pixels.

Cleanest way is to stay with the original square pixel PAR, in this case 1920x1080. When you import to PP, it should interpert correctly (it always does for me) that the still image has square pixels, and when you place it on an hdv timeline it will be exactly the same size as your 1440x1080 1.33 PAR footage.

Of course the other issue is that most still cameras capture 4:3 or 3:2 proportioned frames, while hdv is 16:9. Unless your still image comes from one of the few cameras that can shoot a 16:9 frame, some cropping of the original still frame is necessary to achieve the correct frame proportions.

Jon Shohet · December 20th, 2008, 01:54 AM

What you are looking for, is to match DAR (Display Aspect Ratio) of your different sources.

DAR = [horizontal pixels] X [PAR] / [vertical pixels]

In this case :

1440x1.33/1080 = 1920x1/1080 = 1.78 = 16:9

hope this helps.
cheers.

Tripp Woelfel · December 20th, 2008, 05:02 AM

Quote:

Originally Posted by Jon Shohet

Sorry to contradict Tripp on this one...

Cleanest way is to stay with the original square pixel PAR, in this case 1920x1080. When you import to PP, it should interpert correctly (it always does for me) that the still image has square pixels, and when you place it on an hdv timeline it will be exactly the same size as your 1440x1080 1.33 PAR footage.

Jon's approach makes sense and would be a lot easier than what I suggested. When I did my picture project in PP CS3, Premier didn't conform the pictures to the DV projects PAR. They kept their 1:1 PAR. It's more than likely that I had a setting wrong somewhere.

December 18th, 2008, 09:45 PM	#1
Howard Churgin Regular Crew Join Date: Nov 2008 Location: Marlboro, NJ Posts: 85	Photo Resolution? I want to import some photos from photoshop into a hdv timeline. I set up a 1440x1080 page but what is the best resolution to use for the hdv timeline. For sd footage i normally use 150dpi. I think 72 looks bad when I make a dvd and play on hd widescreen set. How high should I go on this resolution? What would you use if it were for Blu-ray?

December 19th, 2008, 05:47 AM	#3
Howard Churgin Regular Crew Join Date: Nov 2008 Location: Marlboro, NJ Posts: 85	They never seem as sharp at 72. They start to look better at 150. I see what your saying about 72 and I will try it this weekend again. Thanks

December 19th, 2008, 08:44 AM	#4
Jon Shohet Major Player Join Date: Dec 2007 Location: London, UK Posts: 277	dpi, or dots per inch, is a metadata value written into the file that affects the behaviour of the printer. It has nothing to do whatsoever with video resolution. The confusion is maybe because in it's default setting, when you change dpi in photoshop, it also resamples - it resizes the resolution of the file (the actual pixels). Notice that if you turn off resampling, changing the dpi will not affect file size/pixel resolution. A computer screen is indeed 72 ppi (pixels per inch) but you do not need to "match" dpi to ppi. In fact, video softwares like Premiere and After Effects completely ignore the dpi value written in the file. What you need to do is save a copy of your original photo, and resize it to 1920x1080 pixels, which is the square pixel equivilent of 1440x1080 hdv. cheers.

December 19th, 2008, 03:18 PM	#5
Howard Churgin Regular Crew Join Date: Nov 2008 Location: Marlboro, NJ Posts: 85	do I use 1920 x 1080 or 1440 x1080 with pixel aspect correction? I am not clear on this "aspect" (no pun intended)

December 19th, 2008, 06:18 PM	#6
Tripp Woelfel Trustee Join Date: Jan 2008 Location: North Conway, NH Posts: 1,745	The cleanest way in theory would be to use the same PAR as your project. So if it's an HDV project, for the pictures to match they would need to be reformatted with that PAR. The only time I used hundreds of pictures in a project, I created an automation inside Photoshop to convert (down res from a 6MP still camera and change the PAR to .9 for a DV project. If you have Photoshop, that might be one of the easier ways to do the conversion.

December 20th, 2008, 01:34 AM	#7
Jon Shohet Major Player Join Date: Dec 2007 Location: London, UK Posts: 277	Sorry to contradict Tripp on this one... You are working with Photoshop and a still image, which was captured as square pixels. if you resize to 1440x1080 square pixels and then assign 1.33 hdv PAR, you will be streching your horizontal pixels. Cleanest way is to stay with the original square pixel PAR, in this case 1920x1080. When you import to PP, it should interpert correctly (it always does for me) that the still image has square pixels, and when you place it on an hdv timeline it will be exactly the same size as your 1440x1080 1.33 PAR footage. Of course the other issue is that most still cameras capture 4:3 or 3:2 proportioned frames, while hdv is 16:9. Unless your still image comes from one of the few cameras that can shoot a 16:9 frame, some cropping of the original still frame is necessary to achieve the correct frame proportions.

December 20th, 2008, 01:54 AM	#8
Jon Shohet Major Player Join Date: Dec 2007 Location: London, UK Posts: 277	What you are looking for, is to match DAR (Display Aspect Ratio) of your different sources. DAR = [horizontal pixels] X [PAR] / [vertical pixels] In this case : 1440x1.33/1080 = 1920x1/1080 = 1.78 = 16:9 hope this helps. cheers.