Masked Images, Video and Resolution…

kentwolf wrote on 2/18/2004, 12:05 PM
Just needed some opinions here:

I am using Vegas 4.0. I have found that the biggest factor to making my (masked) digital camera pictures look good on video is lowering the resolution. This has a huge effect and does more than broadcast colors, color levels, etc. I have searched for and tried everything in this forum; tried it all, and finally determined that apparently, lowering the resolution is key.

I am using Photoshop CS *.PSD images masked with Mask Pro 3.0 plug-in.

With that being said, I found a tutorial on making Photoshop images ready for video (Premiere). This states to make the image resolution 72 DPI.

My native 3.1 megapixel images are something 230 DPI. Lowering them to 72 DPI makes them look much, much better; especially around the (masked) edges.

Question: Is there something “magical” about the 72 DPI value? What if I can get away with maybe 100 DPI? Is this OK?

I am essentially wondering if there is a “standard” resolution value, such as “72” DPI with which I should stay, or is it OK to use the lowest value that looks good via Vegas 4.0 and an external monitor.

(Using an external monitor is a HUGE help on this issue.)

Thanks!

Comments

farss wrote on 2/18/2004, 12:24 PM
DPI is irrelevant in Video, all that matters are the number of pixels!

What masking are you applying and why?

I suspect the problem with the edges may be due to the shift in levels causing ringing on the composite feed to your monitor. There are much better ways to fix this than lowering the resolution of the still image itself..

One thing to try would be to not use a hard edged mask, create a mask with a slight soft edge in PS, save as PNG to get good alpha depth and then use that in Vegas.
kentwolf wrote on 2/18/2004, 12:32 PM
>>DPI is irrelevant in Video, all that matters are the number of pixels!

Perhaps I mis-spoke. I am referring to the image resolution.

>>What masking are you applying and why?

Masked images of people. So as to remove all else besides the person.

>>I suspect the problem with the edges may be due to the shift in levels
>>causing ringing on the composite feed to your monitor.

This is carrying over to physical DVD media. It does not appear at least to be a preview issue.

>>There are much better ways to fix this than lowering the resolution of the
>>still image itself..

I would love to hear them! :) So far, the resolution thing is the only thing that has helped.

As I previously said, the Adobe tutorial did state to lower the resolution, be it good, bad, or whatever.

What else would you suggest?

>>One thing to try would be to not use a hard edged mask, create a mask
>>with a slight soft edge in PS, save as PNG to get good alpha depth and
>>then use that in Vegas.

I am using a soft brush edge.

I will try PNG and see how that goes.

Really. if you have anything else to suggest, I would be glad to give it a try.

Thanks for your help!
Chienworks wrote on 2/18/2004, 12:48 PM
There can't really be anything significant about 72dpi because dpi really is irrelevant in video. Your original pictures are probably something like 2048x1536 pixels. You are reducing them to something like 640x480. These values are what is important and it doesn't matter if they're 72dpi, 230dpi, 15,000dpi, 6dpi ... or whatever. All the dpi measure does is determine how large the picture will be when it's printed on paper.

The only thing i can think of that would make your masks work better is that resizing the pictures smaller may make the edges smoother and effectively anti-alias them. This would allow the edges of the mask to blend in with the background image better.
farss wrote on 2/18/2004, 1:27 PM
Sorry,
my previous post must have seemed way off the mark but I didn't have a clue as to what you were dealing with.

I think what is happening is reducing the res is causing Vegas to resample the slightly lower res image and in particular the edge causing it to 'bleed' and hence make it less obvious. This is just a guess but makes sense to me at least.

So if I'm right then you'd like to get the same effect on the edge without sacrificing the res on the rest of the image. You could do this with two copies of the original and an extra mask so that the low res image was only used at the edge and the hi res one for the rest but that is getting rather complicated.

Just a thought here, have you tried bringing the image into Vegas with a hard edge and the apply a soft edge FX there. This may work better. I think maybe what is happening is the hi res soft edge you created in PS cannot be correctly resolved by Vegas, I doubt it uses sub pixel sampling, it'd just look at the alpha value of the nearest pixel and use that in its calcs.

But now here's anothr thought, unless you're using pan or zoom there's no reason to have the res higher than 720x480 is there? At that res the pixels at the edge should line up with what Vegas is sampling at, maybe this would work better.

Somehow I doubt if any of this is going to be of any help, just throwing a lot of ideas up in the air and thinking out loud.
kentwolf wrote on 2/18/2004, 2:36 PM
>>I think what is happening is reducing the res...causing it to 'bleed' and
>>hence make it less obvious.

Basically, the image goes from jagged/erratic/non-smooth lines to looking good with the resolution reduction. The image still looks very good with respect to resolution. I believe I was originally at a far higher resolution than the TV/external monitor can display, thus my problem.

>>So if I'm right then you'd like to get the same effect...but that is getting
>>rather complicated.

I think I know what you are saying, but it's looking good with just the resolution reduction.

>>Just a thought here, have you tried bringing the image into Vegas with a
>> hard edge and the apply a soft edge FX there.

No, I did not, but I will try when I get home.

>>I think maybe what is happening is the hi res soft
>>edge you created in PS cannot be correctly resolved by Vegas...

I remember reading something in this forum basically about digital images being "too good" for the relatattvely low res TV screen. That certianly sounds reasonable.

>>But now here's anothr thought, unless you're using pan or zoom there's
>>no reason to have the res higher than 720x480 is there?

No. Actually, when I am changing the resolution, the image is also resized. I do not remember the values. It looks like tweaking the resolution is just another way of resizing it. I am by no means a Photoshop expert, but I am working my way through this. :)

It looks like it all may come down to image resizing.

>>Somehow I doubt if any of this is going to be of any help...

It certainly is a help and I appreciate your time. There's always something to learn... :)

Thank you very much!
kentwolf wrote on 2/18/2004, 2:37 PM
>>...There can't really be anything significant about 72dpi because dpi really
>>is irrelevant in video.

I believe I meant to say Pixels per inch, in other words, resizing the image... :)

Thank you very much for your input!
MUTTLEY wrote on 2/18/2004, 4:08 PM
All of the stuff for the Valentines Video was done in Photoshop. You going to be at the chat tonight ?

http://mediasoftware.sonypictures.com/forums/ShowMessage.asp?MessageID=254031&Replies=5&Page=1

We can talk about it a little more, not sure if I can help but always willing to try.

- Ray

www.undergroundplanet.com

Chienworks wrote on 2/18/2004, 4:47 PM
Well, dpi or ppi, still doesn't matter. It's the "per inch" part that is irrelevant. ;)
kentwolf wrote on 2/18/2004, 6:14 PM
Well, I tried saving the PSD file as a PNG and I also tried the soft edge FX effect.

Still had jagged mask edges until resolution was reduced.

Just FYI.

I would be glad to hear any other suggestions.

Thank you all so much for your input!