It's essentially as brighterside points out. Another aspect of it of course is how important is the final video going to be for your personally and how much effort you are willing to put in. From time to time, I know that some of my dSLR shot in 3:2 format are going to be included in with 16:9 video footage and so compose my still images accordingly i.e. I allow enough space for a 16:9 ratio crop in my photo editing application. Sometimes, though, I haven't anticipated this, or forgotten, but try cropping anyway. Most of the time what's been cropped off is more than made up by the fact that I only have one ratio on the timeline.

OK Thanks guys.
I was actually trying to understand the relevance of having differing pixel aspect ratios in projects. Take standard digital camera images (square pixels), load them into standard PAL DVD project, and the program has to "re-draw" (not sure of correct term here) the entire image to 1:1.09 pixels. Then send it to DVD Arch. PAL widescreen, and they have to be re-drawn again to 1:1.46 pixels. The resulting images looks terrible, having lost much of their definition. This is of course without the added degradation caused by encoding/compression. Definitely to be avoided.
The answer therefore seems to be to stay in either standard or widescreen mode for all files, whether stills or movies, through both VMS and DVDA throughout the entire process, resizing/cropping where necessary. Does this make sense?

The only time the image will be "redrawn" (resampled is the correct term) is when it is rendered into the final usable video file. Regardless of any match or mismatch between all those aspect ratios of media, project settings, and render settings, Vegas is smart enough to do the resampling only once.

Now, if for some reason you produce an MPEG2 file that isn't the right format for the finished DVD then DVDA will re-render and this can produce another resampling if the aspect ratio of the MPEG2 file doesn't match the project you have set up in DVDA, so it's best to avoid this by making sure your render template in Vegas matches the DVD you want to author in DVDA.

So other than having to worry about the aspect ratio of the finished project, Vegas just does the "right thing" for you and minimizes the resampling to the absolute minimum.

However ... two other points to consider:

Lots of folks don't quite get it through their heads at first that the resolution of the finished DVD will be 720x480 (NTSC) or 720x576 (PAL). They'll use gloriously detailed 5MP images and wonder why they look so low resolution on the screen. You just ain't gonna get more than about 0.3MP in the finished version no matter what. Is it possible that this is the cause of the poor image quality you're seeing?

You mention Pan/Crop, and this is a good thing. However, should you be tempted to play around with Track Motion, keep in mind this is the one case where Vegas *DOES* add another resampling step. Any media affected with Track Motion is resampled to the project properties size first, then manipulated according to the Track Motion settings, then will get resampled again for preview/rendering. This means that Track Motion is the worst way to zoom in on an image.

Chienworks:
Hi and thanks for detailed response. Having experimented with a couple of DVDs,

the poor image quality is definitely down to being resampled twice. I wanted to

see if the extra resampling was noticably detrimental, and you can clearly see

that it is when resampling standard to widescreen in DVDA.
I understand and was aware of your point about DVDs being low-res by definition.

In fact, widescreen DVD images would actually be lower-res than standard, due to

the larger (wider) pixel dimensions.

The conclusion many DVD producers come to is to leave everything au naturel; start with a widescreen project, and include the 4:3 video segments at their native aspect, no cropping, no stretching, no magnification, and with unapologetic side pillars. Documentary editors who choose to do otherwise are uninformed and in the minority, IMO.

"when resampling standard to widescreen in DVDA"

Why would you do this? If you want a widescreen DVD, create a widescreen Vegas project and render a widescreen MPEG2 file for use in DVDA. That way you'll only get ONE resampling, when the MPEG2 file is rendered.