Best way to rescale 4k images in HD project to preserve as much quality as possible
I am conforming a project edited in Avid, in Resolve. The project is HD, but there is a lot of 4K drone material in the project.
The drone material was rarely shot at a 16:9 ratio, and was usually wider, meaning letterboxing, (with the project settings input scaling set to scale entire image to fit). This is fine, because it is only a simple matter of resizing the images to fit a 16:9 frame and as its all shot at 4K anyway, the material will still all be HD quality.
However, I'm wondering whether or not I'm fighting with myself depending on settings. For example if the input scaling is set to scale entire image to fit, and that operation is performed first before the material is even in a timeline, does that mean that an increase in scale to crop out the letterboxing is essentially zooming in on something that is HD rather than 4K? As in, am I squashing the image down to HD and then blowing up that HD image? Thus resulting in a resolution less than HD by the end?
Also, where in the program is the best place to perform the scaling that is necessary to crop out letterboxing? I was thinking I'd like to do it in the node sizing tab so that the operation can be undone by simply enabling or disabling a node in a quick on/off fashion, but it's unclear to me if my above concern is indeed happening in this instance. One thing I read was that you can do it in the edit tab, under inspector, and changing the scaling parameter to crop. This is what I'm doing in the mean time until I can get an answer, because it leaves me relatively confident that it's overriding the input scaling (which is the type of scaling I want in most instances) and using the full available resolution of the image. It's just that it's more steps, per individual clip, and also makes the task of deciding what level of scaling to apply more confusing because it's a matter of zooming out by a certain measure, rather than zooming in and the extent to which I have to adjust that scaling is a greater amount than would be needed if zooming in. I need to keep zooming out until I see the letterboxes and know I've gone too far and then increase the zoom until I find the sweet spot. Just wonder if there's a more efficient means of doing this?
I deal with non 16:9 drone footage scaling on the edit page. I don't see any difference doing it there or in the color page. In the edit page however, you can do one clip then copy it and the paste scale attributes to all the other drone shots. Very quick and efficient way to do multiple clips at once and perhaps quicker than copy appending node in the color page. If you want to do it in the color page perhaps group all the drone shots and do the scaling to the group. this might be potentially more limiting as you may wish to tweak the vertical scaling on some clips differently to the others which is easier to do on the edit page.
As far as the HD timeline is concerned fit to fill then scaling is just working with 4k to HD no matter where you do it.
Ok, I guess you're probably right about bulk application of the change using paste attributes.
That's interesting what you say about it's ability to always be using the full available resolution of the 4K. It's good to hear someone sound confident that that is indeed what happens. I'm paranoid you see because Premiere Pro has a serious 'gotcha' problem with regard to resolution scaling whereby if you want the image to fit your frame there's two settings for achieving that aim with really vague names that seemingly do the same thing but one of which has bad consequences if you do any further scaling.
I know we're talking about Resolve, but there's a point for digressing in to Premiere. In Premiere, if you have a 4k image in an HD timeline, you'll find when you put the playhead over the image, that it's centre cropped, you're not seeing the full image, only 1920x1080 sized box within the centre of it. Now you can adjust the scale manually using the scale attribute, but if you want it just fill the frame, you can do it in a single click. One way of doing that is to choose an option called 'scale to frame size', which when clicked, resizes the image to fill your frame. However, there's a trick, because if you click that option, the 'scale' attribute remains unchanged, it stays at 100, and if you later decide that in fact you wanted to zoom in a little on something, and you scale to 130%, in fact you lose quality because when Premiere 'scaled to frame size' it actually resampled the clip and made it the same resolution as the timeline, therefore further scaling in is actually blowing up an HD sized shot, not a 4K one. But if you don't click scale to frame size and instead click 'set to frame size', the image is resized to fit your frame and the scale tab is adjusted accordingly and because the image is bigger than the timeline resolution, the scale parameter is set to a lower value in order to shrink the footage to fit and if you later decide you want to to be a little more zoomed in after all, you adjust the scale to a value that is less low, but not above 100. There's a similar issue in Avid too where any material that goes through it's 'import' process is resized to fit the project resolution and thus no longer 4k (there's caveats to this depending on some steps you can take but that's the standard behaviour).
That rant about Premiere and Avid had a point though because basically, if I'm adjusting the node sizing parameter, it's set to 1.000 by default and zooming in from there means a value above 1.000, but since scaling is applied as part of the input scaling settings set for the project, you can see why I might wonder whether it was pulling a Premiere on me. The same goes for scale parameter in the inspector, because if you have input scaling applied, and you have the 'resize filter' parameter set to project settings, then it too defaults to a zoom of 1.000 which again introduces the ambiguity (at least at a UI level) over what actually happens, this is why I was taking the extra precaution of setting each drone shot to the 'crop' resize filter.
How is it that you found out that it definitely doesn't 'pull a premiere' regarding scaling?