|ScanCalc is a little helper to calculate image scan resolutions when working with video.
Many people aren't that sure about: What dpi should my still image have if I want work with it in my video sequence or composition.
Though the answer is somehow simple, it seems difficult to bring together the world of scanners or PhotoShop and the world of video.
Video normally doesn't care about dpi, only about effective size. So an HD frame could be 1920x1080 square pixels effective size, independent from the dpi setting used when scanning or creating the still. But with scanning it sometimes is a little bit difficult to get this dimensions. That's where ScanCalc can help.
The below is not a recommended use of this small application - it's just a quick guide thru the app's options, when you use it first time.
So assuming we would want to add some still to our HD sequence, we select the HD 1920 x 1080 from the format popup.
ScanCalc now will calculate the needed size in (square) pixels and will give you the needed size of an image (at the given aspect ratio) for a 300 dpi scan resolution. The 300 dpi is just a default setting, since virtually any scanner will support that resolution.
Now you got base the values (or an idea about) for that what you need.
This in many cases this is not that helpful, since you may want to zoom in or pan around. So you can use the "Zoom" slider to recalculate the needed image dimensions. Doing that also the actual file size will be re-calculated.
The result maybe still frustrating in some cases, since your artwork wouldn't match those sizes. So you can do some of your own settings:
Above I entered an A3 size for the width of my template (you can enter the height as well - though only one of the entered values will taken into account - or enter any inch value). The the values will be re-calculated, based on the width and the zoom factor. The new values also show that the height will be cropped - A3 = 42 cm x 29.7 cm.
Additionally a new dpi value shows up, which is some kind of best match. Looking at the other numbers, we see that this is not a perfect match, especially because many scanners wouldn't support 348 dpi natively. So we will lock our template size and enter one of the resolutions the scanner supports:
Again the values are re-calculated. But all input settings kept their values, only the "Info" will be updated, so we see that with this settings our file (size) will grow and we got the scale down factor we need to match and the maximum zoom we can achieve, if we don't scale down.
Scaling down normally is a good option, since down-sampling improves image quality in most cases, especially if you got horizontal lines or print stuff, which may flicker in video when scanned at a 1:1 setting.
With the above we might have got an optimal setting for our given template, but that doesn't mean it will work in any case. Final Cut Pro for example only supports file dimension of 4000 pixels in any of the x/y directions.
If we need to work with the above video (or film) format and the selected zoom factor, we could for example use After Effects to create the motion (40.000 px limit) or scan/save the image in two (or more) versions and blend them over time in Final Cut Pro.
As said above this not a recommend way to use the app - just a small tour. You may start with a given template size, lock it then select the video/film output format, zoom and fine tune the scan dpi, you may also may start with a given video/film format and play around with the dpi settings to get an idea of the template you need .