If I remember my lessons correct, white debris like that was dirt on the negative, so in theory yeah wet baths are supposed to get rid of things like that but if its something super grungy on the film might not have been caught.
Hold on, wet gates surely just do one thing. They fill in base side scratches on the film by using a liquid with the same refractive index as the film base. They don't clean film. A white spot is sparkle - something dark on the negative. Depending on what it is, an ultrasonic cleaner might get it off. But it might not if it is stuck on the emulsion side.
As others have mentioned, wet gate is only useful if you're dealing with base scratches *and* the scanner uses a collimated light source. Modern scanners with diffuse LED light sources perform the same function as a wet gate, because the light is bouncing all over the place and doesn't refract in base scratches in the same way a focused light source would. What kind of scanner was used, just out of curiosity?
Are you scanning original negatives, or an intermediate? If it's an intermediate, it's possible the dust was on the original neg, and then transferred to the intermediate. Thus, it's baked in and is part of the picture now. No amount of cleaning would take that off. If it's the original neg and an ultrasonic cleaning didn't get it, then digital is the way to go. PFClean will do it, but it's a bit of a nightmare to work with, and is pretty crash prone. If you only have a few spots here and there, you might be able to do it in Resolve, using the built-in dustbusting tools. All manual, but they do work. I wouldn't do a super dusty film that way, but it's free, and the only caveat is that you need to be working from a DPX sequence to use those tools. It won't work on Quicktime files or other containerized media.
Regarding the question about Overscanning - that's more of a personal preference thing. If you're using a pin-registered (optically or mechanically) scanner, you're going to get a very stable image. If you're not, the film may bob or weave a bit in the gate. If you want to stabilize it, having the frame lines and perfs visible can help you to do that in post, by giving you a consistent reference point. One thing to bear in mind with overscanning, though, is that if you get a 2k scan that's overscanned, you should ask the lab to make sure they give you a slightly bigger scan, so that your frame area is still 2k. If not, it'll be slightly smaller. In most cases this doesn't really matter much, but if you need to have 2k or 4k, you will probably want to scan at 2.3k or 4.3k, respectively (or something around that size, depending on the amount of overscan you want).
I did the scan as flat/raw. Is PFClean ok for flat/raw type of scan?
We don't do restoration on the flat files - if you do, then when you color correct you might expose defects in the restoration fixes that weren't visible in the flat scan. Restoration should come last, after you've finalized all your color correction.
You *can* do it, but you'll probably have to go back after grading to re-do stuff, so I don't recommend it.
With PFClean, you take a sample of previous and next frame, just large enough to cover the defect. The program will motion interpolate if possible, in case of very rapid movement between frames, it can be set to only take local pixels from current frame. You can also make it interpolate for flicker if present; we always dustbust before colorgrading. There also is an automatic mode that works well if the shot is fairly static. We prefer the manual mode. I think you can get a 30 days trial version. It is a very deep program and will require many years of practice to master most of it. On the other hand, the dustbusting is fairly straightforward and you can see the result immediately. You can render to a different directory so you don't overwrite your original files if you are not sure of your skills.
I think photoshop also has a similar but less powerful tool, if only for a few dozen frames, it might work.
The scanned film is FF 35MM Color I/N "B" Wind 1 Roll. That's what the scanning lab indicated. I am
not sure what "FF", "B" , "Wind" means.
FF = Full Frame (as in, not matted to a widescreen projection aspect ratio; very common)
I/N probably means Internegative.
A and B Wind refers to the orientation of the emulsion
I do understand that the wet-gate deal with scratches. I am just wondering why the leader with the count down 8,7,6, etc still shows scratches? I don't need that
part of the footage, but I was just wondering how come the wet-gate didn't do anything to that?
Leader shouldn't be what you're looking at. It's often re-used and reprinted by the lab and is rarely as clean as the film itself. Dust and scratches are baked into subsequent printings of standard leaders, kind of like multi-generation photocopies. no cleaning or wet gate will deal with that, because they're printed-in scratches, not actual scratches in the film.
That said, wet gate is not a panacea. It's good for some things in specific situations, as described above. But it won't deal with very deep scratches. it primarily does its thing on light scratches, and only on the base side of the film.
The scanner used is spirit 4k with wet-gate. I didn't choose to do overscan. I had the lab scan to "Framed To Image" for 4K scan. I did notice that I lost
just a little bit of the right side of the image. Is this normal? Or could the lab do more to the scanning area for the 4K or 4.3K without capture the rails?
I don't know how wide the Spirit can go, maybe Rob Houllahan does (he's got one)?
With many modern scanners, the camera/film positioning can be varied. Older units had fixed camera positions, like our Northlight. So the framing is what it is (you can only widen it by physically widening the gate, which means machining it to be larger, and even then, there are limits. On a scanner like our Lasergraphics, the scanner is always scanning the film pretty much from edge to edge, and then cropping/scaling downwards. So you can do a very large overscan, or a small one, depending on what the job requires.