Conversion of old film

I have old film 35mm film footage that was converted to DVD about 15 years ago, and then I converted it to MP4. Quality is ok, considering some of the footage is 60 years old! Some of the frames I'm working on are interior shots that are very dark, and the few seconds of light shots are grainy and blurry. Is there any way to lighten the dark shots, and sharpen the blurry ones? I've applied various filters with little or not effect. Am I not digging deep enough into FCPX, or is it not possible due to the age and the fact that it's been converted a couple of times?

Hi KB, Welcome to the forums.
If you still have the actual film, you may be far better served to make a new digital copy from that. You will get far more resolution and will be able to do more with the new digital copy. Also the transfer processes now are much better for quality.
The condition of the original film will play a big part in details, overall dynamic range, etc….
I am afraid that the original transfer to DVD limits the resolution and your abilities to alter the stock. At least you didn't transfer to VHS first. Those really need new copies.
All digital transfers entail some "loss" but still old films are "Digitally Remastered" all the time.

As to working with what you have, You will really need to do extensive Color Corrections. FCPX may not provide the best tools and control for this. You might want to use a more powerful 3rd party color correcting tools. DaVinci Resolve (free) provides some very good tools including "Curves" and Color, Hue, Saturation levels beyond what you will get in FCPX. Unfortunately, I think the Noise reduction tool is the "Pro" Studio version only???

Work on small sections at a time. Use the scopes. Try to get the dynamic/exposure range first, then Color, then Saturation. Add in noise reduction / sharpen last. See if this works. I would do as much manually as possible. The automatic effects may not give you all you need for footage that needs surgery instead of just triage.
Then again, many modern clean shots have "Aged Film" effects applied to them, so you are just ahead there

Good Luck
Hope this helps, Greg

Yes, find a company that's been digitizing old film for a long time.
In FCPX, I'd use one of the third party color grading plugins, like Color Finale. That will do a lot to help out.
Noise, well, that's always been a tricky thing to work with. If there is too much, or it is too prominent, you won't kill it off much, even with DaVinci. Depends on what the source looks like.
I'd also agree to the suggestion to simply present it as archived film, let it look like it looks. Yes, get it as clean as you can, but, let it stand for what it is. Could lend some emotion and novelty to it.

the original 35mm contained about a billion times the image information that MPEG2 can deal with. Transcoding the old MEPG2 to MP4 further degraded the picture information but not much. There's not much you can do to this highly compressed image at this point. You cannot recover what's been thrown away—although you can simulate some of it—and you threw away a lot.

Converting 35m to HD is stupidly expensive but you are paying for an operator with specialized skills who uses really big and cool toys.

Depending on where you are, you might be able to rent a 35mm projector and just shoot your film off a screen to HD. That's how we're preserving miles of our corporate history that is on 16mm camera originals. It's not very pretty but when I gave management a quote from a reputable film transfer house they completely plotzed.

Thank you for the input. This project is actually one I'm doing for someone else, and the original isn't available. I've downloaded DaVinci and am doing a crash course on how to use it to see if it helps, but I'm afraid I'm out of luck. But everything y'all have told me has been extremely helpful!