Quote: try as i do to get a photo straight in the viewfinder, when i look at it later , it's hardly ever straight the same as i had it , not so much curved as tipped one way or other,
If you mean what I think you do, that's still one of my biggest problems. Take a landscape I think is straight, look later and find out it's tilted 5° one way or the other so the horizon slopes off to the bottom corner. Only cure for that is practice, and I suppose I'll never get enough practice, I still do it after 30 years...The only way I can get a landscape straight is to use a tripod.
For nature shots, birds, insects and such it's usually not such a problem, often you can't tell it but with things like a duck swimming around, it's not hard to see. And I can't use a tripod for that kind of thing.
Fortunately even the simple photo editing software I use, Irfan View, has a correction for that. I can set it at any angle I want, including parts of a degree by simply making it a decimal. So if I need to tilt it 3.6 ° it's no problem and as if by magic it's a straight picture. Then I have to crop it because the entire picture is cockeyed.
If that's what you're having trouble with, the only cure I know of is practice. And like I said, after 30 years I still do it regularly.