Body material - in the days of old they could do rugged things...

"Entry level". People are concerned about weight, and plastic is lighter than metal. The plastic isn't that weak- it's actually a pretty strong plastic. People who don't mind the weight and want super ruggedness can get a Nikon D300 or D3 :P.
Or go buy a film camera.

So why aren't all entry-level SLR cameras made of metal? I am engineer and do undderstand what manufacture cost mean... but aren't they aimed to seasoned photographers?

in a word, no. this may seem obvious but entry-level cameras are aimed at entry-level users. for "seasoned photographers" used to 35mm film focal lengths, there's the D700 and D3. in other words, you pay more for the benefit of experience. or metal DSLR bodies.

I'm not particularly nice to my cameras - they hang over my shoulder all day, and get a punch from time to time. I have not had any problems with the D70-body not being of metal. My experience is that Nikon cameras are tough.

Yes, see how many people are still using D50s. That means something...

Entry-level/consumer DSLRs are not aimed at seasoned photographers. They're aimed at as many people as possible. I think (but no source to back it up) that the majority of D40/D60/D5000 buyers will want the camera to take good photos of family trips and holidays. Exactly the occassions where a heavy bag with a rugged DSLR gets in the way....

And my D50 and D80 never felt like they would fall apart. Not a squeak, no play in the body panels, not after a lot of use either. Plastic as a material has come of age, and there is no longer need to do everything in metal, without sacrificing reliability.

But funny, nearly all engineers I know always tend to be a tad conservative when it comes to material choice. Old habits die hard, I guess ;-)

What a lot of people dont think about is the fitness for purpose of an object.

Entry level cameras are made the way they are because they fit the purpose for which they are intended.

People who need a ruged camera will have the money to spend on a better made body.

Also, modern plastics are very tough and stiff. Something which I would imagine is very important in a camera. Steel bodies will be prone to flex and warp.

What I would like to see however is a CFRP body, and see what fool would spend good money on it!

Just to add to Wouter's commend regarding engineers...

I am doing a PhD in aerospace materials and when I talk to more experienced engineers they always want to use what they used when they were "growing up".

I cant remeber the exact quote but I think its along the lines...

physics only changes when a physicist dies.

r

I was in the photo industry in the 1970s when plastic-body 35mm SLRs were first introduced. The roar of protest from experienced photographers was deafening. But consumers flocked to the new cameras in the millions. The new designs did exactly what the manufacturers intended -- converted non-35mm snapshooters to the world of SLR photography. The experienced photographers never did stop complaining; all the while a whole new mass market was being created around them. By the way, that's the same plastic that football helmets are made of. Engineers take note: Even better composite materials are now coming out of the aerospace industry.

Will

metal dents.

plastic bounces... to a point...

plastic is probably the best material for my D50. I wouldn't like it a lot heavier than this.