Topic: Difference due to quality?

Let's suppose I have a good camera body.
Then, let's suppose I have a regular zoom lens, and I take a picture with it, focal length set to 35mm, aperture around 5.6, speed at 1/60. (it was a cloudy day :-)
Then, let's suppose I have a fixed lens, that has a (fixed) focal length of 35 mm and a fixed aperture of 2.0 (that's a better quality lens).
I take the same picture as the first one but now, because the aperture is bigger (2.0 compared to 5.6), I compensate it with a higher speed.
Theoretically, both photos had the same amount of light.

My question is: how much difference will it make in the quality of the final picture, the quality of the image? Is there some site that has pictures showing the same shots taken with regular, cheap lenses and with more expensive pro ones, so I can decide if it's worth spending money to buy better lenses?


Edit: found this link http://www.aeimages.com/learn/lens-quality.html

[This message has been edited by viol (edited 03-09-2004).]

not sure about websites, but I know that when it comes to film cameras, theres only 2 parameters that define quality of the produced image: film itself, and lens. If you can afford better lenses you shouldnt think twice and get em.

oddly enough, it might turn out to be a draw in the situation you describe. Lenses don't perform at their best at wide apertures. All other things being equal, the f5.6 lens at 5.6 might be "sharper" that the f2 lens at 2. And there's a fair chance they would be a dead match at f8.

But there's a shutter speed issue that complicates things. A speed of 250 is likely to be sharper than a speed of 60 (assuming you are hand holding it). The faster lens used to be an advantage back when humans focussed cameras. It was nice to have that f2 if you needed it for low light, but it was even nicer all around to have the viewfinder 2 stops brighter.

There might be other factors here, such as design and construction, but if you don't typically find yourself pushing the envelop in low light situations with the lens wide open all the time, the money the faster lens costs might be a luxury rather than a necessity. In the early days of zoom lenses it was felt that fixed focal length design was superior to zooms and the compromises involved in designing them. I dodn't know if advanced design has narrowed that gap or people figured zooms were worth the penalty. In any case, comparing a 5.6 zoom with a 2.0 fixed focal length is a little hard to do fairly.



[This message has been edited by Steve (edited 03-09-2004).]

I made that comparison because I have these two zoom lenses but they are consumer level (one is the one that came with the camera, the Canon Rebel Digital). And the one I'm looking for is a fixed 35mm lens.

People keep telling that lens is an important element of the final quality of the picture and then, I was looking for some good quality lens and, obviously, they are all too expensive, I can't afford them.

A little more research and I found a Canon lens, the EF 35 mm f/2, no USM, absolutely no fancy feature but, according to all the reviews I read, its optics is superb for the price, around $230. Well, I can afford to spend this amount for a good quality lens and according to those reviews, and they are a lot, this lens is supposed to give results almost as good as its equivalent "L" series sister. But the "L" series equivalent lens is one thousand dollars more expensive.

So I thought: is it worth spending these 200 bucks? It's a fixed lens, 35mm is the equivalent to 55mm in my camera, this is one of the most used focal lens for me, so I am thinking on giving it a shot. It has no USM, almost all reviews agree that its biggest and probably only weakness is that its AF capability is noisy. Well, I don't mind the noise if I can get good optics, for the sake of learning how much of a difference better optics can do (well, as much better optics as my budget can afford). Besides, there is always the manual focus option.

I've taken some pictures with my current two zoom lens, and both indeed seem to suffer from that problem as described in the link above: far away trees that are supposed to be green look rather dark. I am able to correct the problem using Photoshop, but I wonder how much better the picture would be if I had used a better lens.

"far away trees that are supposed to be green look rather dark"
Doesn't sound like an optical flaw. One safety net might be to rent the lens - living where you do, Id suggest calling Calumet in Cambridge and seeing if they have that lens for rent. They are good people to deal with and have a pretty extensive rental department, so they might have that lens available. Could save you $230 of disappointment, could confirm it's just what you need.