beginner confused about lenses

captblue1 · Nov 2, 2005

I know this has been asked many times and i did do a search but i still don't understand. I am a beginner and have been hanging around for a couple of months now. my question is ::: how can i tell if one lense is better than another?
for example, which is better

35-80 f/4.0-5.6

or

35-80 f/3.5-5.6

I know what the 35-80 means. I just wanna know which one would give a sharper pic
thanks

DocFrankenstein · Nov 2, 2005

you can't, unless you look at the rating for that specific lens.

captblue1 · Nov 2, 2005

what do you mean rating. please elaborate.

DocFrankenstein · Nov 2, 2005

But wait... you can approximate quite nicely:
And the more expensive one will probably be sharper.

Also - both of the lenses you mentioned are probably going to be soft... since they're typical consumer lenses.

DocFrankenstein · Nov 2, 2005

You can look at MTF charts, which measure resolution.
You can look at "scores" on sites like www.photodo.com
You can ask around and read reviews. Usually every lens has a reputation of some sort... soft... slow focusing... sharp... good/bad build.

What's your camera brand?

captblue1 · Nov 2, 2005

so the f/3.5 doesn't necessarily mean it is better or worse than a f/4.0?
I have a Canon Rebel G2. i'm not looking to buy a new one. just wanted to learn about them.

woodsac · Nov 2, 2005

You can't tell which one will give you a sharper image just based on the aperture limits. Google aperture and understand how it works. Most lenses perform at their best (sharpest) when they are stopped down a couple stops from maximum.

If I had to blindly pick a lens on what you listed, I would go for the f/3.5, because it lets more light in. But it might take it's sharpest pictures at f/8. If you know what lens it is, you can read about it at fredmiranda.com. But...take the reviews with a grain of salt. Most of the reviewers (not all) have a habit of comparing every lens to that particular manufacturers top of the line lens. So, if you are not a professional, you don't need to spend $5000 on a lens to get *great quality* photos.

captblue1 · Nov 2, 2005

ok thanks

Meysha · Nov 2, 2005

the numbers 4.0 - 5.6 and 3.5 - 5.6 are describing the size of the aperture. Or how much light the camera can let in.

If you have a small number like 3.5 then that lets in a lot of light, 4.0 lets in slightly less light.

Now why are there two numbers on each lens?
Well when you have the lens zoomed all the way out at wide angle, in this case 35mm, then your biggest aperture will the 3.5 and 4.0 depending on the lens. But if you zoom it right in to 80 your biggest aperture will be a lot smaller at 5.6 on both lenses.

Hope that makes it a bit clearer as well.

danalec99 · Nov 2, 2005

captblue1 said:
i'm not looking to buy a new one. just wanted to learn about them.

This would be a nice place to start - FAQ; basic photgraphy concepts and vocabulary for newbies

captblue1 · Nov 3, 2005

thanks, i understand the basics, i just didn't know about the lenses.
i thought of something else to ask. are there any physical differences between $100 lense and a $3000 lense. is the glass a better quality? thicker or thinner. are other materials better. i guess what i am asking is what makes a $3000 lense a $3000 lense

Rob · Nov 3, 2005

Usually the cost of a product is a composite of the amount of R&D money it has taken, the number of years of production, the cost of materials and the features it offers to the consumer combined with healthy competition with rivals e.g. Canon vs Nikon.

There are $100 lenses which are fantastic. The obvious example is the 50mm f1.8 prime lens from any major manufacturer. All big brands have a "standard" prime lens which is the one that a lot of development has gone into. It's not complicated, doesn't have to do a load of different tricks and should provide a great sharp image from corner to corner.

Most of the big manufacturers will make a constant aperture mid-range telephoto zoom, like a 70-200 f2.8 with image stabilisation and other cleverness. This is going to be a fantastic sharp lens with great light potential at both ends of the zoom and a crisp and sharp image with no dodgy aberations. This will cost about $3000 as it's a *****-load of development to get a lens to work at both ends of the zoom properly. It's a nightmare to make with lots of moving glass elements which need to be huge to get that lovely f2.8 aperture at the long end. It's also got little whizzy silent motors in it which help you focus and relay information about distance, focus, etc. to the camera's body. This all costs.

However, most people won't spend $3000 on a lens, so they offer something which sounds great from a zoom point of view, but cuts corners and does not offer constant aperture, image stabilisation, or in some cases is just made of crap plastic. Hence there are consumer zooms which are typically f4+ and may range from very wide to very zoom i.e. 28-400mm f5.6 => f8. These lenses may work well for people for general photography and many will not need that extra light from the greater aperture or the whizzy electronics. However, it's probably not going to be as sharp, the focus may be slower or less accurate and there are a myriad of other reasons why people prefer "pro" zooms over "consumer".

Does that help?

Rob

woodsac · Nov 3, 2005

Remember the old saying "you get what you pay for"? Well if that holds true anywhere, it's when purchasing glass for your camera! The more expensive 'pro' glass has better everything.