I'm confused about something ... f/2.8 lenses

[Leftyplayer]

My experience with the limited zoom lenses that I have is that for example, if I'm at 18mm, I can access 3.5 aperture, but once I start zooming out, say, to 75mm, I no longer have access to 3.5 - I only open as wide as 4.5 or 5.6 (these are just examples). However, as I'm looking into upgrading my whole system, I'm looking at lenses, like 24-70mm f/2.8 or 15-85mm f/2.8 and reading comments like, "it's great to have access to 2.8 all through the zoom range." Does that mean that even at, say 85mm, the lense can access 2.8 aperture? Obviously, you may not WANT to, but can you. I didn't think zoom lenses can do that, which is what makes primes so special -- you get to have 105mm at 2.8 (or whatever).

Am I misunderstanding what I'm reading?

(p.s. I'll start another thread for help deciding on my new gear -- look out for it :mrgreen

Here's one of the quotes that led me to wonder ... "I have Sigma 2.8 70-200. Its a monster lens, but I wanted 2.8 across the zoom in addition to a good zoom in general."

 

[Kerbouchard]

Nope, that's pretty much it. Most professional lenses don't have a variable aperture based on focal length. You have a max aperture of 2.8 throughout the zoom range.

There are also some Canon and Nikon lenses that are a bit cheaper than the 2.8's and they are f/4 throughout their range.

 

[D-B-J]

Correct. A constant aperture of 2.8 is maintained throughout the zoom range. Why do you think the 70-200 2.8 VR II is so much more expensive than the 70-300 VR 3.5-5.6? To maintain this consistent wide aperture, the lenses require significantly more glass, making the heavier and more expensive. But yes, some zooms can, and the 2.8 aperture is there at every focal length.

Regards,
Jake

 

[480sparky44 44]

Many zooms are variable-max. aperture. Once you set it for the smallest, it will remain the same throughout the zoom range.

For instance, if you have an f/3.5-4.5 zoom, and open it up all the way, it will be a f/3.5 at one end of the zoom range, but f/4.5 at the other end. If you set the aperture to, say, f/5.6, it will be f/5.6 no matter where you set the zoom.

 

[Tomasko]

If it says f/2.8, it's f/2.8... If there's no range written like 3.5-4.5, but only one number, it means, that you can use such aperture throughout whole zoom range. That's why these lenses are quite expensive

edit: eh, I'm too slow I guess

 

[table1349]

My experience with the limited zoom lenses that I have is that for example, if I'm at 18mm, I can access 3.5 aperture, but once I start zooming out, say, to 75mm, I no longer have access to 3.5 - I only open as wide as 4.5 or 5.6 (these are just examples). However, as I'm looking into upgrading my whole system, I'm looking at lenses, like 24-70mm f/2.8 or 15-85mm f/2.8 and reading comments like, "it's great to have access to 2.8 all through the zoom range." Does that mean that even at, say 85mm, the lense can access 2.8 aperture? Obviously, you may not WANT to, but can you. I didn't think zoom lenses can do that, which is what makes primes so special -- you get to have 105mm at 2.8 (or whatever).

Am I misunderstanding what I'm reading?

(p.s. I'll start another thread for help deciding on my new gear -- look out for it :mrgreen

And now you know one of the reasons for the big price difference. You get what ya pay for.
Canon EF-S 18-135mm f/3.5-5.6 = $329.00
Canon EF 24-70mm f2.8 = $1,349.00

 

[Leftyplayer]

Holy cow!! I didn't know! That is the BEST thing I've heard in a long time.

It wouldn't have mattered when I wasn't ready, but I've now paid some dues with my little Rebel XS and kit lenses - out there shooting constantly, taking workshops and lessons, reading everything out there to learn from and taking feedback with my head down. I've outgrown my current setup and will be moving up to the 60D (still wavering with the 7D as a possibility as well) and two new quality lenses, 70-200mm f2.8 ... and deciding which other lense at the other end, but probably 24-70mm.

 

[flea77]

While the fixed aperture certainly is a plus on primes that is not really a reason to prefer primes over zooms. Some reasons include:

1) Generally, primes are sharper and give an all around better image
2) Generally, primes can be faster (50mm f1.4 vs 24-70 2.8 is a HUGE difference)
3) Generally, primes are smaller, lighter and focus faster
4) Generally, primes are less expensive but rely on your sneakers to zoom back and forth

Now there are exceptions to almost every rule and some of the differences may be too small for you to care, but there they are.

Allan

 

[Leftyplayer]

Thanks, Allan, for the info. The two lenses I'm considering getting first are zooms, but I'm sure I'll eventually take a closer look at the primes. I currently have the 50mm 1.8 and enjoy it, and know I'll grab the 135mm at some point as I do find the 50mm a bit too close for comfort in some situations. I've also got some interest in a macro - but don't fully understand those yet and will do the homework when the time comes. For now, just new body and two fast zooms : )

 

[Patrice]

Holy cow!! I didn't know! That is the BEST thing I've heard in a long time.



I currently have the 50mm 1.8 and enjoy it, and know I'll grab the 135mm at some point as I do find the 50mm a bit too close for comfort in some situations.

I think you might have a bit of reading and catching up to do.

Constant aperture zooms have been around for a while now.


If you find a 50 mm lens a bit too close, the 135 mm is not going to be much help. It's field of view is smaller than the 50 mm. Unless you mean that you have to be too close to the subject to get the view you want.

 

[Leftyplayer]

I think you might have a bit of reading and catching up to do.

No worries, I'm still very aware of being a newb - the learning continues, always. In my defense, I should say that I have focused my learning on improving the craft with full acceptance of the gear I started out with, so I haven't really looked much into the gear that's out there (or how it works) until recently. There was no point until I knew the very basics of photography - interplay between aperture, shutter speed and ISO, white balance, good composition, correct exposure and more creative exposures, lighting, etc etc. Still much to learn and definitely a lot to learn about all the gear that's out there! So exciting.

Unless you mean that you have to be too close to the subject to get the view you want.

Yes, I mean too close to the subject.

 

[shaunly]

Another reason why f/2.8 lens are so much more expensive is because pretty much all of them are "pro" graded. Which means much better construction, better AF, more exotic glass for better IQ and sometimes more features.

 

[Village Idiot]

Another reason why f/2.8 lens are so much more expensive is because pretty much all of them are "pro" graded. Which means much better construction, better AF, more exotic glass for better IQ and sometimes more features.

Plus they take more glass. A 16-35 f/2.8 or 17-40 f/4 vs a 10-20 Canon or 10-22 sigma with a variable aperture is going to be a bigger, heavier lens. Ever hold a Canon 85 f/1.2 or equivalent lens? That lens on a rebel body make the rebel body look like an Olympus DSLR.