Go Back   Steve's Digicams Forums > Digicam Help > Newbie Help

Reply
 
Thread Tools Search this Thread
Old Sep 25, 2011, 2:29 AM   #1
Junior Member
 
Join Date: Sep 2011
Posts: 2
Default Nikon 24-70mm problems?

Hello everyone. My problem is with the 24-70mm 2.8 lens that is getting so many rave reviews... Here is my problem, When I got this lens yesterday I was very excited... I only have a D90 for now and from what I read it seemed best to invest in a great piece of glass for my future D700 body... After I put the lens on I was stunned that I could see no difference from my 18-105mm kit lens??? I performed test after test after test, all types of metering, FL, focus points... There is not a increase in performance... Is this common? do I have a bad lens? or does this lens need to be on an FX body to really shine? Are there any steps I can take to make sure it is NOT the lens? I purchased it brand new from B and H.
shadowct is offline   Reply With Quote
Sponsored Links
Old Sep 25, 2011, 11:11 AM   #2
Administrator
 
Join Date: Jun 2003
Location: Savannah, GA (USA)
Posts: 22,378
Default

If you're not seeing any difference in image quality at settings in common with them, it's probably working just fine. ;-)

Your 18-105mm is a relatively sharp lens, even at wide open apertures. Click on the blur chart in this review, and you can use the sliders to change focal lengths and aperture and see a nice chart showing lens performance:

http://www.slrgear.com/reviews/showp...ct/1221/cat/13

Here's a review of the Nikkor 24-70mm f/2.8 AF-S lens there that you can do the same thing with:

http://www.slrgear.com/reviews/showp...ct/1121/cat/13

If you look at areas like distortion and vignetting, you may see some difference, depending on focal length. But, the 18-105mm has wider zoom settings, where you'd expect to see a bit more barrel distortion and vignetting. At focal lengths in common, I doubt there's much difference, as that kind of thing drops off by the time you zoom into around 24mm with the 18-105mm.

Bokeh (the quality of the background blur) is probably better with the newer 24-70mm in some conditions. But, you can't expect to buy a new lens like that and see photos magically improve at focal lengths and apertures in common, if you're already using a pretty decent lens.

You've got f/2.8 with the new Nikkor. So, it's a much brighter lens. By the time you zoom into around 35mm with the 18-105mm, it's widest available aperture is already down to f/4.5 (so the 24-70mm f/2.8 is more than twice as bright at the same focal length).

By the time you zoom into around 70mm with the 18-105mm (the long end of the 24-70mm), the 18-105mm only has a widest available aperture of f/5.3 (so the 24-70mmm is almost 4 times as bright as your kit lens at 70mm).

Your kit lens is an f/3.5-5.6 lens, meaning that it's widest available aperture is f/3.5 at it's wide angle zoom setting, dropping off to a widest available aperture of only f/5.6 at it's longest zoom setting. f/5.6 is a relatively dim aperture if you need faster shutter speeds in borderline lighting. f/2.8 (which your Nikkor 24-70mm f/2.8 has available throughout it's focal range) is exactly 4 times as bright as f/5.6, allowing shutter speeds 4 times as fast for the same lighting and ISO speed.

Another benefit of a brighter lens is that your AF sensors can "see" better. So, in dimmer lighting, a brighter lens like that Nikkor 24-70mm f/2.8 can really help with AF performance.

Light is typically measured as EV for Exposure Value in Photography.

Aperture (which works similar to the pupils in your eyes, where you can open up the aperture iris wider to let in more light, or close it down to let in less light). If you let in more light with a wider aperture, you can expose the film or sensor faster. If you let in less light with a smaller opening, it takes longer to expose the film or sensor. Note that aperture is normally expressed as f/stop, which is a ratio between the focal length of the lens and the diameter of the aperture iris. So, smaller values represent a larger iris diameter.

With a prime (non zoom) lens, you will see one aperture listed (the widest available). But, you can still use smaller apertures (represented by higher f/stop numbers).

With a zoom lens, you usually see two apertures listed (the largest available aperture at wide angle zoom setting, and the largest available aperture at the full telephoto zoom position). When in between the widest and longest focal length of the lens, the largest available aperture will fall somewhere in between the apertures shown.

Many high quality zoom lenses like that Nikkor 24-70mm f/2.8 can maintain a constant aperture throughout their zoom range (with f/2.8 being the most common). So, you'll only see one aperture listed for this type of lens (the widest available, since you have that aperture available at all focal lengths supported if desired). But, you can still set it to smaller apertures (higher f/stop numbers). For lower light, primes (fixed focal length versus zooms) can be found that are brighter (smaller f/stop numbers).

When you vary the aperture, you're controlling the iris in the lens (which like a pupil in your eye, can be opened up to let in more light or closed down to let less light in). So, this impacts the shutter speeds you'll need for proper exposure (since more or less light is getting through to the sensor). Aperture also impacts Depth of Field.

The aperture scale in one stop increments (with larger than f/1 apertures possible but very rare in lenses) goes f/1.0, f/1.4, f/2.0, f/2.8, f/4.0, f/5.6, f/8.0, f/11, f/16, f/22... With each one stop move to a smaller aperture (represented by higher f/stop numbers), you will need shutter speeds twice as long for proper exposure for the same lighting and ISO speed (only half the light gets through compared to a one stop larger aperture).

ISO speed is how sensitive the film or sensor is to light and is the same thing as the older ASA rating for film. The higher the ISO speed, the faster you can expose it (each time you double the ISO speed, you can use shutter speeds twice as fast for the same lighting and aperture.

Shutter Speed is how long the camera's shutter stays open to expose the film or sensor).

IOW, it all boils down to how sensitive the film or sensor is to light (which you control via the ISO or ASA speed of the film you use with film, or the ISO speed settings you use with digital), and how much light you need to let it see to "expose" the iimage (which you control via the aperture opening size and shutter speed).

http://www.photonhead.com/simcam/shutteraperture.php

Note that aperture also influences depth of field. See this handy calculator for more information about it:

http://www.dofmaster.com/dofjs.html

Bottom line:

The Nikkor 24-70mm f/2.8 AF-S is an exceptionally sharp lens for a wide aperture lens capable of f/2.8 throughout it's focal range. It's a much brighter lens compared to your 18-105mm f/3.5-5.6 kit lens, and you won't do any better if you want/need that type of lens for use on a Nikon camera model.
JimC is offline   Reply With Quote
Old Sep 25, 2011, 11:12 AM   #3
Administrator
 
Join Date: Jun 2003
Location: Savannah, GA (USA)
Posts: 22,378
Default

BTW, I see this is your first post here.

So, Welcome to Steve's
JimC is offline   Reply With Quote
Old Sep 25, 2011, 4:46 PM   #4
Junior Member
 
Join Date: Sep 2011
Posts: 2
Default

Wow... Thank you! I guess for the price of these suckers I was expecting some pixie dust magic with it. I fully understand the increase of lighting performance, But in a lot of cases my little kit lens is 9 out of 10 shots dead sharp, I am sure VR helps a ton with this. I guess some serious practice is in order to get this new lens steady. Thank you so much for you help!
shadowct is offline   Reply With Quote
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 8:05 PM.