Explain to me F/2.8???

[93octane]

Explain to me how an arpeture of 2.8 becomes usefull???
I know:
allows more light in so you dont' have to use such a high ISO
Using it out doors a more/better arpeture is common 5.6 and above because of DOF more things can be infcous.
If using a 2.8 the DOF is sometimes very narrow so you can't use it so a larger arpeture is used.
Indoors is great because it lets more light in but if a narrow DOF is created why use it if you are still going to have to bump up the arpeture to 5.6 and use a flash to get a better DOF. In that case a 4/5.6 lens is better since you can be limited of the use of the 2.8 because of its narrow DOF this includes the 1.8 and 1.4 lenses??? Can someone explain when this arpeture becomes usefull?? I'm new to this only a year so bear with me..

[raylks]

You speak the point already. It is useful because it is fast!
You are shooting sports indoor and you want to freeze the movement of the athletics. The only thing you can do is to 1) push up ISO at the expense of grain; or 2) use large aperture lens. That's why f2.8 and faster lenses come into play.
About the narrow DOF problem. True. f2.9 has narrow DOF compared to other slower lens or slower aperture setting. But unless you are shooting the subject very closely, the DOF at f2.8 is still acceptable when you focus right at some reasonable distance because the focusing distance can compensate for shallow DOF.
Remember that DOF increasing with distance between the lens and the subject in focus. So when you are shooting sports, or other topics at reasonable working distance, your DOF at f2.8 is still giving you acceptably deep DOF.

[lostdoggy]

One word Bokeh.
The ability to blurr unwanted background and sometime foreground.

[schmoelzel]

Do you like portrait shots where the subject appears to jump out of a blurred background? That's a good reason to like a large aperture lens. If you shoot landscapes, you probably do not need an f1.4 lens. But if you like to shoot people (portraits), nothing looks better than a blurred backgound and a tack sharp subject. Yes DOF is narrow but that is where practice comes into play. The pros know how to focus properly and know how to press the shutter at the exact perfect moment to capture the shot. Here's a shot I took with my 50F1.4 at F2.......I was able to focus on her eyes but because I had opened the aperture a little more, it appears as if the rest of her is sharp as well. When you print this it looks great; when you look at it on the computer at 100% size you will see that her eyes and everything on that narrow plane is in focus but parts of her shirt and head are soft. That's normal for portraiture......none of us ever would notice such a thing in your typical 4 X 6 or even 8 X 10 print.

http://theteahaus.netfirms.com/Canon/nfpicturepro/albums/userpics/10001/50f1.4-1D-B.jpg

[steven]

There is also the point that no lens is at it's best wide open.
So for the F2.8 lens if you stop down to 4/5.6 you are no longer wide open.
But with a F4/5.6 you are wide open and not at the lens's best.

[jfrancho]

Having a large aperture aids autofocus in low light, since the lens only stops down for the brief instant the exposure is recorded.

[ayotnoms]

What is often left off of threads dealing with aperture is the crucial role that distance plays.

If I'm taking a photo of a person a short distance away with an f/2.8 setting, I run the risk of having a leading facial feature (eyes, nose, what-have-you) in sharp focus and a feature behind the focus plane (ears, for instance) out of focus. This, I believe, contributes to many-- often times-- erroneous conclusions that something is wrong with the lens.

If on the other hand, I'm taking the photograph from across a large room--again with the same f/2.8 aperture--that person's entire body can pop-out in sharp focus and with that pleasing 3D effect that we find so appealing with photography.

Check out this link for a better understanding of DoF.
http://www.dofmaster.com/dofjs.html

Also, here are 2 screen shots from the online DoF calculator highlighting the DoF so you can see the effect of distance on what's in focus and what's not in focus. DoF at 10 feet is very small but from a distance of 100 feet, the DoF is large enough to accommodate a group of people.

...if that's what you're photographing of course. :-)

Bottom-line, resist the temptation to look at the f/2.8 aperture and cast it aside as a feature for which you'll never find a good, effective, or creative use.

Cheers and apologies for the rambling post.

[CyberDyneSystems]

Taken at f/2.8

http://carmenpremier.fotopic.net/p5023608.html

[ayotnoms]

Taken at f/2.8

Too bad that lens works so poorly wide open. You should send the lens back cause it's obviously defective.
:p

Seriously, this photo is the perfect example of how to properly use a well-crafted piece of glass wide-open.

:lol::lol:

[jfrancho]

What is often left off of threads dealing with aperture is the crucial role that distance plays.

If I'm taking a photo of a person a short distance away with an f/2.8 setting, I run the risk of having a leading facial feature (eyes, nose, what-have-you) in sharp focus and a feature behind the focus plane (ears, for instance) out of focus. This, I believe, contributes to many-- often times-- erroneous conclusions that something is wrong with the lens.

If on the other hand, I'm taking the photograph from across a large room--again with the same f/2.8 aperture--that person's entire body can pop-out in sharp focus and with that pleasing 3D effect that we find so appealing with photography.

Check out this link for a better understanding of DoF.
http://www.dofmaster.com/dofjs.html

Also, here are 2 screen shots from the online DoF calculator highlighting the DoF so you can see the effect of distance on what's in focus and what's not in focus. DoF at 10 feet is very small but from a distance of 100 feet, the DoF is large enough to accommodate a group of people.

...if that's what you're photographing of course. :)

Bottom-line, resist the temptation to look at the f/2.8 aperture and cast it aside as a feature for which you'll never find a good, effective, or creative use.

Cheers and apologies for the rambling post.I'm glad you brought this up. It seems like every other post I'm pasting a link to DOFMaster. Once you understand how the "trinity" works - Aperture, shutter speed, and ISO - this is the next crucial bit that I think many forget. You may think you know how you are influencing DOF with your settings, but it is a revelation to see the math at work. Many myths have been dispelled with the DOF Calculator, and my photography has improved greatly since using it.

[condyk]

Taken at f/2.8

http://carmenpremier.fotopic.net/p5023608.html

I thought only Superman wore his undies outside his pants :lol: :lol:





Note: this weak humour may lose something in transatlantic translation.

[ayotnoms]

I'm glad you brought this up. It seems like every other post I'm pasting a link to DOFMaster. Once you understand how the "trinity" works - Aperture, shutter speed, and ISO - this is the next crucial bit that I think many forget. You may think you know how you are influencing DOF with your settings, but it is a revelation to see the math at work. Many myths have been dispelled with the DOF Calculator, and my photography has improved greatly since using it.

Yup.
I've had many a V-8 moment since educating myself on the "Trinity" (nice turn of the phrase BTW. I think I'll steal it ;-))and the output, as you say, has improved immensely.

[blue_max]

Note: this weak humour may lose something in transatlantic translation.


It lost quite a lot travelling across a few counties!
:lol:

Graham

[93octane]

Ok I think it all makes sense now. The key to not letting your DOF effect your picture in a bad way is distance from your subject.

[jfrancho]

Yup.
I've had many a V-8 moment since educating myself on the "Trinity" (nice turn of the phrase BTW. I think I'll steal it ;-))and the output, as you say, has improved immensely.Go ahead and use it, royalties are to be paid in L glass.

[jfrancho]

Ok I think it all makes sense now. The key to not letting your DOF effect your picture in a bad way is distance from your subject.Its not that it will be "bad", just unexpected. And it is distance from your subject, focal length, and COC (I won't get in to that here, just use the default value given for your camera model) along with aperture that influence depth of field.

[Andrew Pratt]

Thanks for that DoF calculator. It helps explain a great deal about what I've been seeing with my new 70-200L f/4 with so much of the image being out of focus...no wonder when you use the lens to shoot objects that are less then 20 feet away with anything less then f16!

[ayotnoms]

Thanks for that DoF calculator. It helps explain a great deal about what I've been seeing with my new 70-200L f/4 with so much of the image being out of focus...no wonder when you use the lens to shoot objects that are less then 20 feet away with anything less then f16!
The light bulb was there over your head the whole time.
...just needed a nudge (and a link) to yank on the string. LOL

Now you're going to see what that sweet 70-200 L-glass can really do!

[ayotnoms]

Go ahead and use it, royalties are to be paid in L glass.
Good lord, man.

Besides my expensive camera habit, I got to start paying out in L-glass just because of some eensy-weensy catch phrase theft???

...should have kept my mouth shut. LOL