Best aperture for 17-40 f/4 L glass?

[eorlingas]

I've always heard that it's best to shoot a couple of stops below the wides aperture - for my glass the widest is f/4, so would I choose f/6.3?

When I dial the aperture, it goes from f/4 to f/4.5, and then from f/4.5 to f/5 and then f/5.6 and then finally f/6.3 - so two full stops would be f/6.3, right?

Thanks!

 

[RyanLepik]

The answer is yes.
--
Ryan

 

[kristian1]

two full stops from f4 is f8

The answer is yes.
--
Ryan

 

[jrscls]

f4 to f5.6 to f8 to f11 etc.

 

[Bobby H]

For the best level of sharpness, just about any lens will be at its sharpest starting at f/8 and perhaps keeping that maximum level of sharpness to about f/11. Naturally, a lens with a larger aperture will provide greater shooting flexibility and artistic versatility.

 

[BAK]

Your camera is set to increase (decrease) exposure in one third stops. That's why you get 4.5 and 5 between 4 and 5.6.

And remember, there's always been rounding off in photography, so the numbrs are not always precise.

for instance, 1/2 to 1/4 to 1/8, and then to 1/15 and 1/40 and 1/60, and then to 1/125 and 1/250.

As for your original premise of stopping down two stops -- yeah, sort of, mostly, and it depends.

Sometimes it is one stop, sometimes three stops, often two stops, maybe a stop and a half measured with some fancy instruments but invisible to the eye.

Also, depth of field gts incvolved. Some lenses focus on a flat field -- imaginethe side of a barn. Others focus on an arc always the same distance from the camera. Imagine a string tieds to the lens and then dragged from one side of the frame to another. It would only touch the barn straight ahead.

Stopping down increases the depth of field, which compensates for the arc cf flat field situation.

BAK

 

[BAK]

The focal length setting of a zoom may or may not affect the sharpness at any particular stop.

 

[Garen]

Greetings,

I've always heard that it's best to shoot a couple of stops below
the wides aperture - for my glass the widest is f/4, so would I
choose f/6.3?

When I dial the aperture, it goes from f/4 to f/4.5, and then from
f/4.5 to f/5 and then f/5.6 and then finally f/6.3 - so two full
stops would be f/6.3, right?

Wrong, 2 full stop would be f8 the sequence is as follows

4.0 --- 4.5---- 5.0 ---- 5.6 1 stop

5.6 --- 6.3 --- 7.1 ---- 8.0 2 stop

Your camera is set for 1/3 stop not 1/2 stop.

Thanks!

Best regards,
Garen
--
Who says it can't be done?

 

[ARShutterbug]

The f/stops in the scale that you're trying to use:

f/4
f/4.5

f/5.6
f/6.7

f/8
f/9.5

I frequently use the 17-40 wide-open at f/4. The depth-of-field that you need and the available lighting determine the aperture that you should use.

--
http://www.pbase.com/arshutterbug/

 

[eorlingas]

Yes, I realize that which aperture I end up using will hugely depend on the amount of lighting available; I'm talking about a situation in which lighting is of no concern (i.e. more than enough light present, ambient or otherwise) and where the depth of field is of little concern as well...

In such a situation, I'd choose to use f/8 whenever I can?

Thanks!

 

[wrider]

Do whatever works for you. That is why you learn the trade. I have shot thousands of pics with my 17-40 and blown many of them up to 16x24 or bigger. I never print anything smaller than 8x10 on my Epson 4000. I don't need a spec sheet or a calculator to tell me that the lens works best between f8 and f11. If that is what you want to know, there it is. It also works great at other apertures and it helps to use a tripod. If you are just worried about getting the "best possible image", there is a lot more to it than what the sweet spot of the lens is.
Good luck.
Happy Holidays,
--
Wendell
http://www.wendellworld.com

'Not everything that counts can be counted, not everything that can be counted counts.'
Albert Einstein

 

[neographikal]

The aperture you need to take your shot the way you want it creatively.

These questions are just madness, what are you doing? Are you photographing or taking lens tests?
--
Lens reviews from users with full size examples: http://www.yourlensreview.net

 

[Anthony de Vries]

It's an L, not the kit lens.

You pay that large amount of cash, so that the lens doesn't get terribly soft at wide open aperture.

Check this test for comparison:
http://www.photozone.de/8Reviews/lenses/canon_1740_4/index.htm

The center has excellent sharpness at ANY aperture setting.
The border is OK wide open, and increases to excellent when stopping down.

That means that in most cases, you can forget about the sweetspot of the lens, and simply use aperture for selecting the correct DoF.

Only when the borders are very important, would you stop down for sharpness there.

 

[ARShutterbug]

The image quality is dependant on DOF. When the DOF isn't important, I shoot wide-open and increase the shutter speed.

--
http://www.pbase.com/arshutterbug/

 

[Jovo]

Two stops is generally the case with consumer lenses but the Ls generally perform best wide open. For instance both my 400mm f/5.6L and 70-200mm f/2.8L are sharpest at maximum aperture. With the 17-40mm f/4L I find it is best f/4-5.6.

I've always heard that it's best to shoot a couple of stops below
the wides aperture - for my glass the widest is f/4, so would I
choose f/6.3?

When I dial the aperture, it goes from f/4 to f/4.5, and then from
f/4.5 to f/5 and then f/5.6 and then finally f/6.3 - so two full
stops would be f/6.3, right?

Thanks!

--

 

[Perdu]

The 17-40 is definately better at F8. If you can, you'll get better results stopping it down. At least mine is not that good wide open. You cannot compare a wide with a Canon large tele, which wil let you open it up and still be great.