An Incredily Newbie Type Question

[rufus5150]

It's a ratio of the focal length divided by lens's pupil diameter. A 100mm lens with a 25mm pupil will be f/4. Conversely, for a 200mm lens to have an f/4 aperture, it has to have a 50mm pupil.

The best way I've found to think about it (other than just memorizing the whole stop numbers) is that the result is a pure number -- that means a number without measurement or qualifications. This allows us the ability to talk meaningfully about f-stops regardless of what lens or focal length is being used.

Or if you really feel geeky, it's in the powers of the square root of 2 (being approximately 1.414):

sqrt(2)^0 = 1
sqrt(2)^1 = 1.4
sqrt(2)^2 = 2
sqrt(2)^3 = 2.8
...

 

[PhotoJunkieJen]

So the picture she originally commented on had an F-stop of 5.6. She suggested I up the aperture a full stop. So, that'd be 8? And 2/3 of a stop would be?
I'd probably grasp this better if I had my camera in hand... stupid 9-5 that keeps me from my real passions.

 

[Beth81]

The adage "The more I know, the more I find I have to learn" comes to mind for me.

Man, there are days I think I'm making progress... then there are others I see how far I have to go. I guess it's the chase that keeps things interesting though.

Exactly right...Some days just seem easier.

 

[tsaraleksi]

So the picture she originally commented on had an F-stop of 5.6. She suggested I up the aperture a full stop. So, that'd be 8? And 2/3 of a stop would be?

Yep, it'd be 8. I can't remember the 3rd stops off the top of my head but I think it'd be 7.1.

The easy way to figure them? More than likely your camera is set to 1/3 stop adjustments. So one click of the wheel is 1/3 stop, two clicks is 2/3 stop, 3 clicks is a full stop. The cool thing (I think it's cool anyway) is that this is also true of shutter speed, so if I want more shutter speed and am not really paying attention to the numbers I can just remember that I opened the aperture up by 6 clicks, then increase the shutter by 6 clicks.

 

[Flash Harry]

To stop "up" would be to open the lens to F4, stop down, (to close the aperture) would be F8 and going 1/3 - 2/3 I personally would use the exposure compensation dial rather than try altering other parameters, as its easier than working stuff out on the spot. H

 

[tsaraleksi]

Being able to effectively manipulate your aperture is much more than what you can control with exposure compensation.

 

[mrodgers]

Depends on the mode used and why the recommendation of adjusting the aperture. If it's because of DOF and in aperture priority, you would change the aperture. If in aperture priority and it's because of exposure, changing the aperture won't do a dang thing. You would have to change exposure compensation.

There is no exposure compensation in manual mode.

 

[PhotoJunkieJen]

Yep, it'd be 8. I can't remember the 3rd stops off the top of my head but I think it'd be 7.1.

The easy way to figure them? More than likely your camera is set to 1/3 stop adjustments. So one click of the wheel is 1/3 stop, two clicks is 2/3 stop, 3 clicks is a full stop. The cool thing (I think it's cool anyway) is that this is also true of shutter speed, so if I want more shutter speed and am not really paying attention to the numbers I can just remember that I opened the aperture up by 6 clicks, then increase the shutter by 6 clicks.

Sweet! I was wondering if that was the case. That makes life a lot less complicated.

 

[Flash Harry]

Being able to effectively manipulate your aperture is much more than what you can control with exposure compensation.

You've already confused this kid with your going "up" to F8 from F5.6, so now we have you effectively manipulating aperture with minor adjustments that effectively do nothing, do you think Nikon/Canon developers would calculate EC in 1/3 stops if smaller increments made such a difference, your fraction of a stop, whatever it is, is not likely to affect either DOF or exposure that is visible to the human eye, so therefore its irrelevant. The reason EC at 1/3 was introduced in film cameras was to tweak saturation in slide and neg film without unduly affecting an already good exposure, if its good enough for the manufacturers its good enough for me, you and anyone else to use. As for a new starter who's print is a full stop out, (whichever way I dont give a ****) I don't think your helping him get to where he wants to be. I also recommend he ditch manual and use AP or SP, with EC till he knows what he's doing H