Lens question

[mattchewone]

Right guys I have what is possibly a bit of a dumb question.

When I read people saying about shooting at the lowest f/number of there lens to get the best out of focus background I understand this but I get a bit confused when people say a lens is usually softest at it's lowest f/number and to stop it down.

Is this relevant with all lenses?

So say my 17-85mm f/4 it's going to be soft and its better at say f/5.6 or above?

Thanks (I get quite confused with how the f/numbers actually go, I'm sure people say stop it down even though the number is getting bigger, that just throws me out lol)

 

[amtaylor]

The aperture is a fraction so as the number gets bigger it is a smaller fraction if that makes sense. Most lenses will usually be sharper when stopped down a stop or 2 so an f4 lens will be sharper at 5.6 or 8 or perhaps 11 however after 16 it can less sharp again due to distraction.

Just adding to the aperture terminology. Low number equals wider aperture equals narrower depth of field. Stopping down equals higher number equals narrower aperture equals greater death of field.

 

[mattchewone]

I think that pretty much explains it all. Thanks that was very helpful.

Any chance you could run through what they are all the way through?

 

[amtaylor]

I think that pretty much explains it all. Thanks that was very helpful.

Any chance you could run through what they are all the way through?

Sorry I don't understand what your asking?

 

[mattchewone]

Sorry lol. I assume they start at f/1.2 then how do you know what's next?(I know it's f/2) but its not like they double each time. Is there a way to remember for example?

 

[amtaylor]

Sorry lol. I assume they start at f/1.2 then how do you know what's next?(I know it's f/2) but its not like they double each time. Is there a way to remember for example?

It depends on whether you go in third (which is usual) half or full stops. Here is a Wikipedia article if you scroll down it gives a chart
http://en.wikipedia.org/wiki/F-number#Typical_one-third-stop_f-number_scale
A good thing to remember is if you double the f number you have gone down 2 stops.

 

[Canon Bob]

Sorry lol. I assume they start at f/1.2 then how do you know what's next?(I know it's f/2) but its not like they double each time. Is there a way to remember for example?

The "magic number" is 1.414 (ie, the square root of 2) and then rounded up for convenience.

Bob

 

[jonpeter001]

All Ai and Ai-s lenses are full frame or FX. Except for a select few which are listed in your manual as unsafe to use (some old fisheyes and 1 or 2 mirror lenses) they are all compatible with your camera. Of course these lenses are manual focus only.

You will have to tell your camera the focal length and the maximum aperture of the lens but, once again, that's explained in the manual
Source(s):
nikon shooter