11 replies to this topic

[Johnb]

Hi Guys and Girls, It seems common sense to me that there is no point in using aperture priority if the lens you are using is just an f4 or f2.8 and that you may as well just stay in auto. Am I right ???

 

Cheers

[Fletch]

I have not used a fixed aperture lens so I don’t know if the camera digitally changes anything, however, I assume that it will select the best shutter speed based on available light and iso. If that’s the case then AP is still a valid choice. Of course if I’m wrong someone will be able to correct me.

[Bengan]

Hi Guys and Girls, It seems common sense to me that there is no point in using aperture priority if the lens you are using is just an f4 or f2.8 and that you may as well just stay in auto. Am I right ???

 

Cheers

 

I have never heard of a lens with a fixed aperture of only f4 or f2.8. Are you talking about zoom lenses with aperture f2.8 or f4 over the whole zoom range? If not, could you give an example?

[Fletch]

AF-S NIKKOR 70-200mm f/2.8G ED VR II | Nikon

[Nikon Shooter]

In Auto, you give the camera all your decision discretion and
this may render results you may not have expected.

In aperture priority, at least, you know what DoF base you're shooting.

I have a 500mm fixed ƒ8 mirror lens I use in A mode all the time.

[Johnb]

Sorry, yes, these are zoom lenses.

 

I have the Nikon 70-200 f2.8E and I know Nikon have brought out an f4 version too.

[Nikon Shooter]

My post is still valid for all lenses!

[Jerry_]

There is well a number of very good reasons to use Aperture Priority, Shutter Priority or Manual.

Indeed the 2.8 or 4 (or whathever the max Aperture) of your lens is an indication for its widest opening. Having it constant, means that this max Aperture is available for any focal length of that lens, it does not mean that it is the only available aperture opening.

As already mentioned the Aperture setting allows to decide the DOF of a given capture.

Having large max apertures mostly helps by the fact that for focussing - or the camera autofocussing - the aperture is set on wide open. Thereby a large available aperture allows to better and faster focus in low light situations.

[Merco_61]

Aperture priority is for when you want full control of the aperture. Even if the 70-200E is good wide open, it is still not as crisp as when you close it down a little bit. You might want to close it down more to get a wider depth of field or sometimes shoot it wide open to keep ISO down and shutter speed up. The camera body isn't a mind reader, thankfully. You need to be able to take control over all parameters to get the results you want. Like Nikon Shooter said, A mode is valid even with catadioptric lenses with fixed apertures.

[Dogbytes]

Seems to me the OP thinks that a constant aperture lens and a fixed aperture lens are the same thing.

In case anyone is still confused, lenses like a zoom which stays at f2.8 or f4, for example throughout its focal length range, are ‘Constant Aperture’ lenses. You can still adjust the aperture - most go to at least f16 or f22.

Fixed aperture lenses are rare these days (probably always have been) and are usually restricted to fixed focal length (prime) telephoto lenses of the catadioptric or ‘mirror’ type.

[Johnb]

Thanks Dogbytes.

 

It seems then I am totally missing the point.

 

I thought that if the lens was f2.8, that is what it was. It could not be changed. Ie for what ever the lighting condition, the camera would set the Shutter speed to suit the f2.8 aperture, and that was that.

 

That's basically why I bought the f2.8 over the f4 to get that little bit more usage in lower light situations. At double the price !!!!!!!

 

Yea, and I do see that you still have control over all the other attributes.

 

Thanks guys. I am getting there slowly.

[Johnb]

Yep you are right, that is what I was thinking. It is all starting to make sense now.

 

Cheers Jerry.