hello i'm graham houghton and welcome to today's video now in this video i'm going to demonstrate
the differences between constant aperture lenses and variable aperture lenses now constant
aperature lenses are found in the panasonic lumix bridge camera range like the f-set 200
and the 300 330 and the very aperture lenses are found in the fz80 the f said 1000 2000 2500 etc
so first of all what's the difference between a constant aperture and a variable aperture lens
well with a constant aperture lens throughout the zoom range the aperture will stay at a fixed value
so if i set this FZ330 to f 2.8 as i zoom all the way from the 25 millimeter to 600 millimeter
effective focal lens it will stay at f 2.8 in the case of a variable aperture lens like this
FZ80 if i set f 2.8 at the widest angle setting of 20 millimeters when i zoom towards the 1200
millimeters effective focal length we'll find that aperture is now f 5.9 so it hasn't stayed
constant throughout its zoom range and that's why it's called a variable aperture lens now there is
a difference in construct between the two lenses which makes the uconstant capture lenses a premium
price compared to the variable aperture lens and in fact if you were trying to find a constant
aperture lens for something like a mirrorless camera you'd be paying something like three or
four times the cost of the same focal length lens in a variable aperture form so how do you discover
if you've got a variable aperture or a constant aperture lens to demonstrate that i'm going to
look at these two cameras the fz330 and the fz80 and i'll show you the differences and what you can
expect in your photography if you're going to be using either of these cameras let me demonstrate
now on these cameras how you can discover whether you've got a constant aperture or a variable
aperture lens and some other features of the lens itself let me switch over to the desktop camera
and here on this asset 330 you can see the wording around the lens and in particular i want to look
at this value here which is 1 to 2.8 it's only 2.8 there's no other number on here so this means this
is a constant aperture lens and it will stay at its widest aperture of f 2.8 if you zoom
all the way from 4.5 to 108 millimeters focal length now you notice here i'm using the native
focal length of the lens which is 4.5 to 108 millimeters to get to the equivalent full-frame
equivalent focal length you multiply these native focal lengths by the crop factor of the sensor
and in the case of a 1 2 13 sensor we're talking a 5.7 times crop so if you multiply 5.7 by the
native aperture you'll end up with the 25 to 600 millimeters that this lens is quoted to have
so that is the fz330 if we look at the f-set 80 and again let's go back to the desktop camera
you can see now on the lens decal we've got 1 to 2.8 but then there's a dash to 5.9 which means
that this lens will change its aperture from f 2.8 to f 5.9 over its range of 3.58 to 250 millimeters
again those values there of 3.58 to 215 and the negative focal lengths multiply again
by the crop factor of 5.7 and you arrive at the 20 to 1200 millimeters that this lens is framed for
so there you can see how you can tell if you've got a constant aperture lens
or a variable aperture lens i'll now show you how this works out in practice if you look at
the aperture on the back of the camera as you zoom through the range and then i'll go through some of
the scenarios where you might want to overcome those limitations if you're shooting outdoors or
even indoors for some photoshoots let's now look in practical terms how that works with your camera
let's look at the fz300 330 first of all and here on the back of the camera you can see
my aperture at the moment is f 2.8 and i'm at the widest angle setting
of 25 millimeters so you can see here on the lcd screen we got f 2.8
let's reengage the exposure meter now as i move from the 25 millimeter position if i go to 28
millimeters you can see it stayed at 2.8 go to 35 millimeters still at 2.8 50 millimeters
2.8 and you notice that as i'm through the whole range the camera is now still staying at f 2.8 so
this is the effect of a constant aperture lens now that doesn't preclude you from setting the
lens to any aperture one so if i wanted the sweet spot of this particular lens
which is around f4 then as i zoom again through the whole range you notice it stays at f4
let's look in contrast now to the fz8082
again we'll turn this camera on and have a look on the back of the camera
and again i'll set this down to f 2.8
so you can see on the lcd display we've got f 2.8 and i'll do the same test but i've gone to
28 millimeters you can see the aperture has now gone to f 3.2
go to 35 it's gone to f 3.9 and if i go to 50 millimeters you can see it's gone to f 4.7 and now
as i zoom towards the 1200 millimeter position you can see eventually we end up with an aperture of
f 5.9 you can see it on screen so as i zoom back down to
20 millimeters you'll see we've gone back to 2.8 so that's the effect of a variable aperture lens
and as with the fz330 it doesn't preclude you from setting in an f4 aperture so if i set in f4
you'll notice that it stays at f4 all the way up to about 50 millimeters which is a crossover point
of this lens for the uh variable aperture so at 50 millimeters we're at f 4.3
and then it will gradually move back to f 5.9 as we approach the 1200 millimeter position
so you've seen now how the focal length affects the aperture with the variable aperture lens which
means that you're losing two stops of light going from the wide angle to the telephoto position
that's important if you're going to be shooting something like birds in trees birds in flight that
sort of thing you've lost two stops of light which means you've got to overcome that in terms of the
exposure either by increasing your shutter speed so you're going to get a longer shutter speed
or you're going to increase the iso which means you're going to run into noise so there are some
consequences of changing the exposure by either using a longer shutter speed or a higher iso
there are some tips i can give you to overcome that obviously you want to try and keep the iso
low as possible ideally around about the 80 or 100 iso to do that you need additional lighting
if you're in a studio you could add extra lights or you could use flash if you're outdoors there
are some flash extenders which allows you to put a frame lens on your flash to extend that flash
light over a greater distance so you can see with these variable optical lenses when you approach
the full telephoto position you are going to be using that small f-stop to overcome that you need
to be using longer shutter speeds and run the risk of getting handshake or subject motion blur
with these favorable aperture lenses if you're shooting something like birds in trees
you need to be using something like a 500th of a second to overcome subject motion blur you
don't want the bird moving inside otherwise you'll get subject motion blur so to get 500
of a second at f 5.9 you're probably going to be using iso 800 or above which means you are
going to be running into some noise issues with these smaller sensor cameras so that's it for my
explanation of constant aperture versus variable aperture lenses hope you found that useful
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