lens descriptors

[davros]

I've been looking at getting a Nikkor 50mm lens, but I'm a bit perplexed with the descriptors. There are two 50mm f/1.4 lenses, D and G. Can anyone tell me what the difference is?

Thanks!

[etherial]

I've always found this link useful, it has the answer to your question:

http://www.overclockers.com.au/wiki/Lens_Specifications_Explained

[kiwi]

Simply the g is the new version with an internal focussing motor and therefore quicker to attain and track focus

Optically I think they are probably very similar


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[kingwheatie]

.... and the "D" has the aperture ring, good for the film cameras and can be used on the latest digital's as well just needs the apeture ring locked off @ f22(small sliding switch near ring).
The "G" lens has no aperture ring, aperture is controlled by command dials on the camera.

[Peppe]

I've always found this link useful, it has the answer to your question:

http://www.overclockers.com.au/wiki/Lens_Specifications_Explained

Thanks etherial, great reference.

Pep

[davros]

Thanks for the link etherial. So if I understand correctly, if I get the D version I will need to control the aperture from the lens instead of my camera? I'm using a D90 which has the built in AF motor so I'm good there.

[arthurking83]

Thanks for the link etherial. So if I understand correctly, if I get the D version I will need to control the aperture from the lens instead of my camera? I'm using a D90 which has the built in AF motor so I'm good there.

No!

you set the aperture to the largest number(smallest physical aperture setting) which on a 50mm f/1.4 AF-D lens is f/16(from memory??).
There may be a small locking tab coloured red on the aperture ring as well, and makingsure that's locked in place is a good thing.

Then on a D90 you control the aperture via the front dial, unless you've changed settings in the camera and reversed the control dials.

if you use any CPU'ed lens with the aperture ring, and the aperture ring is not set to the smallest physical setting you should get an F-- code on the top LCD.
You can shoot the camera in [M]anual mode, even tho the F-- code is showing on the LCD screen.

If you ever get yourself any older full manual lenses AiS or earlier then you do have to use the aperture ring to set the aperture value you require.

[I @ M]

Davros, you will be able to use the dial on the camera to set the aperture in the same way as you do with your current lenses. Before you attach the lens to the camera all you have to do is set the aperture to the minimum ( F22) and then lock it in place with the small slide that is there for that purpose. Once set you won't need to alter a thing again.

[davros]

I think I understand what I need to do, but can you help me understand why? Autherking mentioned that the camera will read F-- if the aperture is not locked at it's minimum. What would be the purpose for needing to manually lock the aperture? I'm guessing it's a hangover from film maybe? I'm just trying to understand why it wouldn't be locked internally at the factory.

Thanks for you patients and humoring me. I didn't get the benefit of starting on a film camera. I don't really know much about how the optics work, but I'm slowly getting my head around it.

[arthurking83]

Why they do this is a mystery, but it is a software technicality not a hardware one.

On the D300 and greater models(and I suspect the D200 as well :confused013) there is a Custom Menu adjustment that you can alter that allows the user to adjust the aperture either via the sub command dial OR the aperture ring(but not both at the same time).

Some folks just have to have the old feel of dialling in the aperture via the ring as it was done for a long time.

On the D90 and lesser models you don't get that option!

The reason you need to lock the aperture at the smallest setting is because of the manner in which Nikon cameras work(have no experience with other brands in a technical sense).

When you set the aperture value(on the camera) the aperture in the lens(called diaphragm) is held against it's wishes at the widest setting via a protruding prong on the back of the lens. As the camera is about to make the exposure the mechanism in the camera hold the prong to the correct position down to the aperture value you've selected.
The aperture is held in the wide open position by the camera for the purpose of easier focus and a brighter viewfinder. Faster lenses.. such as the 50/1.4 are much brighter through the viewfinder due to the larger iris at the back of the lens. if you have a 18-55 kit lens(which is f/5.6) you will clearly see that against the 50/1.4 lens.

The reason it operates the aperture in that manner may be many and vaired, but one thing I do know is speed.
As the natural tendency for the lens is to keep the diaphragm in the closed position the mechanical force exerted by the camera is in only one direction, and that is to momentarily hold the aperture down for a brief moment for the exposure. After the exposure is taken the camera simply releases the diaphragm a the lens will naturally allow the diaphragm to settle where it needs too.

if the camera was to operate in a reversed situation, where the diaphragm is kept closed all the time the viewfinder would be impossibly dim at the smallest aperture value.. and with some f/32 aperture lenses this would mean (basically)totally black!

you can see the workings of the aperture easily with your gear:

at the back of the lens is a small protruding tab. It moves in an arc and when you do slide it, it will open the diaphragm. Good way to see the smooth operation of an aperture in a lens.
Some oldies have known to become contaminated with oil.. and then dust and the operation is not then so smooth.. BAD! for exposure as the camera will have no real idea of the actual aperture value the lens will produce.

Also on the camera is a small button on the front face of the body down near the lens, called the DOF Preview button. It's the default setting for the camera, but can be changed in what it actually does on the D90!!). Set an aperture of f/22 and press the DOF Preview button and watch the view go dim!
Note it doesn't work in LiveView mode either! :action:(and that is the most incompetent design of the Nikon system!!.. among a few others) The reason you use DOF preview is to judge how deep DOF will be as you compose. You can get a semi decent idea of how it will look even though the viewfinder is going to be dim.
The reason for DOFPreview is that the view through the viewfinder for DOF is not accurate unless you set f/5.6(specific to most DSLR's). If you set an aperture larger than f/5.6.. such as f/4, the DOF preview button is useless.. does nothing! the ground screen matte in the viewfinder is optimised for f/5.6.
(you can get alternate VF screens that change that if you like too).

[I @ M]

davros, I remember a similar question coming up in the past and found a thread that has a picture of the tabs that must be aligned and locked on 50mm F/1.8.

Have a quick read of http://www.ausphotography.net.au/forum/showthread.php?t=50545

[arthurking83]

Also from memory, the locking tab doesn't HAVE to be locked in for the camera to operate correctly(someone with a Nikon lens with such a system may confirm/deny that tho, as I don't have any similar lenses to test any longer.. my 80-200/2.8 is now gone).

The locking tab is a pure mechanical device and the camera doesn't know about it. It's there simply to decrease the chance of inadvertently moving the aperture ring and getting one of those DOH! moments as the camera refuses to operate. :D

[davros]

that makes since. Thanks again for the info guys!

[N*A*M]

there is a little switch on the camera body around the perimeter of the lens mount, near the Func button that needs to be pressed. think of it like the door switch for the light inside a car. it needs to be pressed to confirm that a lens is present. on G lens, there is no aperture ring but the lens will have a tab that presses this switch when it is mounted. on an AF/AF-D lens, this tab is on the aperture ring but will only press the switch when set to minimum aperture. the orange locking tab is there to ensure the aperture ring doesn't move.