Setting the Aperture when using a TC

[brian_bahn]

<p>I have a Kenko 300 Pro 1.4x tele. Using it on my D300 with 80-200 2.8. Since it is one stop difference it makes the 2.8 an f4.0 correct? So when shooting in Aperture priority mode do I set the Aperture to 4.0 or can I leave it at 2.8? I say this because when changing between the two values the meter does change. But it does seem to expose correctly at the 2.8.</p>

<p>Sorry if this seems simple I just can't get my head around the technical part of it, which I usually can.</p>

<p>Thanks</p>

[ShunCheung]

<p>I don't have the Kenko, but when I use the Nikon TC-14E with an f2.8 lens, the maximum aperture the D300 (and other DSLRs) will show should be f4, not f2.8. Therefore, you don't need to make any further compensation.<br>

With the TC added, you lens simply becomes a 112-280mm/f4 lens.</p>

[brian_bahn]

<p>Shun,</p>

<p>I can actually dial the value down to 2.8. Not sure if the camera reads the Nikon and Kenko differently or what. I realize it's still actually closing/exposing to f/4, it's more a question of what goes on with the meter. The lens is wide open when it meters rigth and calculates based on what I set the A value to right? So am I getting an accurate exposure if I have it metering at 2.8? It seems to come out accurately. Not sure what's going on.</p>

[joseph_wisniewski]

<p>You can leave it at 2.8. That will cause the lens to be an "effective" f4 280mm. Whatever you set, you're actually getting a stop less. This really only matters when you're using a hand held light meter. If you set up studio flashes, and your flash meter said f16, you'd set the camera to f11, not f16. Because at the f11 setting, the lens is effectively f16.<br>

With the AF lenses, the TC can't provide a corrected aperture readout to the camera, the way Shun's AF-S can.</p>

[ShunCheung]

<p>As Joseph points out, the TC will reduce the amount of light entering the camera by a stop so that the TTL meter will automatically compensate for it anyway.</p>

<p> But I am surprised that the Kenko TC doesn't have the electronics to correct things on the camera's display.</p>

[joseph_wisniewski]

<blockquote>

<p>Not sure if the camera reads the Nikon and Kenko differently or what.</p>

</blockquote>

<p>AF-S and AF-I lenses provide "corrected" apertures to the camera when used with Nikon TC-E or Kenko teleconverters.</p>

<p>Nikon cameras have 7 or 8 contacts. Regular AF lenses like yours have 5 contacts (they skip 2 of the contacts on the camera for historical reasons). The newer AF-S and AF-I lenses have 10 cointacts. Nikon and Kenko teleconverters have 10 contacts in front, facing the lens. and 2 of these contacts are so that the converter and lens CPU can talk to each other, enabling the corrected aperture.</p>

[ShunCheung]

<p>Oh, I guess we are talking about a non-AF-S version of the 80-200mm/f2.8.</p>

[walterh]

<p>"But it does seem to expose correctly at the 2.8."<br>

Because the exposure is measured through the lens. This is why Joseph pointed out the difference to the external light meter that is not affected by the lens and its effective f-stop.<br>

Slight deviations may still occur due to "interpretations" by the matrix metering system.</p>

[Rene11664880918]

<p>That seems perfectly normal. I used both types of TCs, Kenko and Nikon TCeII. The Nikon TC automatically changes the read out on the display of the camera but not the Kenko. If you were using the Nikon TC you wouldn't be able to dial down to 2.8. It doesn't seem to affect on the wide side but in your case when you want aperture smaller than 4 enter the right aperture wanted and it will work. You can always check it on the info of the shots.</p>

<p>Shun... It works the same with my AF 180 or AFS 300. Strange but it doesn't have the electronics needed even though it will AF both lenses.</p>

[brian_bahn]

<p>Shun sorry, yes it is the AF-D version.</p>

<p>So if I understand correctly I am OK, leaving ti at 2.8 and the meter is reading what I will actually get when I click the shutter, it's just that the display on the camera allows me to set it at 2.8 but it really is "seeing" f/4.</p>

<p>So in reality I'm not getting a different exposure than what I think I'm gettign when I set it to 2.8 and see the shutter speed it's reading?</p>

[ShunCheung]

<p>Would have been a miracle if the lens remained at f2.8 after adding the TC. :-)</p>

[brian_bahn]

<p>LOL. Yeah I knew it wasn't staying at f/2.8, I just wasn't sure how the camera was handling it and what result I should shoot for/expect.</p>

<p>If it would have remained 2.8 I would have been sure to let folks know of the anomoly, and them promptly reversed engineered it and went from there. Haha</p>