New 7D mk ii, Samsung nx1, Sony a77ii

[dcstep]

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<p>David: Yes, but exactly the same is true of teleconverters - you get more reach in return for reduced low-light performance and increased depth of field. I don't claim that DX doesn't make sense for those who always want long lenses - one can argue the merits of larger AF area coverage (vs density of focus points), we would be talking about a <em>perfect</em> 1.5x teleconverter, etc. (and, of course, the DX camera is smaller, cheaper and lighter). Equally, one could talk about the merits of a larger finder and the potentially larger dynamic range from larger sensor sites. I just don't think the phrase "equivalent in a full frame camera" is that informative unless you really want to consider a full-frame sensor as being equivalent to its DX crop, or a 5x4 film as equivalent to an APS roll of the same emulsion.</p>

 

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<p>Wonderful discussion Andrew, thanks for engaging.</p>

<p>Yes, as a user of 1.4x and 2.0 time teleconverters, you do get more reach and reduced low light performance, not unlike with a crop-sensor body. It's a trade off or compromise, for sure. In good light, there's hardly any difference, EXCEPT the bodies ability to AF at f/8. For example, with a 2.0x TC-III on the Canon 5D MkIII, the AF lag can be up to one-second for ANY mistake in AF technique by the user. With the 1.4x TC-III on the 5D MkIII, the lag is only around .1-sec. That's a huge difference in practice. d</p>

<p>If you're able to use the 1.6 crop of the 7D MkII, with a 1.4x TC and get an effective focal length that exceeds a 5D MkIII with a 2.0x TC-IIIk then you'll get much fast initial AF capture, assuming that the 7D MkII is at least as good as the 5D MkIII. </p>

<p>With 1.5 and 1.4x teleconverters, there may not be much practical difference, but when you start using the 2.0x converters and get the native aperture down to f/8, then there's a big difference, at least on the Canon cameras below the 1D X. </p>

[Andrew Garrard]

<p>Thanks David (and you!)</p>

<p>I agree that there's an autofocus difference. My take on that - which is not entirely qualified - is that the same AF module behaves like the same pixel density. In the FX bodies, the AF module covers much less of the frame - bad for positioning, but good for differentiating small parts of the image - compared with DX. Stick a teleconverter on and the AF module gets less light (and light from a narrower angle). If the FX AF module had the same coverage relative to the sensor size, the sensor sites would be larger - I suspect making up for the effective sensitivity loss caused by the teleconverter. Of course, the optics of the mirror box mean that the FX AF sensors can't cover such a large area as in DX. By symmetry, if the DX AF module increased in density to match that of the FX bodies, I'd expect it to lose low-light performance. But I may be vastly over-simplifying.</p>

<p>I certainly agree that AF performance is important, though (it's one factor in my desire to upgrade from a D800e to a D810). Nikon, too, can't handle f/8 with most of the AF points. I guess we'll see how AF modules - and particularly on-sensor phase detect - evolve in the future.</p>

<p>Michael: I agree about the history, but I don't know how much of Nikon's income comes from cameras compared with lenses. If Nikon really felt that way, I'm sure they'd be making more lenses for other mounts (which hasn't seemed appealing since the Canon rangefinder days). A mount deal that applied only to the NX1 and didn't allow competition with consumer DX DSLRs or the FX range seems a bit convoluted, though. I've no idea where Samsung's glass is ground, but given that Nikon do so much in China and given the bad history between Korea and Japan, I'd be a little surprised if that was where they chose to source. But I've no internal knowledge, and successful companies make practical decisions, so you may be right.</p>

 

[dcstep]

<p>Andrew, with Canon and its big super-telephotos when combined with teleconverters, it's not a crop vs. full-frame difference, but a battery voltage difference. The 1D X and the 5D MkIII have essentially the same AF systems, with only a difference in the x-type AF cells. They're both full-frame, but the 1D X has around 50% more battery voltage. With a 500mm plus 2.0x TC, the 1D X locks in after only .1-sec., where the 5D3 can take up to a full second in the same situation. <br /><br />The 7D MkII is equipped with a new battery, that's got about 10% more voltage and is backwards compatible, so I'm anxious to see if it narrowed the gap. Even if it hasn't, then I can use a 1.4x TC instead of a 2.0x to get similar effective focal length.</p>

<p>At shorter focal lengths, such as 300mm and 70-200mm, you can notice the differences, but they're not near as extreme as with the 500 and 600mm lenses.</p>

[Andrew Garrard]

<p>Belatedly (sorry, away), thanks David, and interesting. Nikon also have higher voltages on their bigger bodies, and some lenses can make use of it. I'm not sure how relevant it is to the big superteles, though - practically, they're all using relatively lightweight internal focus groups anyway. I don't know that a TC should make a difference in the speed of an AF group, beyond requiring more sensitivity and accuracy. Ironically, my TC-16A (Nikon's autofocus 1.6x teleconverter for manual lenses) is actually very fast, because it doesn't have much to move. It can't really cover much of the focus range of a 500mm, though - you still have to get focus roughly right manually.</p>

[dcstep]

<p>Thanks Andrew, but I wasn't making that stuff up about the 5D MkIII taking a full second to acquire focus while the 1D X will do it in a tenth of a second. For my side-by-side comparison, I was using the latest EF 500mm f/4L IS-II and the EF 2.0x TC-III on relatively new 5D MkIII and 1D X. The difference was HUGE.</p>

<p>Cash concerns kept me from buying a 1D X (I used a loaner from Canon for the comparison) so I've continued to struggle with my 2.0x converter on my 5D3. The slow down with the 1.4x TC is not near so bad, but there is a little slow down. With smaller lenses, such as my EF 70-200mm f/4L IS, there only a small slow down, that's easy to manage. The super-telephotos are where it becomes a big problem, particularly when trying to track birds in flight.</p>

<p>Maybe it's a Canon-only issue. What happens when you put a 2.0x TC on your big Nikon?</p>

[Andrew Garrard]

<p>I believe you, David. I'm just not sure why it should be happening! I'm curious whether it's definitely the batteries, or if it's something in the AF system. I don't suppose the battery grip on the 5D offers a higher voltage? (The D700 - and probably D800 - does let you increase the voltage with the right batteries, so you can see whether some of the limitation on those "consumer" cameras is power based rather than AF based.)<br />

<br />

I'm assuming that question was to the group - I don't have a 2xTC, and my only "big Nikon" is an F5... but many reviews have suggested that the D810's AF seems to keep the D4s's quite honest. I don't know how many lenses have been tried.</p>

[dcstep]

<p>Thanks Andrew.</p>

<p>My experience is consistent with other Canon users on birdphotographers.net. The battery grip does not offer extra voltage. It'll be interesting to see the 7D MkII, which has slightly higher voltage than the 5D MkIII and the battery is backwards-compatible. </p>

<p>As for the AF of the D810, I don't know, but I've stood by Nikon users with the D800, shooting eagles in flight, and they were having trouble with both acquisition, using a bare 600mm, and buffer capacity. My friend with a D4 was having much better luck and keeping up with me easily, with his bare 600mm. The D810 must be a big step forward from the D800 in regards to AF and buffer capacity. (The files are fantastic, IF you get the subjects in focus and the camera lets you take the shot).</p>

[ilkka_nissila]

<p>With a 500mm lens, full frame camera, at f/4, with subject distance 10m, the depth of field is about 9cm. If a 2X TC is attached, the lens becomes a 1000mm f/8, and the depth of field at the same distance is reduced to about 4cm. Thus the lens needs to be focused more precisely to obtain satisfactory results consistently with the 2X TC attached. This increased precision can be achieved by slowing down the focus group movement so that the camera has time to process the AF sensor data and respond to it adequately. Another approach is if the processing power can be increased, run the AF motor at full speed and focus the data from the AF sensor more quickly, leading to the combination of high speed and high precision. I guess the dual processor architecture of the 1D X is responsible for this feat.</p>

<p>With Nikons, I felt the TC-20 E III yielded high quality images with the 200/2 stopped down 1-2 stops, but autofocus of this combination (with the D800 body) was not precise enough for use for sailing and aviation photography. With the TC-14 E II the autofocus was very precise, at all distances, however. I experienced similar problem in my brief testing of the 200-400II, i.e. at close distances good results were obtained using the 2X TC, but a greater degree of variability in focus was obtained at longer (30m+) distances. With the 200/2 I know it's not about the optical quality of the combination since I got very good results when using the lens with the 2X TC for landscape photography, with live view focusing. My conclusion was that the 2X TC isn't very useful to me. Currently I use the TC-14 E III with D810 and it works well but I cannot test the 2X with the new camera since I no longer own that TC. </p>

[Andrew Garrard]

<p>David: Yes, that's one reason I want to upgrade to a D810. :-)<br />

<br />

Ilkka: Yes, I can see why AF would be slower with the teleconverter, just not why body voltage should be an issue. (If you need to run the AF more slowly over a teleconverter, if anything a higher voltage should help more in the non-teleconverted case.) I completely believe that the speed of the AF electronics may be involved. So I'm in no way disputing what David is saying, I'm just trying to understand the mechanism. And I'll take your advice about a 2xTC on the 200 f/2 as a way to persuade my wife that I really need a 400 f/2.8. :-)</p>

[dcstep]

<p>Just for the record (I know this is a Nikon forum, but a Canon is in the thread title), the Canon 1D X, the 5D MkIII and, hopefully, the 7D MKII, all have excellent AF accuracy with the EF 2.0x TC-III on Canon's 500mm and 600mm super-telephoto lenses, either Series I or II. I'm addicted to mine and only curse it when trying to keep AF on birds in flight while the AF hunts around for a subject.</p>

<p><a title="Waxing Gibbous Moon by David Stephens, on Flickr" href=" src="https://farm3.staticflickr.com/2948/15422172021_bac9cfd9cc_c.jpg" alt="Waxing Gibbous Moon" width="800" height="800" /></a></p>

<p>Canon 5D MkIII, EF 500mm f/4L IS, EF 2.0x TC-III, hand held.</p>