robin_sibson1

<blockquote> <p>That assumes you are willing to crop your 5D3 images to match those of the 1D4 and are happy to see the subject considerably smaller in the viewfinder. Not ideal.</p> </blockquote> <p>"Reach" = ppd (pixels per duck). Provided the frame is big enough to contain the duck, or such part of it as you want to include, then at one level how much more of it there is matters not at all. At another level, anyone who has done any wildlife photography, particularly birds in flight, will be well aware of the advantage of a slightly wider FOV, which makes it easier to follow the subject. More ideal, not less.</p>

<p>Extra reach? Not a lot. The pixel pitch of the 1DIV is 5.6um, that of the 5DIII is 6.25um, so the gain is just under 12%.</p>

<p>Mark, be aware that you are standing at the top of a long slippery slope. Once you start buying L-series lenses, it is hard to find a way back. It is pretty safe to assume that your first L lens will spend a lot of time n your camera, and a general-purpose standard zoom rather than a UWA zoom is the sensible choice. The original-version 5D has quite a coarse pixel pitch, so it does not make quite the same demands on lenses as the more recent 20+ Mpixel bodies, and you are very unlikely to be disappointed with a 24~105. Distortion and vignetting at the 24mm end can be corrected with almost no downside in DPP. Compared to other 24~XX Canon alternatives, the 24~105 is reasonably priced, and since it is often sold as a kit lens with the 5D series and 6D, it is readily available s/h.</p>

<p>Mark, enjoy your new purchase. You have been given good information about servicing, but there is one other aspect of the 5D (original) that you should be aware of. If you want to connect your camera to a PC (for example, to change the owner name) then you will have to find a PC running Windows XP and a copy of EOS Utility no later than Version 2.4 (and possibly a driver). Canon (disgracefully in my view) withdrew EOS Utility support for a whole bunch of early DSLRs (including 1D-series bodies) with 2.5. Transferring image files to your computer is not a problem – just use a card reader – and if you like using Digital Photo Professional, be reassured that it supports all CR2 files including those created on a 5D.</p>

<p>The 70~200 lenses have completely internal zoom and focusing, and so can easily be sealed. But several of Canon's WA zooms move the front element slightly during zooming, although this happens within the overall fixed length of the lens barrel. Presumably it would add to weight/bulk/cost to seal the join between the lens barrel and the front lens group, and Canon have chosen not to do this but rather to leave the user to complete the seal with a filter. Perfectly rational decision, even if you don't agree with it.</p>

<p>In fact the new 16~35/4L IS is noticeably longer (113mm v. 97mm) and heavier (615g v. 475g) than the 17~40. Both take 77mm filters and have a diameter of 83mm, but the 17~40 reaches that diameter only at the front end, whereas the 16~35/4L is fat over most of its length, so will seem considerably bulkier. The 16~35/2.8L II is 112mm long and weight 670g, so the new lens is much closer in size and weight to the f/2.8 lens than to the 17~40. The f/2.8 is wider at the front end, taking 82mm filters rather than 77mm filters, but, like the 17~40, the rest of the body is slimmer than the front end.</p> <p>Interestingly, the new lens takes a new hood size, 82 rather than the 83 fitting common to a number of earlier lenses. Presumably it will have a locking catch like the hood for the 24~70/4.</p> <p>The computed MTF charts suggest that the new lens will set a benchmark for UWA zoom performance, and it does not seem to be outrageously highly priced, so it is likely to be uch sought agter.</p>

<p>Your problem arises because you have fitted an extension tube but no EF lens. Ever since the introduction of the EOS system, attempting to fire a camera with this setup has caused some form of lockup. The reason is that the camera detects the presence of the tube as an indication that it should be communicating with a lens, and if no lens is present this creates an anomalous situation to which the camera responds by locking up when the shutter is released. It appears that this happens by design, or perhaps by failing to design in a graceful response. It also happens when an Extender is fitted with no lens.</p> <p>Two different recognition mechanisms have been used. Earlier EOS cameras had a mechanical switch built into the lens mount which was closed by the insertion of the bayonet of the lens into the mount. Later cameras use electrical detection, I believe by using the two pins on the camera that both contact a single pad on the lens. Presumably your 12mm tube (is it a Canon tube?) is not making this connection, although I have not heard of this effect before.</p> <p>Anyhow, be reassured that there is nothing wrong with any of your kit and the EF25 tube is compatible with your camera provided a lens is attached as well.</p> <p>You may notice that the EF25 tube actually has the extra pins at the lens end that are used to signal the presence of an Extender or Life Size Converter. On the EF25 no use is made of these extra pins and I have always assumed that the relevant component in the EF25 was taken from the Extender parts bin to save on production costs.</p>