Vagrant thought for a Friday evening... We used to see the question come up occasionally of whether it was better — i.e., the less objectionable compromise — to use an extender or to crop. The consensus was generally that the extender beat cropping, in most cases and with most combinations of equipment.
But I don't think I've seen such a comparison done recently, with Mark III and later bodies. We now have more resolution and therefore more cropping leeway, and the flip side is that the higher resolution also requires more quality from our lenses.
Any chance that in the case of the Mark IV, for example, these two factors might combine to render extenders "obsolete?"
Even the mighty Mark IV will have lower pixel density than many crop bodies, on which people still benefit from extenders. Higher resolution trumps extenders on lenses which are, un-magnified, already strained to the limit of their resolving power; however, there are still plenty of lenses that have more resolution to spare (at least in the center and at optimal apertures). The continued push to higher-resolution bodies is also driving the production of matching higher-resolution lenses (there will likely be more version II & III's of already good lenses) and better teleconverters (Nikon's new aspherical TCs will eventually prompt some response from Canon).
Unfortunately I don't have the link, but a few years ago I read about this as well. The guy who wrote the article had some pretty compelling examples for his conclusion that the 1.4x TC was worthwhile but that the 2x was not better than shooting with the 1.4x and then cropping and interpolating the image to the equivalent of the 2x. In other words it could go either way.
I think it depends on how you look at this. If you take an image with the 8MP Mark II and the same image with the 16MP Mark IV, then crop an 8MP portion out of the IV image, it will give you a field of view as though you had used a teleconverter on the Mark II. Assuming the lens used wasn't out resolved by the IV's sensor, my guess is the IV crop will be somewhat better than a TC on the Mark II to match the 8MP IV crop. Of course there are differences between cropping and a TC, but based just on field of view and sharpness in the end, I'd rather crop the IV than put a TC on the Mark II.
My feeling is opinions about this will depend on each photographer's end goals/needs. From a sports/photojournalism point of view (and a market the IV is directly aimed at) being able to crop deeper into the file offers more flexibility than teleconverters. If whatever you're shooting suddenly changes (i.e. sports) and you're suddenly too tight while using a TC, you're screwed. If instead you shoot a bit loose, you can always crop later for optimum framing. I shot a hockey game tonight with a 70-200 and a 400. I could have put a 1.4x on the 70-200 because from the overhead position it was loose when covering the net nearest to me. But instead I cropped when needed and the quality is fine for the end purpose (newspaper). But others will want to extract the full amount of image quality possible from the camera's full resolution rather than crop. If that was the case then I would use a 1.4x TC without hesitation, but I am somewhat skeptical about the 2x, at least in situations when I'll have to shoot wide open. If I could stop it down 1-2 stops then maybe.
From my pov at least, the 2x is obsolete. I rarely use it. I bring the 1.4x still, but don't use it as much as I used to. But I'm also not photographing inaccessible birds, wildlife, etc... A football field is a fixed length and I know I'll never be farther than X from the action.
mpmendenhall wrote:
....there are still plenty of lenses that have more resolution to spare (at least in the center and at optimal apertures).
I think that's a key point and relevant to each photographer's environment. I know I can get optimum results by stopping down 1-2 stops when using a TC. But if I'm already at ISO 1600 without the TC, should I use it and work at 3200 or 6400 (for the 2x) in order to maintain shutter speed? Should I increase ISO even more just so I can stop down to optimize image quality? In such situations other factors are coming into play that will potentially degrade image quality: high ISO noise, or if ISO isn't increased, slower shutter speeds that may not effectively freeze action, especially with a high resolution sensor. A cleaner sharp non-TC image cropped and interpolated might be better than a noisier, softer image made with a TC.
Can also depend on lens: 1.4TC is much kinder for my 500/4L IS than for 300/4L IS. I'm now upgrading from 1DMKIII to 1DMKIV and expect to use much less teleconverter, especially on 300/4. Also light plays a part: good light, possibly with same time stopped down aperture, will benefit more teleconverter.
I think it has to depend on the quality of the incoming image and its resolution, combined with the glass in the extender. Zooming in on a crummy image (one that's got resolution below that of the sensor) won't improve it, but zooming in on an image that has extra resolution will provide more detail to the sensor.... No simple answer.
Mar 13, 2010 at 01:37 AM
Lars Johnsson Offline • • • • • • • Upload & Sell: Off
it all comes down to whether your cropped image has enough resolution for your final print... I personally don't print big so if I was left with say 8MP I'd be fine...
To me the answer is autofocus. With a teleconverter the camera focuses based on a subject magnified by a teleconverter. Without a teleconverter, when cropping into an image, you better hope it was focused perfectly.
mt-m wrote:
To me the answer is autofocus. With a teleconverter the camera focuses based on a subject magnified by a teleconverter. Without a teleconverter, when cropping into an image, you better hope it was focused perfectly.
So it's
magnify, then focus
vs
focus, then magnify
Yes, but AF is significantly worse with a TC, especially 2x, so you also run a higher risk of misfocus with the converter. No free lunch.
Assuming equally good AF, I'll take the shot with a good TC over a heavily cropped shot without TC. Note that with small prints you'll probably not see any differences.
Pixel Perfect wrote:
Yes, but AF is significantly worse with a TC, especially 2x, so you also run a higher risk of misfocus with the converter. No free lunch.
Assuming equally good AF, I'll take the shot with a good TC over a heavily cropped shot without TC. Note that with small prints you'll probably not see any differences.
Nathan I think the first two have been done and reported quite a few times, and the lens vs. lens results shouldn't change with increased resolution. Should they?
The latter two, however, where you're comparing lens plus TC vs. lens plus crop — that's where I tend to believe additional resolution might come into play and change the equation somewhat.
