Teleconverters and strong zoom vs cropping

<p>When using my 500D camera with 18-135 lens I often find that even on maximum zoom objects I shoot are way close to resolution limit of my matrix, so I began to think of getting another lens. I've been looking on Tamron 70-300mm F/4.0-5.6 Di VC USD, but some people tell that there's no good in 70-300 against 70-200, because I can always crop my image and have quality good enough, thanks to large matrix resulution.<br>

<br />As I understand, the main point is the assumtion that imperfect optical quality of a lens resulting in image blurring/distorting is going sooner or later to compensate nearly all resulution benefits given by zooming itself.<br />If so, then there must be some point, depending on the camera given, when this becomes true, some zoom factor beyond which no lens is able to give any image quality improvement, I suppose?<br>

Then is there any difference between, like, Tamron 70-300mm F/4.0-5.6 Di VC USD and Canon EF-S 55-250mm f/4-5/6 IS from that point of view?<br>

Also, are 2x teleconverters under $150 worth considering for that purpose? If so, what exactly could I use?</p>

<p>Thanks in advance!</p>

<p>There is no substitute for a good long focal length lens on any given camera. The factors involved in getting a good quality image are numerous and include the lens itself to the person taking the shot. Longer focal length lenses require the lens to be held a steady as possible and to have the highest shutter speed as possible.<br>

Image stabilization helps as does a fast lens, both of these come at a cost.<br>

Putting convertors in a long lens will give a better focal length but at the expense of more glass and a slower lens.<br>

There is possibly a image quality relationship between increasing the focal length by zooming vs cropping, but I should imagine it depends on the lens. I am sure there are those who can give the merits of one lens compared to another but in the end it will come down to one of cost.</p>

<p>The logic is somewhat erroneous. The bottom line is that with an appropriate focal length, you will be able to acquire a final image that is substantially better than one shot with too short a FL, and cropped down.</p>

<p>Of course to what degree the first image is superior will depend considerably on a) what you are shooting, b) the camera you are using, c) the specific lens combination you are using, and d) what kind of output you need. Regardless of just how much superior the first image is, it will almost always <em>be</em> superior in quality.</p>

<p>Then there is the matter of focus accuracy, and exposure accuracy. If you are tightly zoomed on your subject this is rarely a problem, however, the wider your initial shot, the greater the chance the camera will miss focus (sometimes only slightly), or mis expose your image (exposing for, say, the background). Both will substantially decrease your final image's IQ.</p>

<p><em>"Then is there any difference between, like, Tamron 70-300mm F/4.0-5.6 Di VC USD and Canon EF-S 55-250mm f/4-5/6 IS from that point of view?"</em><br>

Yes. But in part simply because the Tamron produces slightly better IQ. That, in addition to the increased FL, makes a substantial difference in the output.</p>

<p>As far as the cost effectiveness of a cheap 2x teleconverter? Yes, they are almost always worth it (when considered without comparing them to higher quality units). They vary in quality, but almost universally will produce a better (though sometimes only slightly) final product than the same lens (without the TC mounted) cropped to half the image size. However, If you lose AF, and cannot MF to satisfaction, then all that goes out the window though.<br>

As far as the differences between a sub $150 one and a Canon 2x mkIII TC (which is only usable with some lenses)? That is far more ambiguos. I don't (and never have) used the Canon's, and only rarely use the 'off brand' units so I can't do a comparison between the two. </p>

<p>The true answer to your question is "It depends". It depends on the lens and it depends on the multiplier ins use. Sometimes cropping may be better, sometimes the multiplier may be better.</p>

<p>With really good lenses (usually primes and expensive zooms) and good multipliers, the multiplier is always better. Good multipliers are the ones made by the camera manufacturers and the better 3rd party manufacturers like Tamron and Sigma. If a multiplier has a name you don't recognize and/or costs under $100, it's unlikely to be good.</p>

<p>I have some actual sample comparison shots at <a href="http://www.bobatkins.com/photography/tutorials/tc3.html">http://www.bobatkins.com/photography/tutorials/tc3.html</a></p>

<p>I use TCs <em>a lot</em>, and - <strong><em>with the right lens</em></strong> - even a 2x TC can give excellent results.</p>

<p>These for example are all Sigma 120-300mm f/2.8 OS + 2x Sigma TC on a Canon 7D at 600mm, handheld. Nothing much wrong with these:</p>

<p>http://www.capture-the-moment.co.uk/tp/tfu29/upload/600mm_sigma/canada_goose_marden_1.jpg<br>

http://www.capture-the-moment.co.uk/tp/tfu29/upload/600mm_sigma/greylag_marden_3.jpg<br>

http://www.capture-the-moment.co.uk/tp/tfu29/upload/600mm_sigma/greylag_marden_1.jpg<br>

(<a href="http://www.kazemisu.me.uk/images/croft_1200_10a.jpg">link)</a><br>

<a href="http://www.capture-the-moment.co.uk/tp/tfu29/upload/600mm_sigma/600mm_7.jpg">(link)</a><br>

http://www.capture-the-moment.co.uk/tp/tfu29/upload/260912/house_sparrow_st_marys_3.jpg</p>

<p> </p>

<p>True, 2x TCs on the right lens are fine, but the OP is asking about sub $400 consumer zooms.</p>

<p>In fact the Tamron 70-300 VC works OK with a Tamron 1.4x TC. You can even get AF with Canon EOS DSLRs using live view and contrast detection based focusing.</p>

<p>See <a href="http://www.bobatkins.com/photography/technical/TC_contrast_detection_AF.html">http://www.bobatkins.com/photography/technical/TC_contrast_detection_AF.html</a> for a few examples of this combination.</p>

<p>I would not put a 2x TC on any low cost (sub $500) consumer telephoto zoom. You might get away with it on the Canon EF 70-200/4L, but I'm not sure it would be any better than a 1.4x on the Tamron 70-300 (which also has stabilization and costs significantly less).</p>

<p>I suppose results can vary, depending on the lens and the TC. Not wanting to invest in expensive long glass, but still wanting to play at a bit of bird photography, I bought a Takumar 500mm f/4 lens, which is quite cheap and relatively OK, and I put it on a fairly good Komura 2x TC. I found that the 500 and the TC together gave me better resolution than a cropped image, by far. It becomes a very slow combination, when you consider I have to stop down the lens a bit to reign in some of the lens' chromatic aberration. However, focusing with 10x liveview takes away all the pain.</p>

<p>BTW, for Canon shooters, B&H is selling the EF 2.0X TC-III for $429, including shipping.</p>

<p>Until recently I owned that Tamron 70-300. The image quality was average but the lens is on the fragile side. I dropped it and the internals broke in multiple places.</p>

<p> </p>

 

<blockquote>

<p>The true answer to your question is "It depends". It depends on the lens and it depends on the multiplier ins use. . . <em><strong>With really good lenses (usually primes and expensive zooms) and good multipliers, the multiplier is always better.</strong></em></p>

</blockquote>

<p><a href="/photodb/folder?folder_id=978596">Another Example - here.</a></p>

<p>WW</p>

<p>@Keith Reeder:</p>

 

<blockquote>

<p>These for example are all Sigma 120-300mm f/2.8 OS + 2x Sigma TC on a Canon 7D at 600mm, handheld.</p>

</blockquote>

<p>Birds are extremely beautiful!<br>

On the photo with a bike performing a turn, has the background seen some postprocessing, or is it just optical blurring?</p>

<p>Hello, Vsevolod,</p>

<p>thanks for the kind words.</p>

<p>The background of the bike picture is heat haze coming out of the bikes' exhausts - "jelly air" as it's called in aircraft photography circles - which I've processed (by gentle <em>sharpening</em>, not blurring) to enhance and make more obvious.</p>

<p>@Keith Reeder:</p>

 

<blockquote>

<p>bikes' exhausts - "jelly air"</p>

</blockquote>

<p>Yes, that idea had crossed my mind, but when I was writing a reply just "blurring" came out.<br>

Great quality, guess my 500D wouldn't do that good, but still I think it is capable of far more than I've managed to use.</p>

<blockquote>

<p>but still I think it is capable of far more than I've managed to use.</p>

 

</blockquote>

<p>That's an excellent attitude, Vsevolod - true of most of us, as well: it's rarely the case that the <em>equipment</em> is the weak link!</p>