Photography Asked by renesis on December 23, 2020
My old Nikon D5000 finally bit the dust along with my grey market nikkor 70-300 lens. I am looking at replacing them both. The camera will be replaced by either the D5200 or D5300.
The lens I am looking at is the Tamaron 18-270 F/3.5-6.3 (This lens is more appealing than the 70-300 as it means I don’t have to carry two lenses while backpacking). I am fairly certain of full compatibility of this lens with whichever body I end up choosing, but maybe someone can confirm this for me?
In addition to that, I am considering purchasing a Tamron SP AF 2x Teleconverter (or other similar if there would be a better combo).
Are there any strong reasons that these would be a bad combo? I like the idea of having an extended focal length for wildlife & other far off objects, but I have read that just maybe, teleconverters used with longer focal length telephoto zoom lenses isn’t all its cracked up to be.
but I have read that just maybe, teleconverters used with longer focal length telephoto zoom lenses isn't all its cracked up to be.
Well, sort of. Not exactly. Teleconverters work best on longer focal length prime lenses. As you go shorter, generally, or if you use them on zoom instead of prime, there will be more potential issues with image quality. Below about 200mm, I personally wouldn't consider a teleconverter. Even in the "regular" telephoto range, I would not consider a 2x teleconverter at all.
Don't forget that a 2x teleconverter will incur a 2-stop penalty on your aperture, so that Tamron f/6.3 at 270mm, with a 2x teleconverter, if it will even work, will act like a f/12 520mm, but probably with noticeable softness in detail.
(See also Teleconverters 101 at the lensrental.com blog for more info. I often turn to that site for brass-tacks discussion on such things)
Another implication of the 2-stop penalty is that most APS-C cameras do not autofocus with a lens slower than f/5.6, maybe f/6.3. Thus, you will likely lose autofocus capability on that lens at just about any focal distance, with a 2x teleconverter. Even with a 1.4x teleconverter, where you lose 1 stop of aperture, assuming f/4.5 is the slowest "native" aperture that will focus with a 1.4x teleconverter, what is the focal length of the zoom when the effective max aperture is f/4.5? If that focal length is below about 200mm (270mm max focal length / 1.4x teleconverter magnification), then you won't be able to autofocus at all with any teleconverter at focal lengths that the lens couldn't already handle.
If I was going hiking with APS-C and could only carry one lens, I'd consider something like the Tamron 16-300mm f/3.5-6.3 Di II VC PZD Macro (the macro being highly beneficial if you want to stop and take a closeup pic of a flower or insect). It's got amazing zoom range; even at the wide end, it's quite wide for decent vistas of the scenery. It apparently has improved weather resistance (nice when you're hiking and it might get splashed in a sudden rain).
But I certainly wouldn't consider a teleconverter, unless you plan on taking a long fast lens. In which case, your focus probably isn't hiking.
Correct answer by scottbb on December 23, 2020
The lens I am looking at is the [Tamron] 18-270 F/3.5-6.3 ... I am fairly certain of full compatibility of this lens with whichever body I end up choosing, but maybe someone can confirm this for me?
Yes, it's compatible.
In addition to that, I am considering purchasing a Tamron SP AF 2x Teleconverter (or other similar if there would be a better combo).
Are there any strong reasons that these would be a bad combo?
Yes.
Image quality will be softer than using a 600mm lens. Of course, a 600mm lens will be a lot bigger, heavier, and expensive. The more extreme the teleconverter, the more likely there are to be image quality compromises, as with any add-on lens.
Secondly, the nature of a teleconverter is that it increases your lens's focal length. Which reduces its maximum aperture.
Remember, that the aperture f-number is defined as:
focal_length / diameter_of_opening
So, a lens of 100mm with a aperture opening diameter of 50mm is at f/2. When you add a TC, you increase the focal length, but not the size of the aperture opening in the lens. So, in this case, adding a 2x TC would give you a 200mm f/4 lens. A 2x TC adds two stops to your lens's maximum aperture.
A 2x TC would not only make your Tamron 18-270 F/3.5-6.3 into a 36-540mm lens, but also an f/7.1-f/13 lens. And the D5x00 bodies can't autofocus if the maximum aperture of the lens is smaller than f/8 (not enough light is let in by the lens wide open to focus by). This is why the basic recommendation is that 2x tcs should only be used with f/2.8 lens.
You might be able to get by with a non-reporting 3rd party 1.4x TC, which would only bring the max aperture up to f/5-f/9. But chances are good the AF performance of the lens could take a hit if you use it at the far telephoto end. Which most people do, when they get a teleconverter.
See also: "Using Teleconverters" on the nikonusa.com website.
Answered by inkista on December 23, 2020
If your focus is really just getting out to 540mm in a very small package, I would use only the lens and crop the image to achieve the desired size for your intended use. Are you satisfied with it? Great, you're done.
Not satisfied? Think long and hard about what you want. My experience with third-party teleconverters on mediocre lenses is that the results will be quite poor. DxO Mark results show the lens to be quite unsharp at the long end, and adding a teleconverter will only show that off more. This lens also shows a little pincushion distortion at the long end, and a teleconverter will also help to exaggerate that. I don't have any direct experience with this lens, but I would expect that adding a teleconverter will likely result in worse image quality than just cropping (well, depending upon your use).
Answered by Dan Wolfgang on December 23, 2020
I just got the Tamron 2x and it does not focus with the 28-270 but it works just fine with my 28-75. Manual focus will be used to get up close, no biggie.
Answered by Brad Schmid on December 23, 2020
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