Pages: [1]   Go Down

Author Topic: Teleconverters less than 1.4x  (Read 3195 times)

shadowblade

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 2081
Teleconverters less than 1.4x
« on: August 08, 2017, 05:22:27 PM »

Just had a thought while discussing primes vs zooms, utility vs image quality and cropping from a prime vs using the full frame with a zoom.

The usual teleconverters available are 1.4x (1 stop) and 2x (2 stops). Nikon also produces a 1.7x version (1.5 stops). Beyond 1.4x, these tend to come with a significant tradeoff in image quality, despite magnifying the central, sharpest portion of the image circle, and are most useful when shooting action with long primes.

But what about smaller magnifications? 1.15x (0.33 stops) and 1.3x (0.67 stops), or a 1.22x (0.5 stops) TC, would carry negligible IQ penalties when used with sharp lenses and, together with a 1.4x TC, would greatly increase the versatility of primes, particularly if you don't need the rapid FL changes that a zoom provides, but want to utilise as much of the sensor area as possible rather than cropping, to maximise IQ (which is the point of using a prime in the first place). Pair 1.15, 1.3 and 1.4x TCs with a sharp prime setup and you'd end up with a kit that's sharper than a zoom setup, no heavier and with just as much focal length versatility. I could certainly envisage a setup with multiple Otus lenses and TCs being an ultimate non-action kit.

1.1-1.4x TCs already exist for projector lenses - why not photographic lenses too?
Logged

tom b

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 1322
    • http://tombrown.id.au
Re: Teleconverters less than 1.4x
« Reply #1 on: August 08, 2017, 07:36:28 PM »

Except for Glenn Bartley's excellent use of TCs for bird photography, I don't remember reading about them for a very long time. I bought a 1.4x TC for my Nikkor 105mm F4 lens around 1979, sadly recycled by theft a short time later. To be honest, except for a very small minority, most people don't know they exist or have forgotten about them.

Cheers,

NancyP

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 2199
Re: Teleconverters less than 1.4x
« Reply #2 on: August 08, 2017, 09:26:24 PM »

Whaaaat? TCs are not exactly unusual items. Even the wide angle users occasionally dip into TCs - the Canon tilt-shift 24 plus a 1.4x TC makes a much-longed-for 35mm TS lens for at least a few posters on this forum. Wildlife and sports photographers needing focal lengths above 300 to 400mm use TCs all the time. Tele-macro users prefer TCs because they are more stable than the extension tube lengths needed for longer telephotos. Teleconverters are not as common in the average snap-shot photographer's bag as in film days - simply because good-enough zooms are affordable.
One of the appeals of zooms is that you don't have to remove the lens and expose your sensor to outside elements/dust, don't have to spend the time to change lenses, etc.

One of the appeals of primes is that the limitation forces you to "work the scene" more.

Logged

shadowblade

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 2081
Re: Teleconverters less than 1.4x
« Reply #3 on: August 08, 2017, 11:29:06 PM »

Whaaaat? TCs are not exactly unusual items. Even the wide angle users occasionally dip into TCs - the Canon tilt-shift 24 plus a 1.4x TC makes a much-longed-for 35mm TS lens for at least a few posters on this forum. Wildlife and sports photographers needing focal lengths above 300 to 400mm use TCs all the time. Tele-macro users prefer TCs because they are more stable than the extension tube lengths needed for longer telephotos. Teleconverters are not as common in the average snap-shot photographer's bag as in film days - simply because good-enough zooms are affordable.
One of the appeals of zooms is that you don't have to remove the lens and expose your sensor to outside elements/dust, don't have to spend the time to change lenses, etc.

One of the appeals of primes is that the limitation forces you to "work the scene" more.

Somehow, I don't see any appeal in artificial limitations.

When shooting landscapes, I often have little choice regarding shooting distance - either you need to stand in one particular spot for features to line up, or you have no ability to change position due to geography. The required focal length is what is is - if it falls between two primes, either you use a zoom or you crop.

A few high-end, low-magnification TCs would essentially turn every prime you carry into three, greatly expanding your focal length options and reducing the need to crop.
Logged

E.J. Peiker

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 660
    • http://www.ejphoto.com
Re: Teleconverters less than 1.4x
« Reply #4 on: August 09, 2017, 01:37:04 PM »

Nikon ships their 800mm f/5.6 with a 1.2x converter to take the lens to 1000mm f/6.7
Logged

hogloff

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 291
Re: Teleconverters less than 1.4x
« Reply #5 on: August 09, 2017, 01:49:34 PM »

Somehow, I don't see any appeal in artificial limitations.

When shooting landscapes, I often have little choice regarding shooting distance - either you need to stand in one particular spot for features to line up, or you have no ability to change position due to geography. The required focal length is what is is - if it falls between two primes, either you use a zoom or you crop.

A few high-end, low-magnification TCs would essentially turn every prime you carry into three, greatly expanding your focal length options and reducing the need to crop.

Why would you want to use a TC to achieve another focal length when today's zooms deliver better quality than a prime with a TC?

I can see if you are reach limited like trying to get to 800mm, but to turn your 100mm prime into a 120mm prime by adding a 1.2 TC just doesn't do anything for me. Rather just use a zoom or switch to a 135 prime.
Logged

shadowblade

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 2081
Re: Teleconverters less than 1.4x
« Reply #6 on: August 09, 2017, 05:13:37 PM »

Why would you want to use a TC to achieve another focal length when today's zooms deliver better quality than a prime with a TC?

I can see if you are reach limited like trying to get to 800mm, but to turn your 100mm prime into a 120mm prime by adding a 1.2 TC just doesn't do anything for me. Rather just use a zoom or switch to a 135 prime.

Do they, though? Even in the corners?

I'd say that an Otus, or some Sigma Art lenses, with a TC in the 1.0-1.4x range, would be sharper in the corners and edges than any zoom at the same aperture, while also having a wider maximum aperture. It wouldn't be as versatile, in the sense of having the zoom's ability to quickly change focal length as a subject moves, but the relevant issue for non-action photography isn't that of being able to change focal lengths quickly, but of having the focal lengths available at all. For that, having a set of small, super-sharp (Otus-quality, to go with Otus lenses) TCs that would effectively triple or quadruple your arsenal of primes would be very welcome.
Logged

hogloff

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 291
Re: Teleconverters less than 1.4x
« Reply #7 on: August 09, 2017, 06:50:07 PM »

Do they, though? Even in the corners?

I'd say that an Otus, or some Sigma Art lenses, with a TC in the 1.0-1.4x range, would be sharper in the corners and edges than any zoom at the same aperture, while also having a wider maximum aperture. It wouldn't be as versatile, in the sense of having the zoom's ability to quickly change focal length as a subject moves, but the relevant issue for non-action photography isn't that of being able to change focal lengths quickly, but of having the focal lengths available at all. For that, having a set of small, super-sharp (Otus-quality, to go with Otus lenses) TCs that would effectively triple or quadruple your arsenal of primes would be very welcome.

The key here is "Otus quality" TC's. Haven't seen any yet. Every TC I've used degraded the image.
Logged

shadowblade

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 2081
Re: Teleconverters less than 1.4x
« Reply #8 on: August 10, 2017, 12:47:00 AM »

The key here is "Otus quality" TC's. Haven't seen any yet. Every TC I've used degraded the image.

A degraded image from the centre portion of a top-quality prime can still be sharper than an unmodified zoom.

After all, what's a zoom lens but a prime lens with a permanently-attached, variable teleconverter?
Logged

hogloff

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 291
Re: Teleconverters less than 1.4x
« Reply #9 on: August 10, 2017, 08:58:21 AM »

A degraded image from the centre portion of a top-quality prime can still be sharper than an unmodified zoom.

After all, what's a zoom lens but a prime lens with a permanently-attached, variable teleconverter?

Really? Good example is the Sony 12-24. It's been compared to the primes in that range and compares very favorably, quite often being sharper than great primes like the Batis 18 or even the Loxia 21. I can tell you the zoom would produce better results at 21mm than the Batis 18 with some sort of TC.

Sure older designed zooms lacked sharpness, but the latest designs really have made huge strides. Now I use primes more often than zooms for their size and weight during travel...but have zero problems bringing out a zoom when the situation warrants it.
Logged

Miles

  • Full Member
  • ***
  • Offline Offline
  • Posts: 102
Re: Teleconverters less than 1.4x
« Reply #10 on: August 10, 2017, 10:25:23 AM »

Logged

shadowblade

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 2081
Re: Teleconverters less than 1.4x
« Reply #11 on: August 10, 2017, 11:07:35 AM »

Really? Good example is the Sony 12-24. It's been compared to the primes in that range and compares very favorably, quite often being sharper than great primes like the Batis 18 or even the Loxia 21. I can tell you the zoom would produce better results at 21mm than the Batis 18 with some sort of TC.

Sure older designed zooms lacked sharpness, but the latest designs really have made huge strides. Now I use primes more often than zooms for their size and weight during travel...but have zero problems bringing out a zoom when the situation warrants it.

UWAs are a special case - prime or zoom, they all need extra optical elements, to allow for a mirror box (in SLRs) or to limit the angle of incidence of light coming onto a digital sensor. So UWAs tend to have less to gain by being made as primes.

Look at the MTFs of good standard to mid-telephoto zooms and primes. A top-tier zoom will be the equal of most consumer-grade primes, but will fall short of the best primes, particularly at the edges. This is often noticeable even when both are wide-open, and is accentuated further when the prime is stopped down to the same aperture as the zoom's maxiimum. Take the middle portion of the prime's image circle (the part that's used in the magnified image) and adjust it to cover the full sensor, even allowing for some degradation by a fixed-magnification teleconverter, and, for a sharp prime, it will often be significantly sharper in the corners than the zoom. The middle may be a bit less sharp (many top zooms do extremely well in the middle) but the edges are much sharper; for landscape photography, which requires corner-to-corner performance, that is usually preferable to a super-sharp centre with relatively weak corners.

All of which makes sense, since a zoom lens is effectively a prime lens with an attached zoom teleconverter (or zoom wide-converter, depending on the focal length range). A prime with a fixed converter attached should be sharper than a prime with an adjustable converter attached.

I use zooms for most of my shooting (when I'm not using tilt-shifts), since I want to minimise cropping to maximise resolution and image quality and, when shooting landscapes, have limited ability to choose the shooting distance (which is dictated either by geography or composition). But, if a prime with a low-magnification TC can give me a sharper result while keeping the weight of the kit to the same or less and giving me a wider maximum aperture, I'd see no reason not to prefer that.
Logged

shadowblade

  • Sr. Member
  • ****
  • Offline Offline
  • Posts: 2081
Re: Teleconverters less than 1.4x
« Reply #12 on: August 19, 2017, 08:04:02 PM »

Really? Good example is the Sony 12-24. It's been compared to the primes in that range and compares very favorably, quite often being sharper than great primes like the Batis 18 or even the Loxia 21. I can tell you the zoom would produce better results at 21mm than the Batis 18 with some sort of TC.

Sure older designed zooms lacked sharpness, but the latest designs really have made huge strides. Now I use primes more often than zooms for their size and weight during travel...but have zero problems bringing out a zoom when the situation warrants it.

For instance, take a sharp prime like the Sigma 135mm. With a 1.2x TC, it'd still be sharper than any zoom set to 162mm. Even with a 1.4x TC, it should be as sharp as the best 200mm zooms, and you'd probably have a 200mm lens in the kit as the next step up anyway. Same with a 50mm or 55mm prime - with a TC, it's still likely to be sharper than a zoom at 70mm, since that seems to be the weak ens of both 24-70mm and 70-200mm zooms (as well as an all-too-commonly required focal length for landscapes, particularly when stitching).

Three lightweight TCs with Otus-grade optics (and without protruding front bits like Canon TCs, to maximise compatibility) would go a long way towarda increasing the versatility of primes and potentially reducing the weight of a non-action-photographer's kit.
Logged
Pages: [1]   Go Up