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Thread started 16 Jan 2018 (Tuesday) 08:05
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1.7X TC- much needed

 
John ­ Sheehy
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Jan 18, 2018 04:29 |  #46

Perfectly Frank wrote in post #18543543 (external link)
A 1.6 or 1.7 extender does interest me.

I photograph air shows using my 300 f2.8 IS II, much of the time with the 1.4xIII or 2xIII.

With the 1.4x the decrease in IQ and AF performance is nearly imperceptible.

With the 2x IQ and AF does take a hit and my keeper rate decreases, but I can still come away with some good shots.

If (and that's a big if) the 1.7x provided better IQ & AF than the 2x, then it may be a benefit for me. I'd have more FL over the 1.4x, yet still retain pretty good IQ & AF.

I agree completely on the AF part. F/8 AF is only nominal with some systems, and I think that the PDAF system is only seeing a small a mount of the incident light that it needs to see from oblique angles out of the exit pupil, demanding more contrast and/or light intensity, and operating too slow. Backing down to f/7 or so can greatly increase the needed light, without dropping to the magnification of a 1.4x.

There are many times when I use 1.4x instead of 2x because 2x causes too much hunting (birds in wildflower meadows and in trees with lots of leaves and branches behind them), and these are situations where I'd be cropping even with the 2x (or an imaginary 4x, sometimes), and the huge gap between my 1.4x and 2x kills me. That's where our opinions diverge, though; I don't believe in targeting pixel quality when using a TC. One of the main points of using a TC in my world is making sure that 100% pixel views are as soft as possible (by magnification; not TC-sourced aberration), so that I get a minimum of aliasing. I never pass on using the 2xIII because of "image quality" or "pixel quality". Loss of AF or too narrow a FOV (and possibly too dark of an OVF in very low light) are the only reasons not to use it.




  
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John ­ Sheehy
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Jan 18, 2018 04:37 |  #47

graham121 wrote in post #18543588 (external link)
I now see where you are coming from re your target audience for the 1.7x, that being the big white telephotos.

However I have to question them being the bulk of the lenses out there....surely there would be more 400F5.6, 100-400 F5.6 and 1x0-x00 glass out there than Big Whites?

Of course, any system that can be tricked to AF at f-numbers it shouldn't will have less failure with 1.7x than 2x.

Then there's live view DPAF and contrast-based live-view AF, and they also work better at 1.7x than 2x.

The gap between 1.4x and 2x is humongous. With a 20MP camera, a 1.4x simulates 40MP, a 2x simulates 80MP, and a 1.7 simulates about 58MP. When you look at it that way, the differences are not so small.




  
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CyberDyneSystems
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Jan 18, 2018 15:41 |  #48

Back when I shot 1D bodies (1.3X crop) I only used the 1.4X on occasion on my 500mm gen 1. The 2X was for "emergencies". For example, my 1st trip to Africa the T-Cons were used only on occasion. I always started the day with the bare lens and a 10MP 1.3x APS-H sensor.

This last trip to Botswana, I was shooting FF, and with the GenII IS lens and MkIII T-cons on FF, I quickly switched to starting the day with the 1.4X on, this gave me the framing I was used to after more than a decade of shooting with APS-H. The new hardware made this option far from a compromise,. they work s well together.

The 5D4 and Gen II 500mm take the T-Cons so well, I think i would really like the 1.7x. It would give me nearly the same framing I was used to with the 1.3X APS-H sensor and 1.4X T-con mounted, and of course also nearly the same as the 500mm on a 7D2/1.6 crop, the only other kind of body I was using from 2003-2015 or so when I got a 5D3.

After years of high end, high speed digital being relegated to the Crop sensor 1D series, FF framing is relatively new to me for shooting wildlife. It is at the long end where I feel less familiar,. and the T-Cons bring back a very familiar feel.


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John ­ Sheehy
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Jan 19, 2018 10:25 |  #49

CyberDyneSystems wrote in post #18543935 (external link)
The 5D4 and Gen II 500mm take the T-Cons so well, I think i would really like the 1.7x. It would give me nearly the same framing I was used to with the 1.3X APS-H sensor and 1.4X T-con mounted, and of course also nearly the same as the 500mm on a 7D2/1.6 crop, the only other kind of body I was using from 2003-2015 or so when I got a 5D3.

After years of high end, high speed digital being relegated to the Crop sensor 1D series, FF framing is relatively new to me for shooting wildlife. It is at the long end where I feel less familiar,. and the T-Cons bring back a very familiar feel.

It isn't too apparent to people who don't spend a lot of time "in the trenches" with TCs, but 1.4x vs 2x or 1.4x vs no TC are huge, coarse steps in both FOV and "pixels on subject". What I wouldn't give to have a TC with high optical quality that clicked from 1.2x to 1.4x to 1.6x to 1.8x to 2.2x, or something like that, and when I needed a narrower FOV and more pixels-on-subject, I could click to the highest magnification that gave me the minimum AF ability that I am willing to accept. As my photography paradigms become more lens-oriented, this becomes even more important, as I would like to use a given lens with a variety of FOVs and pixels-on-subject, more than I'd like to change lenses instead.




  
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Tom ­ Reichner
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Jan 19, 2018 10:35 |  #50

John Sheehy wrote in post #18544403 (external link)
What I wouldn't give to have a TC with high optical quality that clicked from 1.2x to 1.4x to 1.6x to 1.8x to 2.2x, or something like that, and when I needed a narrower FOV and more pixels-on-subject, I could click to the highest magnification that gave me the minimum AF ability that I am willing to accept. As my photography paradigms become more lens-oriented, this becomes even more important, as I would like to use a given lens with a variety of FOVs and pixels-on-subject, more than I'd like to change lenses instead.

It sounds to me like what you are describing is a zoom lens! . Except that with zooms, autofocus performance doesn't diminish as focal length increases, as it does with the use of tele-extenders.

.


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John ­ Sheehy
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Jan 19, 2018 10:53 |  #51

Tom Reichner wrote in post #18544408 (external link)
It sounds to me like what you are describing is a zoom lens! . Except that with zooms, autofocus performance doesn't diminish as focal length increases, as it does with the use of tele-extenders.

.

The difference is, zoom lenses are compromised when you zoom out, at least in aperture. The typical zoom lens has a max aperture that drops precipitously as you zoom out.

The "constant aperture" zoom is a myth. Constant "f-number" is not constant aperture; the area of the aperture in a "constant f-number" 4x zoom is 1/16 at the wide end than what it is at the long end!

A zooming TC (clickless to lock in or by any other method) does not alter aperture.

When I use telephoto zooms, I use them at full zoom mostly and just go wider to prevent unwanted cropping, which would be worse than the extra diffraction and possibly-unwanted extra DOF.




  
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Jan 19, 2018 12:49 |  #52

Don't discard the "extender" effect of a crop body (APS-C) of 1.6x as well as yet another level of extending by cropping the actual shot and getting half of it, virtually making it equivalent to 2x magnification, if the camera has plenty of megapixels. It doesn't put any additional glass between the lens and the body, doesn't affect AF performance and makes use of the center part of the lens that always performs better than the edges.




  
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Jan 20, 2018 04:05 |  #53

Sometimes a bed is too hard. Sometimes too soft. Sometimes you find one that is just right. It's always good to have 3 beds to choose from.
Some find any bed suitable and good luck to them but I think it would be wrong of them to criticise someone who wanted to try all 3 beds, it's not like they are hurting anyone.


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Jan 20, 2018 04:19 |  #54

While we are wishing for things that don't exist....I'd like a third party to make a 1.4TIS!

That's a 1.4 TC with an IS mechanism built in. (That's why I said third party, Canon won't do that)
It may not have the IS performance of the latest and greatest Canon lenses but 2 stops of IS beats none.

Any long non IS lens becomes more appealing. Sigma 420-1120 f8 IS anyone?
All the early non IS Canon super teles, Sigma 500 f4.5, 300 2.8 etc

Particularly with 77D and 80D offering f8 AF, bargain basement wildlife solutions.


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Sibil
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Jan 20, 2018 05:17 |  #55

Choderboy wrote in post #18544928 (external link)
While we are wishing for things that don't exist....I'd like a third party to make a 1.4TIS!

That's a 1.4 TC with an IS mechanism built in. (That's why I said third party, Canon won't do that)
It may not have the IS performance of the latest and greatest Canon lenses but 2 stops of IS beats none.

Any long non IS lens becomes more appealing. Sigma 420-1120 f8 IS anyone?
All the early non IS Canon super teles, Sigma 500 f4.5, 300 2.8 etc

Particularly with 77D and 80D offering f8 AF, bargain basement wildlife solutions.

I like this idea. That would be so useful.




  
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Perfectly ­ Frank
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Jan 20, 2018 07:16 |  #56

Choderboy wrote in post #18544922 (external link)
Sometimes a bed is too hard. Sometimes too soft. Sometimes you find one that is just right. It's always good to have 3 beds to choose from.
Some find any bed suitable and good luck to them but I think it would be wrong of them to criticise someone who wanted to try all 3 beds, it's not like they are hurting anyone.

Well said! :-)


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TerryWSmith
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Jan 21, 2018 10:23 |  #57

Just as an experiment - it's a bit off the topic for which I started this thread but I think worth a glance.

I experimented with stacking a couple TCs. CANON 1.4XII-Kenko PRO 30 1.4X with my 500 - 980mm F8


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Apr 07, 2018 20:58 |  #58

Looky looky what Canon has a development patent for.

http://www.canonrumors​.com …new-canon-teleconverters/ (external link)

A 1.4 & 2.0 teleconver.

Oh aaand a 1.8tc




  
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Tom ­ Reichner
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Apr 07, 2018 22:45 |  #59

CisherPhotography wrote in post #18602144 (external link)
Looky looky what Canon has a development patent for.

http://www.canonrumors​.com …new-canon-teleconverters/ (external link)

A 1.4 & 2.0 teleconver.

Oh aaand a 1.8tc

.
That's just a patent. . Canon and other manufacturers have patents on hundreds upon hundreds of things that they never intend to make. . Ever.

Before I got hopeful about something, I would have to see a heck of a lot more than a patent filing.


.


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John ­ Sheehy
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Post edited 4 months ago by John Sheehy.
     
Apr 08, 2018 08:47 |  #60

Tom Reichner wrote in post #18602192 (external link)
.
That's just a patent. . Canon and other manufacturers have patents on hundreds upon hundreds of things that they never intend to make. . Ever.

Before I got hopeful about something, I would have to see a heck of a lot more than a patent filing.

.

Still, I'd find a patent for a 1.0 to 2.8 Zoom TC pretty exciting, even if it clicked into 1/3-stop increments: 1.00 -> 1.12 -> 1.26 -> 1.41 -> 1.59 -> 1.78 -> 2.00 -> 2.24 -> 2.52 -> 2.82.

The geometry aspect of PDAF falls off of an open f-ratio cliff, almost, even when ambient light quantity is virtually unlimited, and I serious doubt that this happens in 1 stop increments between cameras, or between scene types. If your AF works snappily at f/4, but is sluggish at f/8 in good light, it may actually be almost quite as snappy at f/7.1, too, but you'd never know with the one-stop granularity upon which manufacturers seem to have an obsession. I'd pay US$1200 for such a device, if the TC-induced aberrations were low, like the 2xIII TCs.




  
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1.7X TC- much needed
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