1.7X TC- much needed

With the 5DIII and 5DIV bodies accepting tele converters so well it sure seems
like a 1.7X is needed. Bridging the gap from 1.4 to 2 would be very desirable.
I have tried aftermarkets but the quality is not there. Curious what thoughts
are or if any talks are in the works?

T.

With your 300L, the 1.7 takes it to 500. You have a 500L, so might as well just use that. But, if you add the 1.7 it takes it to 800. So, looks like you have more ability to get an 800L than a Canon 1.7 TC.

Otherwise, this sort of thing is already sort of handled with the 5DIV's resolution, and readily handled by the 5DSR's resolution, where the pixel density can be an alternative to simply needing a TC.

Very best,

MalVeauX wrote in post #18542132
With your 300L, the 1.7 takes it to 500. You have a 500L, so might as well just use that. But, if you add the 1.7 it takes it to 800. So, looks like you have more ability to get an 800L than a Canon 1.7 TC.

Otherwise, this sort of thing is already sort of handled with the 5DIV's resolution, and readily handled by the 5DSR's resolution, where the pixel density can be an alternative to simply needing a TC.

Very best,

Well aware of what it will give me in focal length- every photographer wants options and the full frame cameras
simply do not have the reach- a TC certainly helps you from having to go buy a longer lens and cropping may be an option
but I would prefer the image up front.

T.

Unfortunately a 1.7x converter would prevent the use of F5.6 lenses and limit use to F4 or faster lenses if AF is still required due to the F8 limitation on even the best of the current bodies and this alone would probably make it an uneconomical proposition.

Sorry If I read your response wrong.
But you'd be mistaken on the 800mm.

500mm with a 1.7 TC is 850mm.

I had a similar thought yesterday.

I thought a 1.6 teleconverter would be a good idea for canon.

It'd be a nice middle ground. Giving us a bit more reach as opposed to the 1.4, without losing too much light and IQ.

Anyone know where this would bring the fstop on a f2.8 or f4 lens?

F2.8= f5?
F4= f7.1?

CisherPhotography wrote in post #18542524
Sorry If I read your response wrong.
But you'd be mistaken on the 800mm.

500mm with a 1.7 TC is 850mm.

It's within engineering precision.

A 1.7x is nonsense. The whole idea of 1.4x and 2x is to increase by factors of 1.41 (approx), which is the square root of 2. If you used two 1.4x extenders, that would equal 2x. So if you are wanting a 1.7x, that suggests basing the intervals on a factor of 1.2 (approx), which is the fourth root of 2. Each step would change the aperture by 1/2 stop. The sequence would then be 1.2x, 1.4x, 1.7x, and 2x. That is splitting things too fine! As Mal pointed out, we can crop, and we can zoom.

Do we also need a 1.6x?? (just noticed CisherPhotography's post).

Maybe what we need is a zooming tele-extender!

CisherPhotography wrote in post #18542529
I had a similar thought yesterday.

I thought a 1.6 teleconverter would be a good idea for canon.

It'd be a nice middle ground. Giving us a bit more reach as opposed to the 1.4, without losing too much light and IQ.

Anyone know where this would bring the fstop on a f2.8 or f4 lens?

F2.8= f5?
F4= f7.1?

Close enough.

TerryWSmith wrote in post #18542125
With the 5DIII and 5DIV bodies accepting tele converters so well it sure seems like a 1.7X is needed. Bridging the gap from 1.4 to 2 would be very desirable.

I completely agree with you, Terry.

The reason I liked my 400 f2.8 lens so much was due to its versatility. . Use it on a 1.6 crop, a 1.3 crop, or a full frame. . Use any of those combinations with a 1.4x or a 2x extender. . That's a lot of versatility!

However, once I got my 300-800mm f5.6, I have not used the 400 f2.8 nearly as much. . Why? . Because the 300-800mm is even more versatile, and doesn't require that I switch camera bodies and fiddle with tele-extenders. . But the downside is that I am sacrificing depth of field shallowness on those occasions where shallow DOF is desirable and where I am shooting at 600mm or less.

If a 1.7 tele-extender were available, and if it performed as well as the 1.4x (no difference in image quality even when viewing at 100%), then it would breathe new life into my 400 f2.8, and I would use it much more often than I do currently.

.

MalVeauX wrote in post #18542132
. . . this sort of thing is already sort of handled with the 5DIV's resolution, and readily handled by the 5DSR's resolution, where the pixel density can be an alternative to simply needing a TC.

This resolution argument seems to say that you can just shoot a little wider than you really want to, and then just crop into the image. . But this messes with depth of field, which is so extremely important.

There are so many times when I want to get extremely picky about how much depth of field I have for a shot, and shooting wide and them cropping just throws away all of that attention to detail that I try to give my shots.

A third of a stop can actually make a big difference in how appealing a photo is, and shooting wide and then cropping in is often equivalent to giving up a significant amount of DOF - at least a third of a stop, and much more than 1/3 stop in many instances.

.

graham121 wrote in post #18542516
Unfortunately a 1.7x converter would prevent the use of F5.6 lenses and limit use to F4 or faster lenses if AF is still required due to the F8 limitation on even the best of the current bodies and this alone would probably make it an uneconomical proposition.

I'm wondering if things would just be rigged to 'report' f8, even though they would actually be at f9. . I think that this is done with the Sigma and Tamron lenses, that are f6.3 but report f5.6. So why couldn't a 1.7 tele-extender be rigged up the same way?

Lol

Tom Reichner wrote in post #18542542
I completely agree with you, Terry.

The reason I liked my 400 f2.8 lens so much was due to its versatility. . Use it on a 1.6 crop, a 1.3 crop, or a full frame. . Use any of those combinations with a 1.4x or a 2x extender. . That's a lot of versatility!

However, once I got my 300-800mm f5.6, I have not used the 400 f2.8 nearly as much. . Why? . Because the 300-800mm is even more versatile, and doesn't require that I switch camera bodies and fiddle with tele-extenders. . But the downside is that I am sacrificing depth of field shallowness on those occasions where shallow DOF is desirable and where I am shooting at 600mm or less.

If a 1.7 tele-extender were available, and if it performed as well as the 1.4x (no difference in image quality even when viewing at 100%), then it would breathe new life into my 400 f2.8, and I would use it much more often than I do currently.

.

This resolution argument seems to say that you can just shoot a little wider than you really want to, and then just crop into the image. . But this messes with depth of field, which is so extremely important.

There are so many times when I want to get extremely picky about how much depth of field I have for a shot, and shooting wide and them cropping just throws away all of that attention to detail that I try to give my shots.

A third of a stop can actually make a big difference in how appealing a photo is, and shooting wide and then cropping in is often equivalent to giving up a significant amount of DOF - at least a third of a stop, and much more than 1/3 stop in many instances.

.

I'm wondering if things would just be rigged to 'report' f8, even though they would actually be at f9. . I think that this is done with the Sigma and Tamron lenses, that are f6.3 but report f5.6. So why couldn't a 1.7 tele-extender be rigged up the same way?

Hmm - I don't think these suggestions about DOF are right.

I believe that for the same subject size, DOF depends only on aperture (keeping the sensor format the same).

Archibald wrote in post #18542569
Hmm - I don't think these suggestions about DOF are right.

I believe that for the same subject size, DOF depends only on aperture (keeping the sensor format the same).

I don't know what to say to that. . I mean, if you have been on these forums for almost 10 years, and still don't understand the impact that sensor size has on DOF, then, well ...... that's unfortunate.

Maybe this will make sense:

Shooting on a full frame sensor, and then cropping the image, is the same as shooting on a smaller sensor (all else being equal). . And we all know that the same shot with the same framing on a crop sensor has greater DOF than on a full frame sensor. . So the same thing applies to cropping in to a large image - in fact, that's why the term "crop sensor" was coined.

But this really isn't supposed to be discussion about sensor sizes - it's supposed to be about a 1.7x tele-extender. . Sorry for the detour.

.

Tom Reichner wrote in post #18542542
This resolution argument seems to say that you can just shoot a little wider than you really want to, and then just crop into the image. . But this messes with depth of field, which is so extremely important.

There are so many times when I want to get extremely picky about how much depth of field I have for a shot, and shooting wide and them cropping just throws away all of that attention to detail that I try to give my shots.

A third of a stop can actually make a big difference in how appealing a photo is, and shooting wide and then cropping in is often equivalent to giving up a significant amount of DOF - at least a third of a stop, and much more than 1/3 stop in many instances.

I think I understand what you're getting at Tom, however I think you took my comment out of context here as my comment is specific to 30~50MP sensors, where pixel density is significant and you have control over more than you would if using a smaller sensor, or a lower resolution sensor, and this approach as an alternative to a TC (especially one that does not exist).

Using a smaller sensor (changing relative field of view), and/or using a TC (increasing focal length, and slowing focal-ratio) reduce versatility if Depth of Field is your main concern. Having 50MP on a larger sensor is more versatile, if Depth of Field is of utmost importance in this application. And that is what was mentioned, referring to the 5DIV & 5DSR. You're not throwing away attention to detail, you're keeping it as an option.

Also, sensor size is not what changes depth of field. That changes field of view relative to the focal-length. Proximity (distance to subject) focus distance is what is changing depth of field, assuming focal-ratio is the same, with the relative focal length.

Very best,

Archibald wrote in post #18542535
It's within engineering precision.

A 1.7x is nonsense. The whole idea of 1.4x and 2x is to increase by factors of 1.41 (approx), which is the square root of 2. If you used two 1.4x extenders, that would equal 2x. So if you are wanting a 1.7x, that suggests basing the intervals on a factor of 1.2 (approx), which is the fourth root of 2. Each step would change the aperture by 1/2 stop. The sequence would then be 1.2x, 1.4x, 1.7x, and 2x. That is splitting things too fine! As Mal pointed out, we can crop, and we can zoom.

Do we also need a 1.6x?? (just noticed CisherPhotography's post).

Thank you so much for the condescending @$$ hat response your intelligence is amazing!!!!!!
Not sure if you thought value was being added to this thread but not even close.


T.