DX Mode Versus Teleconverter?

[Doug Herr]

Here's a personal solution that sort of fits the original question that may also apply to at least a few others in the group who don't make their living shooting critters from a hundred of yards away every day.

FWIW, nobody makes a living from photographing critters from a hundred of yards away. Nobody. The only time a photograph of an animal made at that distance is marketable is if the animal is exceptionally rare or doing something exceptionally rare, nearly everything else is pixels-per-duck (ppd), regardless of the subject or composition. The TC increases ppd, cropping does not. Sometimes a cropped photograph still has enough ppd, thus the appeal to the professional of the high-MP bodies like the Sony a1 and Nikon Z9 along with their long lenses. Better yet increase ppd by getting closer, which is a) not alway possible and b) not always advisable. The TC is handy when getting closer is not a reasonable option and more ppd is desired.

 

[Steve]

How is this shaping up with the 600 TC Steve, compared to the FL with TC 1.4 attached? Any more noticeable delay in AF when transitioning between 600 and 840?

Honestly, I just haven't used it enough to say for sure - at least not in situations where it would be noticeable. Lately I've been shooting lots of small, close-range birds locally, and the 400 4.5 + 1.4TC is ideal for that kind of work. I do know that the 600 with it's internal TC and an extra 1.4 does suffer noticeably for action.

 

[Steve]

FWIW, nobody makes a living from photographing critters from a hundred of yards away. Nobody.

Yup, very accurate. I tell people, long glass is usually for filling the frame with small subjects - animals that you can comfortably hold in your arms or smaller

 

[Marcus]

Honestly, I just haven't used it enough to say for sure - at least not in situations where it would be noticeable. Lately I've been shooting lots of small, close-range birds locally, and the 400 4.5 + 1.4TC is ideal for that kind of work. I do know that the 600 with it's internal TC and an extra 1.4 does suffer noticeably for action.

Thanks Steve, (and without hijacking the thread too much) when you say it (AF) suffers noticeably with fast action, with the understanding it's still a new lens to you, could you elaborate a bit please? Perhaps enlarge on fast action, are you talking BIF, small fast moving birds, all of the above? I am weighing up this being my first prime lens, and there's understandably precious little detail out there yet, not withstanding you own videos of course.. so any info is really appreciated, thank you!

 

[Steve]

Thanks Steve, (and without hijacking the thread too much) when you say it (AF) suffers noticeably with fast action, with the understanding it's still a new lens to you, could you elaborate a bit please? Perhaps enlarge on fast action, are you talking BIF, small fast moving birds, all of the above? I am weighing up this being my first prime lens, and there's understandably precious little detail out there yet, not withstanding you own videos of course.. so any info is really appreciated, thank you!

It has a tougher time locking on and staying not the subject and accuracy isn't as good. When it's on, it's sharp, but it's more apt to miss critical focus than without the TC. It's not that it's unusable, it's just that you can notice a difference between using the lens with just its internal TC and using it with both the internal and external TC. This was just with things like egrets and spoonbills. However, this was also with 3.0 firmware - 3.01 might be a bit better. However, lenses without any TCs involved typically focus more reliably and accurately - especially with fast-moving targets. It's one of the reasons why I'm always advocating purchasing a lens you can use most of the time without a TC.

 

[Drbobcameraguy]

A 500 mm lens is always a 500mm lens. It does not become a 750mm lens by cropping. A teleconverter does add a magnifying element that does turn the 500 mm lens into a 700 mm lens.

When you switch to DX it is still the same lens, just cropped with exactly the same results as you would get by cropping later on the computer. Imagine viewing an 8x10 print at arms length, then getting scissors and cutting out a 4x5 print from the middle. If you still held it at arms length there obviously would be no difference since it is exactly the same print. However once you hold it closer to match the 8 x10 size or had the crop print enlarged to 8x10 you might notice the noise more and it won't seem as sharp, and it won't seem to have as much depth of field. On a screen you notice the same thing. Obviously it is the same since it is exactly the same image, until you resize it to match the full frame (or downsize the full frame to match the crop). Then you notice it is noisier, not as sharp, and not as much depth of field.

The teleconverter adds an extra glass element that magnifies the 500 mm lens, so you could say with a 1.4 for all purposes it is a 700 mm lens. The 1.4 eats one stop of light, and the extra glass can never improve the image quality of the original lens, but a good one doesn't impact it very much.

BINGO!!

 

[Maurie]

I was recently faced with a situation where I needed a longer lens than I had… z7, 100-400, 2x converter… still not enough, so flipped to DX got out to effectively 1200mm. And got the shot. Then cropped a little more to an 18mpx image

 

[NorthernFocus]

I was recently faced with a situation where I needed a longer lens than I had… z7, 100-400, 2x converter… still not enough, so flipped to DX got out to effectively 1200mm. And got the shot. Then cropped a little more to an 18mpx image.

Of course you could have simply shot in full frame mode and cropped in post for the exact same image.

 

[Maurie]

Of course you could have simply shot in full frame mode and cropped in post for the exact same image.

Agreed, but a lot easier to compose and focus when the subject filled the frame in the vf

 

[maikm]

The discussion mixes several aspects.

While a TC has optics, it doesn't actually change the focal length. It behaves like it would in most practical aspects, but what it really does is to magnify the middle part of the image while it's still in the optical path. The lens needs to have the optical reserves to deliver added detail for that to be effective, and the higher the sensor resolution, the more reserves are required.

Cropping to DX (or later in post) also magnifies the middle of the image, but after it's hit the sensor. This time, the sensor needs to have the resolution reserves for that to be effective, while not much more is asked of the lens.

So, DX crop tends to make sense if the sensor is high resolution, and TCs tend to make sense if either the sensor is lower resolution or it's a top-end prime lens anyway (with which you can obviously also combine both).

And then there are all the practical aspects, like deterioating AF performance with added TCs; what ISO you're at before adding a TC; if DX mode makes it easier or harder to frame (easier with mirrorless, harder with DSLRs; if you might miss the shot while fiddling with the converter; if you will still need to crop further anyway; if you can or need to make use of the increased buffer and reduced storage aspect with DX, and a lot more. Whole separate can of worms, and highly dependend on the specific lens and camera, so IMHO out of scope for the general question as originally asked here.

 

[Bob Hullinger]

FWIW, nobody makes a living from photographing critters from a hundred of yards away. Nobody. The only time a photograph of an animal made at that distance is marketable is if the animal is exceptionally rare or doing something exceptionally rare, nearly everything else is pixels-per-duck (ppd), regardless of the subject or composition. The TC increases ppd, cropping does not. Sometimes a cropped photograph still has enough ppd, thus the appeal to the professional of the high-MP bodies like the Sony a1 and Nikon Z9 along with their long lenses. Better yet increase ppd by getting closer, which is a) not alway possible and b) not always advisable. The TC is handy when getting closer is not a reasonable option and more ppd is desired.

It's kind of important to remember if you read much of what I write in the future that I tend to use hyperbole when making light remarks in casual conversation with no legal ramifications on the particular words I select. I think I picked a hundred yards because I was watching a football game and there were lots of photographers in the end zone. One of my first observations watching a football game is the ratio of white Canon lens to black Nikon lenses. I don't know what color SONY lenses are. My remark was obviously exaggeration. Just the same there is no harm in sharing knowledge and I appreciate it. Thanks

 

[Doug Herr]

The discussion mixes several aspects.

While a TC has optics, it doesn't actually change the focal length. It behaves like it would in most practical aspects, but what it really does is to magnify the middle part of the image while it's still in the optical path. The lens needs to have the optical reserves to deliver added detail for that to be effective, and the higher the sensor resolution, the more reserves are required.

This is veering into splitting hairs, but the combination of the lens without TC + the teleconverter is effectively a longer focal length. The effective aperture is still the entrance pupil divided by the effective focal length, extension calculations for determining magnification ratios (does anyone remember this?) use the effective focal length if the extension is between the TC and the camera body. A true telephoto lens design (vs. a long focal length design) has positive lens elements at the front and negative lens elements closer to the camera body to magnify the image, just like a TC does. The only differences are where the correction for distortion and aberrations is accomplished, and whether the negative lens group can be removed or not.

 

[Doug Herr]

It's kind of important to remember if you read much of what I write in the future that I tend to use hyperbole when making light remarks in casual conversation with no legal ramifications on the particular words I select. I think I picked a hundred yards because I was watching a football game and there were lots of photographers in the end zone. One of my first observations watching a football game is the ratio of white Canon lens to black Nikon lenses. I don't know what color SONY lenses are. My remark was obviously exaggeration. Just the same there is no harm in sharing knowledge and I appreciate it. Thanks

Understood. Long Sony GM lenses are white BTW, so the Canon/Nikon ratio can't be calculated just from the color of the lenses.

 

[Steve]

This is veering into splitting hairs, but the combination of the lens without TC + the teleconverter is effectively a longer focal length. The effective aperture is still the entrance pupil divided by the effective focal length, extension calculations for determining magnification ratios (does anyone remember this?) use the effective focal length if the extension is between the TC and the camera body. A true telephoto lens design (vs. a long focal length design) has positive lens elements at the front and negative lens elements closer to the camera body to magnify the image, just like a TC does. The only differences are where the correction for distortion and aberrations is accomplished, and whether the negative lens group can be removed or not.

I'm not an optical engineer, but that is my understanding as well. He is correct in that the TC magnifies the center area of the image, but for all intents and purposes, when a TC is attached the lens is the new focal length. Again, as I understand and apply it

 

[TonyDownunder]

And just to add to the mix, there is a lot of new, ie less than six years old, software out there that can help with dealing with higher ISO noise and image upsizing.

 

[Roy]

Good day. My question is, what are the differences between using a 1.5 teleconverter vs. dx mode?
A 500mm lens = 750mm in both incidences. Is there a good reason as to why people buy one, rather than use the DX camera mode?
I would do the experiment to find out the result(s) but I do not own a teleconverter.

The camera would only have a field of view of a 750mm lens in DX mode. DOF etc would still be the same.
A TC would lose 1 to 2 stops of light and slightly degrade the lens performance and usually AF speed.
Everything is a compromise - its good to avoid needing these drastic solutions ...

 

[bleirer]

The camera would only have a field of view of a 750mm lens in DX mode. DOF etc would still be the same.
A TC would lose 1 to 2 stops of light and slightly degrade the lens performance and usually AF speed.
Everything is a compromise - its good to avoid needing these drastic solutions ...

Again splitting hairs, but if one of the two images are resized to be equal then the DOF would also be different. For example we wish we could shoot a macro shot from farther away where the DOF is better and then crop it instead of shooting it close up where the DOF is narrow. But it's like wishing for more wishes. It doesn't work.

 

[Ivy]

Good day. My question is, what are the differences between using a 1.5 teleconverter vs. dx mode?
A 500mm lens = 750mm in both incidences. Is there a good reason as to why people buy one, rather than use the DX camera mode?
I would do the experiment to find out the result(s) but I do not own a teleconverter.

IMO comes down to choosing between losing a stop of light for a 1.4 TC and shooting at say f/8 rather than f/5.6 or giving up pixels. With high resolution cameras like a Nikon Z9 or 850, going into DX mode is faster than putting a TC on and off. But if I consistently need the extra reach, I prefer to put the TC on and keep high res shots.

 

[JoelKlein]

My 2 cents about TC’s.
Unless you could fill a frame at least halfway with the TC, AND the ISO is in check, then I will use it. Otherwise I would prefer DX. That is if I have the time to change them.
For example, In a zoo, I would take the 70-200 with the 2xTC and take it on and off as needed. Vs. shooting distance birds, and adding a TC won’t get the bird to fill at least the DX size in the frame, that means I can’t have the shot and wait for another opportunity.

The rule is: if the TC is just to take a shot which is crop-able with DX but you rather want the resolution and you have the light to support it, then go for the TC.
But, if you’re at Conowingo and the Eagles are too far away, adding a 1.4 or 2xTC on a 800pf on a gimbal, even with good light, won’t deliver the shot. I tried it and learned my lesson.

 

[Patrick M]

My 2 cents about TC’s.
Unless you could fill a frame at least halfway with the TC, AND the ISO is in check, then I will use it. Otherwise I would prefer DX. That is if I have the time to change them.
For example, In a zoo, I would take the 70-200 with the 2xTC and take it on and off as needed. Vs. shooting distance birds, and adding a TC won’t get the bird to fill at least the DX size in the frame, that means I can’t have the shot and wait for another opportunity.

The rule is: if the TC is just to take a shot which is crop-able with DX but you rather want the resolution and you have the light to support it, then go for the TC.
But, if you’re at Conowingo and the Eagles are too far away, adding a 1.4 or 2xTC on a 800pf on a gimbal, even with good light, won’t deliver the shot. I tried it and learned my lesson.

that is EXACTLY what I do too.

 

[arbitrage]

The discussion mixes several aspects.

So, DX crop tends to make sense if the sensor is high resolution, and TCs tend to make sense if either the sensor is lower resolution or it's a top-end prime lens anyway (with which you can obviously also combine both).

This is exactly my experience. I found TCs to be way more advantageous on my past 18-24MP bodies (1DX, 1DXII, A9, A9II). Especially with lower quality lenses. On my 45-61 MP bodies I much prefer to crop even with my big primes. I will sometimes still use a 1.4x on the big primes on the high MP sensor but almost never on a zoom lens like 100-400 or 200-600. But with my A9 I was happy with 1.4x on the 200-600.

 

[Hooligans Imagery]

I was recently faced with a situation where I needed a longer lens than I had… z7, 100-400, 2x converter… still not enough, so flipped to DX got out to effectively 1200mm. And got the shot. Then cropped a little more to an 18mpx image

Of course you could have simply shot in full frame mode and cropped in post for the exact same image.

Agreed, but a lot easier to compose and focus when the subject filled the frame in the vf

And you have some chance of having subject detection work better.

 

[ssheipel]

Here’s some videos on the topic:

I love how Steve seems to have a video for most every question

 

[Garfield]

I didn't watch any of the videos but will weigh-in with my experience. Leaving aside the AF issues when using a TC and only focusing on POTENTIAL IQ, given the latest high-quality generation of TCs and high-resolution mirrorless cameras and modern post-processing technology, I much prefer to use a TC than crop in camera because I'd rather collect as much pixel information as possible (i.e. full frame) to work with when post processing using the latest ISO noise reduction and sharpening software. To me, shooting in DX mode reduces the options. JMO.

In the video world where I currently play, this is clearly illustrated by the superior imagery from cameras that have the ability to oversample from FF vs. those that cannot.

 

[NorthernFocus]

And you have some chance of having subject detection work better.

That only applies to the Z9. I don't believe this topic is brand/body specific.