Please, make me smarter. 1.4x TC built in lens vs. crop option in camera

[climber]

Ok, first of all, I'm asking that just out of curiosity and want to know what is the difference.

1. case: FF body with Canon's 200-400/4 lens with 1.4x TC. You are able to extend focal length with one switch.

2. case: FF body with option to switch to crop mode. (to make things simpler, let say crop factor is 1.4) Lens in that case is 200-400mm/4 - with no built-in TC.

I'd like to know what are pros and cons of each approach? In 1. case you lose 1 stop when switch TC on. From f/4 to f/5.6.

In 2. case, the aperture stays the same - f/4 (at least I think so) So, what are cons here?

 

[Random Orbits]

Imagewise, case 2 is no different than taking the picture without using the crop mode and then cropping to the same FOV in post (and losing MP). The advantage to doing it in-camera is that files are smaller. Case 2 also does not change the focal length.

Case 1 changes the focal length and the max aperture, which affect depth of field and exposure. The advantage of a TC is that you get to use all the camera's MP rather than throwing away a significant fraction of them by "cropping" in camera. A good lens with a good TC will easily outresolve case 2.

 

[Sella174]

Hey, "Option 2" just gave me an idea: a FF sensor with a higher photosite density in the centre (equivalent in size to an APS-C sensor); kind of like an 18MP sensor inside an 18MP sensor.

So what's the benefit? The ability to use both EF and EF-S lenses at same MP count; and more "resolution" for higher sharpness in the central part of the FF image.

Crazy nutty idea, huh?

 

[privatebydesign]

Hey, "Option 2" just gave me an idea: a FF sensor with a higher photosite density in the centre (equivalent in size to an APS-C sensor); kind of like an 18MP sensor inside an 18MP sensor.

So what's the benefit? The ability to use both EF and EF-S lenses at same MP count; and more "resolution" for higher sharpness in the central part of the FF image.

Crazy nutty idea, huh?

Yes, because EF-S lenses can't clear the mirror of FF cameras, so you'd have to have a third, fourth sixth EF lens designation after EF, EF-s, EF-M, TS-E, MP-E.

Oh and the more pixels from a crop don't actually translate to any more resolution in real world shooting from same generation sensors anyway. So all in all it is a bad idea that won't work.

It's only real niche is for manufacturers that really messed up their lens strategy and stated, very boldly, they would never make a ff digital sensor as there was no need, but then after selling a good amount of crop digital only lenses realising they were talking crap and had to release a ff digital sensor. Hence lens confusion, compatibility nightmare, and all around dissatisfaction. On the other hand you can use your $150 lens on your $3,000 camera.

 

[privatebydesign]

Ok, first of all, I'm asking that just out of curiosity and want to know what is the difference.

1. case: FF body with Canon's 200-400/4 lens with 1.4x TC. You are able to extend focal length with one switch.

2. case: FF body with option to switch to crop mode. (to make things simpler, let say crop factor is 1.4) Lens in that case is 200-400mm/4 - with no built-in TC.

I'd like to know what are pros and cons of each approach? In 1. case you lose 1 stop when switch TC on. From f/4 to f/5.6.

In 2. case, the aperture stays the same - f/4 (at least I think so) So, what are cons here?

The cons are equivalence, cropping has a focal length factor, as we all know, what seems to be missed too often is it also has an aperture and iso factor. Your FF 560mm f5.6 at 1/500 sec and 400iso, is equivalent to the crop of 400 f4 at 1/500 sec and 200iso, but in reality the ff shot will have less noise and lots more pixels. The ff image will have around 1 stop IQ advantage, the pictures will have identical dof, and exposure when reproduced at the same size on screen or in print.

In this specific situation there is no advantage to going the crop route.

There are advantages to using a crop camera, not a crop mode, not least cost, a 7D with a 400 f5.6 is very very close to a 1Dx with a 600 f4, but there are over two stops difference in IQ, even if you crop the 1DX a bit to get the 640mm. Also framing with a crop camera can be much easier if the subject is smaller, but that isn't the case in your hypothetical.

 

[Sella174]

Yes, because EF-S lenses can't clear the mirror of FF cameras ...

I know this is blasphemy, but ... just chuck the mirror.

So all in all it is a bad idea that won't work.

Crazy/nutty/silly ideas = bad ideas. Now we all know. :-X

 

[climber]

Great, thanks guys.

 

[tolusina]

....
2. case: FF body with option to switch to crop mode.......

In point and shoot terms, that's 'digital zoom' and rather useless. You can get the identical effect by cropping in post.
Also, if you set crop mode in camera, in the heat of action, you may overlook setting it to off and lose a lot in subsequent shots.

Hmm, don't know this one, is crop mode shown in the viewfinder, maybe with projected crop lines or only in live view?
If crop doesn't show in the viewfinder, what you see through the viewfinder will be substantially more that what you actually get, that sounds highly undesirable to me.
If crop lines do show in the finder, seems like something else diverting your attention from the primary task.




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[9VIII]

In all the discussions and examples I've seen, optical magnification is always superior. What it may not be is inexpensive or conveniant.