Stacked TCs - 1.4x III + 12mm Extension Tube + 2x III

[mackguyver]

I guess I was still pretty tired from getting up so early...so sorry about the details. It was the 1D X + 1.4x III + 12mm Extension Tube + 2x III + 300 f/2.8 IS II - in that order. The technical details are: f/9, 1/320s ISO6400 +1 &1/3 EV. It was somewhat windy and the tree he was in was shaded and moving, so not really a great subject because I had to use ISO 6400, which kills some detail on it's own. Manual Focusing wasn't too hard except that the owl was moving because the tree was moving. Perfect for AI-Servo, not so great for MF!

The CA was remarkably low, pretty much non-existent between the dark branches and bright sky, and just around 1 pixel wide around the owl's eyes. What I meant by percent reductions were in comparison to the bare lens in terms of contrast (ability to resolve differences between dark & bright areas) and resolution (ability to resolve fine detail). The sensor resolution stayed the same, obviously, and the magnification increased, but not enough to overcome the additional softness, at least in my estimation. Subjectively and based on this and a couple of other trials, I would say it's like this:

300 f/2.8 IS II: Contrast: 100% Sharpness: 100%
300 f/2.8 IS II + 1.4x III: Contrast: 95% Sharpness: 95%
300 f/2.8 IS II + 2x III: Contrast: 90% Sharpness: 80%
300 f/2.8 IS II + 1.4x III + 12mm Extension Tube + 2x III: Contrast: 75% Sharpness: 50%

Maybe I'll get some test charts out and compare under controlled conditions someday, specifically to see if up-resing the 600mm files is better than the stacked extenders (I suspect it is).

It's no substitute whatsoever for a 600+1.4x or 800mm lens, but an interesting tool if you'd like to get closer to a subject and don't need super sharp files. I wouldn't use it for paid work or until I had a nice shot with the 2x, but it's fun to play with if you have the opportunity.

The necessary high ISO made this test tough, but I'll try it again if a similar situation comes up under better lighting conditions, and I'll post those results.

 

[AlanF]

What does sharpness being reduced 50% mean? Does that mean with 2x+1.4x relative to bare lens? Since adding a 2xTC can increase resolution by a maximum of x2 and a 1.4xTC by a maximum of x1.4, it doesn't look as if you are gaining anything by stacking them.

You've got a point. But remember the 2x extender increases the pixels on target by 4x. 2x in two dimensions, if that makes sense (so, say the bare lens gave you a subject 1000x1000 pixels, that would be 1MP; doubling the focal length gives you 2000x2000, which is 4MP).

It has a couple of advantages I would say. First, it makes the subject bigger in the viewfinder, which can help if you're focusing manually. Second, if you were to crop to the same size the noise patterns would be different. again it's hard to put into words. But shrinking down an image taken with a longer focal length would reduce the appearance of noise, whereas simply cropping to give the same field of view at a shorter focal length makes the noise more apparent.

In my subjective view, 2x + 1.4x does give extra resolution. Beyond that, you're not gaining any extra details, but the above points hold (the big exception being stacked astrophotography, where you regain all that resolution by combining multiple images, so any extra focal length is good).

In terms of number of pixels, sure doubling f means you get 4x more on target. However, if you halve the the resolution in 1 dimension you lose 2x2 = 4x in two dimensions. So, you have got nowhere. Now mackguyver has just found that adding the 1.4 to the 2x lowers the sharpness from 80 to 50%, ie by a factor of 1.6, for an increase in f of 1.4x. So you have actually moved back in resolution for a loss of autofocus and aperture.

 

[scyrene]

What does sharpness being reduced 50% mean? Does that mean with 2x+1.4x relative to bare lens? Since adding a 2xTC can increase resolution by a maximum of x2 and a 1.4xTC by a maximum of x1.4, it doesn't look as if you are gaining anything by stacking them.

You've got a point. But remember the 2x extender increases the pixels on target by 4x. 2x in two dimensions, if that makes sense (so, say the bare lens gave you a subject 1000x1000 pixels, that would be 1MP; doubling the focal length gives you 2000x2000, which is 4MP).

It has a couple of advantages I would say. First, it makes the subject bigger in the viewfinder, which can help if you're focusing manually. Second, if you were to crop to the same size the noise patterns would be different. again it's hard to put into words. But shrinking down an image taken with a longer focal length would reduce the appearance of noise, whereas simply cropping to give the same field of view at a shorter focal length makes the noise more apparent.

In my subjective view, 2x + 1.4x does give extra resolution. Beyond that, you're not gaining any extra details, but the above points hold (the big exception being stacked astrophotography, where you regain all that resolution by combining multiple images, so any extra focal length is good).

In terms of number of pixels, sure doubling f means you get 4x more on target. However, if you halve the the resolution in 1 dimension you lose 2x2 = 4x in two dimensions. So, you have got nowhere. Now mackguyver has just found that adding the 1.4 to the 2x lowers the sharpness from 80 to 50%, ie by a factor of 1.6, for an increase in f of 1.4x. So you have actually moved back in resolution for a loss of autofocus and aperture.

Oh, I think I interpreted '50%' differently. It's definitely something worth testing, I've never done it systematically. If I do, I'll post my results here (as I said above, my subjective impression is it's worth it up to a point).

 

[rbtree]

I finally had a suitable subject to try the stacked extenders

Great! Just skimmed this whole thread.....I've just gotten both III extenders, and want to stack, as I could do with my II units...... I'll need a Canon 12mm tube, as my off brand set of tubes won't work.

 

[mackguyver]

I finally had a suitable subject to try the stacked extenders

Great! Just skimmed this whole thread.....I've just gotten both III extenders, and want to stack, as I could do with my II units...... I'll need a Canon 12mm tube, as my off brand set of tubes won't work.

Congrats on the extenders and let us know when you get a chance to try it. I've also been thinking that my shot was probably degraded not only by the higher ISO setting but also by the humidity. It was at least 90% when I shot this - early morning, hot day, 1/4 mile from the ocean, 50yds from flooded salt flats - in Florida...and I was probably 50+ feet from the owl.

 

[applecider]

Re: Stacked TCs - 5diii + 1.4x III + 2x II + 600 f 4 ii +moon

5diii + 1.4x III + 2x II + 600 f 4 ii +moon

The "old 2x tele ii" does stack with the 1.4iii here are some moon shots from inside Portland city limits. I really like the definition the shots are adjusted for WB and contrast as well as exposure. Most are reported as F8 but must be f11, LV tried to focus but rarely did. No extension tube used.

 

[scyrene]

Re: Stacked TCs - 5diii + 1.4x III + 2x II + 600 f 4 ii +moon

5diii + 1.4x III + 2x II + 600 f 4 ii +moon

The "old 2x tele ii" does stack with the 1.4iii here are some moon shots from inside Portland city limits. I really like the definition the shots are adjusted for WB and contrast as well as exposure. Most are reported as F8 but must be f11, LV tried to focus but rarely did. No extension tube used.

Good stuff. The moon is a great target for this sort of thing. The mark II 2x will stack with any of the others afaik, as it has such a deep recess at the rear (it has to go in front of the others). The camera won't register the fact there are two - it will only recognise the TC closest to the lens, so exif for aperture and focal length will be incorrect as you've noted. I wouldn't bother with autofocus, but IS works as normal

 

[mackguyver]

Re: Stacked TCs - 5diii + 1.4x III + 2x II + 600 f 4 ii +moon

5diii + 1.4x III + 2x II + 600 f 4 ii +moon

The "old 2x tele ii" does stack with the 1.4iii here are some moon shots from inside Portland city limits. I really like the definition the shots are adjusted for WB and contrast as well as exposure. Most are reported as F8 but must be f11, LV tried to focus but rarely did. No extension tube used.

Good stuff. The moon is a great target for this sort of thing. The mark II 2x will stack with any of the others afaik, as it has such a deep recess at the rear (it has to go in front of the others). The camera won't register the fact there are two - it will only recognise the TC closest to the lens, so exif for aperture and focal length will be incorrect as you've noted. I wouldn't bother with autofocus, but IS works as normal

+1 and I've also found that AF is useless (phase and contrast AF) with the stacked TCs, but manual focus isn't as hard because of the thin DOF. Nice moon shot!