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Author Topic: TC or Crop? Is there a consensus? Please help!  (Read 7817 times)

canon816

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #15 on: August 13, 2012, 01:24:38 PM »
There is no consensus on this whatsoever.

There are some very strong opinions though.

Here is mine: 
It really depends on the TC and the lens you would use it on.  Not only that, it depends on specific copies of TC's.  I AFMA calibrate all my lenses to my bodies so my conclusions are based on actual IQ.

I have done a ton of IQ testing with TCs and lenses with focal which quantitatively allow you to compare.  I have also extensively used TC's in the field and have established what works and doesn't work well... for me.

I have found that Canon's 2.0x TC is junk.  I have used 3 copies of my own and borrowed several as well.  I never get sharp images on any lens.  No matter what lens I use with a 2X i can achieve better results shooting without it and cropping in post processing.  I will not use a 2x TC on any lens and have   (Especially with the hit it puts on the AF responsiveness)

Regarding the 1.4x.  I have a decent copy of this (ver II) and use it all the time.  I use it on my 70-200f4 and on my 300f2.8.  I DO NOT use it on my 600f4.  Again, it degrades the image quality enough on this lens that I can crop an image in post and end up with a higher quality image then when using the 1.4x for the optical advantage.

If you are going to use TC's it really comes down to how much image quality you are willing to sacrifice.  I have seen an image shot by George Lepp with a 600f4 + 2.0x+ 1.4x that was manually focused and it looked really great.  Whatever you decide to do I would advise that you stick with Canon brand.  The third party TCs are really poor.  You can always rent a couple and try them for yourself to see what they do for you.  I know a lot of photographers who have an apetite for slightly soft images... I do not.  I want razor sharp, and for me I am very critical on what TC I will use and on what lens. 

Good luck!

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #15 on: August 13, 2012, 01:24:38 PM »

Mt Spokane Photography

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #16 on: August 13, 2012, 01:32:45 PM »
Here are some images of Mount Spokane from my back deck for a comparison of my 100-400mmL at 400mm with 1D MK III and Canon TC mk II's.  I've cropped them all to the same view.  With no TC, thats 100% so the image is smaller. They have no post processing other than my lightroom defaults, so obviously they can be improved.

I feel that the 1.4X TC provided the best image, I tried to avoid any motion and used a heavy tripod with underweight, however, with the long TC's, there may have been some vibration, particularly with the 2X.  The top of the mountain is several miles away, so there is a lot of distortion coming from 7 miles of air.

Nice comparison. Could you also post the f-stops used or do you have a stopped down image of the 2x? In my experience the 2x "wide open" doesn't work very well.

Also i have the 2nd hand impression that there are old and new 100-400mm lenses which perform differently. So if you have an old one it wouldn't work as well.
The lens is fairly new, I love it.  These are difficult shots due to the distance.
Reported Settings.  These are what is recorded in EXIF and, in the case of stacked TC's the f stop is wrong.  I used AV setting of f/11, but the aperture of the lens would have varied according to the TC with it being stopped down more without a TC
Also, it was a winter day and the light varied from shot to shot so the shutter speeds varied according to available light.
No TC  - 1/2500 sec f/11, ISO 800
1.4X - 1/3200 sec f/11 ISO 800
2X   - 1/3200 sec f/11 ISO 800
1.4 + 2X - 1/2000 sec f/11 ISO 800 (not the actual equivalent aperture)
It might be interesting to redo them with my 1D MK IV, but in our near 100 degree weather, the air is too turbulent, and the 1D MK IV is going to be sold soon.
 

R1-7D

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #17 on: August 13, 2012, 02:13:10 PM »
Here's a nice little video showing a comparison with and without a teleconverter.

http://digitalphotocentral.com/2011/canon-teleconverter-or-extender-test/
Cameras: 1DX, Canon M. Lenses: Canon EF 24-70mm f/2.8L II, Canon EF 70-200 f/2.8L IS II,  Canon EF 100mm f/2.8L Macro, Canon EF 2X III, Tokina SD 16-28mm f/2.8 FX, Canon M 18-55mm IS, Canon M 22mm. Flashes MT-24 580EXII

epsiloneri

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #18 on: August 14, 2012, 02:01:46 AM »
You can only win here if you increase the exposure time. In total you have more noise compared to cropping or using a camera with smaller pixels, but you also have more photons if you increase the exposure time to overcompensate for that and increase DR and SNR after downscaling.
Yes, you got it right. The point is that you don't lose (much) light by using a TC, compared to cropping. Yes, the absolute noise increases, but the relative noise (noise relative to the signal) decreases as sqrt(number of photons), if photon dominated. To say that the noise increases can be confusing, since it gives the impression that to get the lowest noise images, you expose for as short time as possible. Ideally, a completely dark image has zero photon noise  ;)


heptagon

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #19 on: August 14, 2012, 02:50:58 AM »
The lens is fairly new, I love it.  These are difficult shots due to the distance.
Reported Settings.  These are what is recorded in EXIF and, in the case of stacked TC's the f stop is wrong.  I used AV setting of f/11, but the aperture of the lens would have varied according to the TC with it being stopped down more without a TC
Also, it was a winter day and the light varied from shot to shot so the shutter speeds varied according to available light.
No TC  - 1/2500 sec f/11, ISO 800
1.4X - 1/3200 sec f/11 ISO 800
2X   - 1/3200 sec f/11 ISO 800
1.4 + 2X - 1/2000 sec f/11 ISO 800 (not the actual equivalent aperture)
It might be interesting to redo them with my 1D MK IV, but in our near 100 degree weather, the air is too turbulent, and the 1D MK IV is going to be sold soon.

Another thing is: Did you scale the images made with the TC or change the focal length? Comparing the length of the tower by hand doesn't give a magnification of 2x or 2.8x compared to the 1.4x (maybe this is also done on the webpage). I ask this because scaling images is also often problematic and there is quite some discussion on how you should scale the images in order to provide a "fair" comparison.

What we can conclude however is that taking images with a TC is much more complicated than using the bare lens.

heptagon

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #20 on: August 14, 2012, 02:57:06 AM »
If needed i use the 2x iii which gives amazing results in good light and for slow moving subjects. With the 2x 8x more shutter time is needed, 4x because of 2 stops less opening and 2x stop because of doubled focal lenght. from my experiance its better to cop a picture than pushing up iso by 3 stops, as iso 1600 looses lots of detail compared with iso 200 on the crop body.

For the 70-200 L IS II you could add another stop to the light requirement for stopping down from f/5.6 to f/8 with extender instead of useable f/2.8 without extender. So that would be 16x more light required. However there might just be enough light for all directly sun-lit subjects. If you can shoot at f/16 without extender, you can shoot at f/8 with extender.

hendrik-sg

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #21 on: August 14, 2012, 03:22:59 AM »

For the 70-200 L IS II you could add another stop to the light requirement for stopping down from f/5.6 to f/8 with extender instead of useable f/2.8 without extender. So that would be 16x more light required. However there might just be enough light for all directly sun-lit subjects. If you can shoot at f/16 without extender, you can shoot at f/8 with extender.
[/quote]

You are right, stopping down  stop may improve the image quality. The 70-200 ii i dont know, but with the 300 2.8 i nearly never had lighting conditions where i get an improvement by stopping down, as motion blur is worse than "lens softness" or "converter softness".

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #21 on: August 14, 2012, 03:22:59 AM »

Mt Spokane Photography

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #22 on: August 14, 2012, 12:25:26 PM »
The lens is fairly new, I love it.  These are difficult shots due to the distance.
Reported Settings.  These are what is recorded in EXIF and, in the case of stacked TC's the f stop is wrong.  I used AV setting of f/11, but the aperture of the lens would have varied according to the TC with it being stopped down more without a TC
Also, it was a winter day and the light varied from shot to shot so the shutter speeds varied according to available light.
No TC  - 1/2500 sec f/11, ISO 800
1.4X - 1/3200 sec f/11 ISO 800
2X   - 1/3200 sec f/11 ISO 800
1.4 + 2X - 1/2000 sec f/11 ISO 800 (not the actual equivalent aperture)
It might be interesting to redo them with my 1D MK IV, but in our near 100 degree weather, the air is too turbulent, and the 1D MK IV is going to be sold soon.

Another thing is: Did you scale the images made with the TC or change the focal length? Comparing the length of the tower by hand doesn't give a magnification of 2x or 2.8x compared to the 1.4x (maybe this is also done on the webpage). I ask this because scaling images is also often problematic and there is quite some discussion on how you should scale the images in order to provide a "fair" comparison.

What we can conclude however is that taking images with a TC is much more complicated than using the bare lens.
They are crops, so  the scaling cannot be measured when you crop a image.  As noted, I cropped them to show the tower at about the same height, except that the no TC crop resulted in a 100% crop so it is a little smaller.  If the objective is to see which combination produces the most detail of a distant object, a crop works best.
Full images are linked below to avoid taking up bandwidth for users.
No TC
http://www.mount-spokane-photography.com/Photography/100-400mm-L/400mm-no-tc-2603/1179530174_evXBt-X3.jpg
1.4X
http://www.mount-spokane-photography.com/Photography/100-400mm-L/400mm-14X-2600/1179529520_E4yYv-X3.jpg
2X
http://www.mount-spokane-photography.com/Photography/100-400mm-L/400mm-2X/1179528230_FVjWy-X3.jpg
1.4X + 2X
http://www.mount-spokane-photography.com/Photography/100-400mm-L/400mm-2X-14X/1179528853_BdbVA-X3.jpg
 
A 50mm shot for comparison. Try scaling it :)
 

 
 
 
 

heptagon

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #23 on: August 14, 2012, 12:38:13 PM »
You are right, stopping down  stop may improve the image quality. The 70-200 ii i dont know, but with the 300 2.8 i nearly never had lighting conditions where i get an improvement by stopping down, as motion blur is worse than "lens softness" or "converter softness".

The 70-200 II with 2x extender just doesn't look right at F/5.6 at F/8 there is a big improvement. It's about on the sharpness level of the 400 L F/5.6 when shooting between F/5.6 and F/8.

As far as i know the 300 F/2.8 is already a very sharp lens wide open. But it's hard to actually find the reason for softness at long focal ranges as focusing problems and various vibration sources also play a role.

For me a subject in direct sunlight and the lens on a monopod with IS on and the camera (550D) on iso 400 max worked pretty well but only half of the shots are satisfying. Selecting a higher iso destroys detail and you cannot sharpen the image anymore without adding a lot of grain. So the situations where using a TC actually makes sense are pretty limited.

heptagon

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #24 on: August 14, 2012, 12:52:15 PM »
You linked to scaled versions of the images but i found the originals in your gallery  :)

It's pretty hard come to a definite conclusion regarding the quality. Also at the shot with the 2x converter a cloud is on the main tower reducing contrast and it seems like some kind of noise reduction is employed. Additionally there may be air turbulences and slight focusing errors etc.

I think most people will be happy with the 1.4x extender on any tele lens F/4 or faster but the 2x extender is only a compromise.

A 50mm shot for comparison. Try scaling it :)
 

That's quite impressive!


Mt Spokane Photography

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #25 on: August 14, 2012, 01:16:13 PM »
You linked to scaled versions of the images but i found the originals in your gallery  :)

It's pretty hard come to a definite conclusion regarding the quality. Also at the shot with the 2x converter a cloud is on the main tower reducing contrast and it seems like some kind of noise reduction is employed. Additionally there may be air turbulences and slight focusing errors etc.

I think most people will be happy with the 1.4x extender on any tele lens F/4 or faster but the 2x extender is only a compromise.

A 50mm shot for comparison. Try scaling it :)
 

That's quite impressive!
Yes, there are flaws in the test, a distant object miles away is not really the best type of test, that pesky air, clouds, water vapor, etc change all the time.  Also, from a wooden deck, someone walking in the house might affect it.

Its pretty clear that a 1.4X does a good job with a 10mp 1D MK III.  The result with a 18mp 7D might be different, I might setup on concrete one day and try that.  I now have a laptop holder on my tripod, or can use a long USB cable and focus / capture remotely to get the best possible image.  However, something closer might be better.

I really do not use my 100-400mm L with TC's, its too much of a bother for any possible gain.  I can crop most of the time, and other issues usually out prioritize using a TC.

Here is a cropped image of a female redwing blackbird as she dropped from our crabapple tree to the ground to pickup sunflower seeds. I loved the way I could AF on the bird right thru the clutter of the tree with my 5D MK II.  I always was wondering at those who could not AF with it. 100-400mm with no TC.
 

« Last Edit: August 14, 2012, 01:47:58 PM by Mt Spokane Photography »

Skulker

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #26 on: August 14, 2012, 01:34:01 PM »
If its occasional wildlife I would crop, basically for the reasons given above. But mainly because I find that putting the 100-400 on a 2XTC is pushing it a bit on the 7D as far as IQ is concerned. And of course there is the AF issue, ie it wont.

This makes me think I must try the TC's and the 100-400 on the full frame.


EDIT
Having tried it, its a pain not having AF, my type of shooting tends to want a quick shot.
« Last Edit: August 15, 2012, 12:28:10 PM by Skulker »
If you debate with a fool onlookers can find it VERY difficult to tell the difference.

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #26 on: August 14, 2012, 01:34:01 PM »