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Author Topic: TC or Crop? Is there a consensus? Please help!  (Read 7789 times)

fugu82

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TC or Crop? Is there a consensus? Please help!
« on: August 13, 2012, 12:20:50 AM »
I have been trying to decide whether to purchase a Kenko 1.4 or 2.0 teleconverter for my 5D3, and after a fair amount of research, cannot find a definitive, objective answer to the TC or crop question. So, someone out there, is it worth the $$ and the manual-focus PITA to use a TC on my 100-400 for my [occasional] wildlife shoots, or is the final image-quality roughly equivalent to a crop? Thanx in advance.

Kathode-Ray

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #1 on: August 13, 2012, 02:25:17 AM »
Hi,

I did a test once with my 70-200 4.0 L IS and a Canon EF 1.4x II converter. At 200mm, the image quality cropped (to approx. the same field of view) was better than the one with the converter. So no converter for me :)

Ray
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heptagon

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #2 on: August 13, 2012, 02:58:04 AM »
1: your lens needs to outresolve the sensor at the longest focal range. If it doesn't you won't gain anything.

2: you lose f-stops if you put on the TC. (The light gets distributed on an area 2 or 4 times as big, leading to 1 or 2 f-stops loss of light density on the sensor.)

3: Your lens needs to be wide enough to still reach f/5.6 for autofocus. (Autofocus also gets slower with extender due to less light on the focusing mechanism. Low light performance is worse.)

4: you may want to stop down further to f/8 because that usually improves the image quality and resolution.

5: you may need a tripod because 800 mm focal length are hard to hand-hold.

Since you write about the 100-400mm lens on a 22MP FF-body, i assume that it would go well with the 1.4x extender since then the resolution matches a crop body with 18MP without extender. The 2x extender would most likely result in blurred images which don't provide more detail. Also the overall image quality reduces severely with 2x extenders. It's not just resolution but also contrast CA vignetting distortion etc.

What you could try is to use MF and shoot at F/8 without extender and if you can work with that, go for the 1.4x extender (or better yet get a used crop body, which equals to about 1.5x extension but with working AF and no f-stop loss).

EDIT: I may have misunderstood you. Decreasing the sensor size is always better than a TC. So a crop body with all other things equal will always be better. Unfortunately you also have to consider price, weight, different performance of different bodies, different noise characteristics etc... I for myself use a crop body + TC.
« Last Edit: August 13, 2012, 03:07:35 AM by heptagon »

heptagon

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #3 on: August 13, 2012, 03:04:44 AM »
Hi,

I did a test once with my 70-200 4.0 L IS and a Canon EF 1.4x II converter. At 200mm, the image quality cropped (to approx. the same field of view) was better than the one with the converter. So no converter for me :)

Ray
Did you stop down to f/8 for taking the images? I have a 2x III extender on a 70-200mm L IS II and it is ok (not great but ok) when stepped down. However with increased focal length the exposure time also has to be shorter in order to avoid blur due to shake or movement of the object.

I heard a lot of diverging impressions from people using extenders. You definitely lose resolution and contrast when zoomed to 100% but you still usually gain in detail of a small subject and if you can't carry an additional long lens, the extender is better than cropping. Maybe the differing impressions are from people not adjusting for the longer focal length or due to manufacturing variations of the lenses which become obvious with the additional magnification.

epsiloneri

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #4 on: August 13, 2012, 05:06:21 AM »
2: you lose f-stops if you put on the TC. (The light gets distributed on an area 2 or 4 times as big, leading to 1 or 2 f-stops loss of light density on the sensor.)
Light density, yes, but not total light, so it's not so bad. For this reason, you can improve signal to noise and dynamic range with a TC compared to cropping since you can collect more photons from the same scene without saturating. (you could of course also take multiple exposures with the same result with the crop)

 

hendrik-sg

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #5 on: August 13, 2012, 05:22:09 AM »
I examined this qestions with a 300 2.8 is I and and 2x III with a 50d and a 5dii

best is as expected 5d + bare lens.

Next step is using the 50d on bare lens for two reasons. the 50d has the better autofocus than 5dii and i retain the 2.8 opening. Yes i know the iso performance is worse than with the 5dii about one stop.

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.

So my conclusion is that the converter gains some resolution, at least with this fantastic lens, but only in excellent lihting conditions and with slow moving subjects. In challenging conditions, cropping is favourable

M.ST

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #6 on: August 13, 2012, 05:50:32 AM »
If have both TC´s. But if you want to use a FF camera with the 1.4X III TC, better use a additional APS-C  body for the best image quality. I often use an APS-C body instead of the 1.4X III TC.

No TC can reach the image quality of a DSLR.

Menace

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #7 on: August 13, 2012, 06:22:35 AM »
I recently sold my 7d and moved to 5dIII. I do miss the reach occasionally so (for my needs) I'll either get a refurb 7d or an xxD body rather than TC.

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Ayelike

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #8 on: August 13, 2012, 08:32:42 AM »
I too sold my crop for a FF (5D3) and now I want to buy a crop as a second camera. Thinking about a 7D.

Before I do that though, I'm going to hire an extender for my 70-200mm f/2.8. These hire pretty cheap (in the UK at least). I'm going to get one for a weekend at just £10 then I can try out resolution and focus speed and tracking for myself.

I think renting one is the only way you're really going to know if it meets your needs for sure.


Lnguyen1203

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #9 on: August 13, 2012, 09:45:18 AM »
The 100-400 is not that sharp at 400mm, so adding TCs and losing 1 or 2 stops will hurt.  But I have seen people claiming that the 100-400 with the Kenko 1.4x is very useable in good light.  You just need to check it out yourself I guess.
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neuroanatomist

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #10 on: August 13, 2012, 10:32:07 AM »
Depends on the lens being used.  For example, with the 100-400mm, I'd say you're better off using an APS-C body or cropping the resulting images than trying to use a 1.4x or 2x TC.  But, with a MkII supertele prime, you'll get better IQ from a FF camera combined with a 1.4x III extender than with a 7D.
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fugu82

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #11 on: August 13, 2012, 12:08:55 PM »
Thanx, all. Looks like I will be doing some cropping.

Mt Spokane Photography

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #12 on: August 13, 2012, 12:48:33 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.

No TC

 
1.4X

 
2X

 
1.4X + 2X

 
« Last Edit: August 13, 2012, 12:52:25 PM by Mt Spokane Photography »

heptagon

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #13 on: August 13, 2012, 01:01:02 PM »
2: you lose f-stops if you put on the TC. (The light gets distributed on an area 2 or 4 times as big, leading to 1 or 2 f-stops loss of light density on the sensor.)
Light density, yes, but not total light, so it's not so bad. For this reason, you can improve signal to noise and dynamic range with a TC compared to cropping since you can collect more photons from the same scene without saturating. (you could of course also take multiple exposures with the same result with the crop)
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.

heptagon

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Re: TC or Crop? Is there a consensus? Please help!
« Reply #14 on: August 13, 2012, 01:10:11 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.