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Archive 2016 · TC or crop?

  
 
arbitrage
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p.1 #1 · p.1 #1 · TC or crop?


TC or crop without TC? I've always been a fan of TCs vs just cropping more....somedays I really don't know though.

What are your thoughts?

Here are two images shot just seconds apart. One is 400mm and the other 560mm. Then cropped to the same FOV to present on here. Both are significant crops. The originals are below. Can you tell which is which from the crops?

I should also note that in this example I didn't take advantage of my extra stop and shoot wide open without the TC. That would have resulted in less noise. By stopping down the non-TC shot I may have gained some sharpness?? The TC shot is wide open.

Also found that the TC shot actually robbed the shot of 1 1/3 stops of light and I normalized this in post. This is 200-400 with built in TC.






















Jul 20, 2016 at 05:57 PM
RustyBug
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p.1 #2 · p.1 #2 · TC or crop?


My .02 is that a TC will have a reduction in contrast as the light is "spread" further. The diff is subtle, and of course the offset in processing (USM) vs. enlargement can make it even more challenging to differentiate.

That said, I'm guessing (laptop monitor) the 2nd one is the TC shot.



Jul 20, 2016 at 06:15 PM
chez
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p.1 #3 · p.1 #3 · TC or crop?


Depends on what the final goal of your image is. If to display on the net...then cropping is fine, but if its to print of any significant size then the more resolution the better. If the images from the two techniques basically look the same to you, I would go with the one which results in more resolution.


Jul 20, 2016 at 06:33 PM
jcolwell
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p.1 #4 · p.1 #4 · TC or crop?


I find that using a quality TC provides better IQ than cropping to the same framing, using the same camera. OTOH, I also find that using a single 2x TC and cropping it a further 1.4x gives better IQ than stacking a 2x and 1.4x TC.


Jul 20, 2016 at 06:34 PM
EB-1
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p.1 #5 · p.1 #5 · TC or crop?


Normally I use a TC if the main lens is a prime, then I'd consider cropping if there is not enough reach. It's not like the old days where the croppers always had higher resolution than FF.

EBH



Jul 20, 2016 at 06:35 PM
Pixel Perfect
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p.1 #6 · p.1 #6 · TC or crop?


Yay just buy a 5DsR and crop the buggery out of that sucker and still end up with a ton of pixels to play with.

I'm of the school that thinks TC at least 1.4x trumps cropping, but it does come down to how many pixels you have to start with. 5DsR outputs same number of pixels on subject as 1DX + 1.67x, so for pixel challenged FF like 1DX I'll definitely reach for the TC, but 5DsR depending on the lens and speed of the subject I'd rather use bare lens in many cases knowing I've still got more pixels than 1DX + 1.4x.



Jul 20, 2016 at 07:52 PM
rscheffler
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p.1 #7 · p.1 #7 · TC or crop?


Don't have an answer to your original question, but will confirm that the 200-400 with 1.4x engaged seems to lose 1.3 stops, rather than one stop of light. Sometimes I will adjust the shutter or ISO accordingly, but usually will just equalize it later in post. I've also noticed use of the TC introduces a very slight greenish tint to overall color.


Jul 20, 2016 at 09:39 PM
rabbitmountain
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p.1 #8 · p.1 #8 · TC or crop?


Pixel Perfect wrote:
Yay just buy a 5DsR and crop the buggery out of that sucker and still end up with a ton of pixels to play with.

I'm of the school that thinks TC at least 1.4x trumps cropping, but it does come down to how many pixels you have to start with. 5DsR outputs same number of pixels on subject as 1DX + 1.67x, so for pixel challenged FF like 1DX I'll definitely reach for the TC, but 5DsR depending on the lens and speed of the subject I'd rather use bare lens in many cases knowing I've still got more
...Show more

+1 but only true at low ISO.



Jul 22, 2016 at 10:39 PM
rabbitmountain
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p.1 #9 · p.1 #9 · TC or crop?


TC is always preferred if sharpness becomes relevant in PP. Mounting a TC takes time and can keep you from getting the shot. I have lots of sub 400mm shots using a 100-400ii w/ 1.4xiii. No time to take the TF off. That is the flip side of the TC coin.

I can't tell which is which on my phone. But I think at this output size it's a draw anyway.



Jul 22, 2016 at 10:42 PM
tshore
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p.1 #10 · p.1 #10 · TC or crop?


The tradeoff is between resolution and sharpness. The cropped image will be sharper, because the additional elements of the tc will degrade the image from the base lens if only slightly. But the cropped image loses resolution compared to the image using the tc, because the cropped image has fewer pixels with which to capture the sharper image. Optimal solution is to crop, combined with a higher pixel-density sensor.



Jul 22, 2016 at 11:21 PM
melcat
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p.1 #11 · p.1 #11 · TC or crop?


tshore wrote:
The cropped image will be sharper, because the additional elements of the tc will degrade the image from the base lens if only slightly.


Much more than that: the teleconverter is taking the central 0.7 of the lens's image circle and blowing that up to fill the sensor. Even if it were optically perfect, the centre of the image is only 0.7 as sharp. (Depending on the lens, the edges might improve because you're throwing the edges of the original lens's image circle away, and edges are often weaker - though IME not usually on a tele.)



Jul 23, 2016 at 12:06 AM
D.Hussey
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p.1 #12 · p.1 #12 · TC or crop?


I would say that if you're getting images of this quality with a TC then I think it is the way to go, especially with the 200-400 where switching TC in or out is so convenient. That said, I believe there will be circumstances where cropping will yield better results such as in low light where when the light loss from the TC is going to compromise ability to focus or keep ISO within acceptable range


Jul 23, 2016 at 12:45 AM
melcat
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p.1 #13 · p.1 #13 · TC or crop?


With respect to noise, if the teleconverter lost you exactly 1 stop of light (instead of 1.3), the increase in noise would be the same using either the teleconverter or the crop:

- for the teleconverter, half the light is lost because of the 1 stop decrease in aperture

- for the crop, half the surface area of the sensor is unused, hence only half the light gathered.



Jul 23, 2016 at 01:29 AM
jcolwell
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p.1 #14 · p.1 #14 · TC or crop?


melcat wrote:
...crop, half the surface area of the sensor is unused, hence only half the light gathered.


The sensor area for a Canon 1.6x CF camera varies between 0.38x and 0.39x of a full frame sensor camera. Just sayin.



Jul 23, 2016 at 06:59 AM
melcat
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p.1 #15 · p.1 #15 · TC or crop?


The question was about cropping down in post from a full frame image to the same field of view that you'd get from adding a 1.4x teleconverter.

1/(1.4 **2) ~= 0.5 (really, exactly half since the 1.4 was sqrt(2) to start with).



Jul 23, 2016 at 08:00 AM
Liquidstone
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p.1 #16 · p.1 #16 · TC or crop?


Is it strictly an "or" question?

I'd go TC + TC, and crop!



Jul 23, 2016 at 08:16 AM
Sy Sez
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p.1 #17 · p.1 #17 · TC or crop?


I don't "see it" as a conclusive "yes or no" "scenario".

There are many variables that could" tilt the scale" either way; such as the lens used, the sensor resolution, distance to subject, atmospheric conditions, etc.-etc.

The only way to get infinitive answers, would be to take" with / without" shots in a variety of conditions, & do a careful analysis of the results.



Jul 23, 2016 at 09:32 AM
Abbott Schindl
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p.1 #18 · p.1 #18 · TC or crop?


I'm with Sy: there's no simple "use it or don't" guidance I can think of for cropping vs TC. In the OP's example, the 1.3x exposure increase could be due to 2 factors:
- T/ number of the lens+TC (the TC adds elements that reduce the light arriving at the sensor more than just the 1-stop you'd expect from adding the TC).
- Cropping changes what the light meter sees; I often see disproportionate exposure changes when I use a TC.

In addition, for us who have to add a dedicated TC as opposed to flipping a built-in TC in/out, there are considerations like:
- Can an acceptable image be gotten with the exposure changes needed to accommodate the TC?
- Which TC is being used (Canon? I, II, or III? Tamron? Another brand? 1.4x, 2x?)
- Which lens is it being used on?
- Which camera? (How does the camera's AF do at lower light levels?)
- Is the camera supported adequately for the lens + TC?

For cropping:
- Will the resulting crop have enough pixels covering the subject to enable you to use the image as intended? (Severely cropped 1Dx images have a LOT fewer pixels than 5DS images cropped the same amount, for example).
- If you needed to increase ISO to accommodate the smaller f/stop, would the resulting noise be acceptable?

And for both, as Sy Sez, are you using cropping/TC to compensate for an inability to get closer to the subject? In which case the TC will magnify atmospheric effects at full-sensor magnification, whereas cropping probably won't show more atmospheric stuff because of the effectively lower resolution of the crop.

I often use my 500 f/4L II, and sometimes the 100-400 (II), with a TC1.4 (II) or III) and rarely with a TC2 (III). My older 100-400L (I) fared much worse with a TC1.4 (II) and wasn't very useful with a TC2. The 180L macro does pretty well with a TC1.4. I've read wildly inconsistent experiences with various third party extenders used on third party lenses. In the end, I've tested each of my lenses that can take a Canon TC with/without the TC and made my own call about whether/when I can use a TC and when not.

Bottom line is that if you want to use a TC, consider trying it under noncritical conditions before taking it into the field. Also, be sure to check MFA: lens + TC usually requires (for me) different MFA correction than bare lens. Also, Liquidstone's point is well taken: it depends on the image—sometimes you need both TC AND cropping to get the composition you're after.



Jul 23, 2016 at 11:16 AM
RustyBug
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p.1 #19 · p.1 #19 · TC or crop?


Sy Sez wrote:
I don't "see it" as a conclusive "yes or no" "scenario".

There are many variables that could" tilt the scale" either way; such as the lens used, the sensor resolution, distance to subject, atmospheric conditions, etc.-etc.

The only way to get infinitive answers, would be to take" with / without" shots in a variety of conditions, & do a careful analysis of the results.


+1 @ variables

From the standpoint that the TC (by physics design) takes a contrast penalty hit, if the lighting has good contrast characteristics to endure the slight hit to contrast ... then I'd say go TC.

Conversely, if the lighting is of the low contrast variety, I'm inclined to think that the TC contrast penalty on top of the low contrast lighting would rear its head more than the crop without TC would. Kind of a choose your poison scenario.



Jul 23, 2016 at 03:47 PM
AJSJones
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p.1 #20 · p.1 #20 · TC or crop?


Cropping forces you to make do with a fixed amount of information that can be captured by that area of the sensor. Any enlargement in pixel number from it is fictional - high spatial frequencies will be losr and cannot be "interpolated".. A converter spreads that "information" over more pixels so, even if the image is degraded a little, the TC has the potential to capture more information. The capture high frequency limit in the incoming image will be higher. S/N, shutterspeed, aperture/DoF, ISO noise etc will remain additional variables on IQ.


Jul 23, 2016 at 07:50 PM
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