# Am I losing IQ



## chauncey (May 20, 2016)

By attaching a 2X TC onto a 300mm f/2.8 lens?


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## neuroanatomist (May 20, 2016)

Yes. Compared to not cropping the image. 

No. Compared to cropping to the image without the TC to 25% (to achieve the FoV of 600mm). 

Maybe. Compared to cropping to some intermediate at point.


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## Mikehit (May 20, 2016)

I agree with Neuro.

I don't own a MkIII, but from things I have read some people who would previously not use a 2x the MkIII version is the one that may change their minds.


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## Kristofgss (May 20, 2016)

You can compare that combination to other lenses on the digital picture

http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=739&Camera=453&Sample=0&FLI=2&API=2&LensComp=748&CameraComp=0&FLIComp=0&APIComp=0


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## axtstern (May 20, 2016)

Just out of curiosity:

Would an 400 L 2.8 with a 1.4 III do better?

The original poster did not mention which generation his 300 2.8 is.
My 400mm is first generation so I do not dare to compare it but in general it would be nice to know.


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## neuroanatomist (May 20, 2016)

Kristofgss said:


> You can compare that combination to other lenses on the digital picture



You can, and that's my 'case 1' above, where the images weren't cropped but rather the distance is doubled when the 2x is used**. The TDP comparison is useful – it addresses issues such as comparing 300mm+2x vs 400mm+1.4x vs. native 600mm, comparing MkII vs. MkIII TCs, etc. 

But the tool also gives the impression that adding a TC _always_ reduces IQ, and that's not the case. In fact, I would argue an appropriately-used TC often doesn't reduce IQ – in real world use, if I could just walk closer and cut the distance to my subject in half, I wouldn't use the 2x TC...I'd just walk closer. The TC is used when I _can't_ walk closer, and would need to crop deeply instead, and in that case the IQ is better with the TC. 


**Technically, Byran shoots the native 300mm and the 300+2x at the same distance, but for the latter he uses a test chart that's 1/4 the size (his testing space doesn't allow enough space to frame the large chart at 600mm FL). Because of the chart design (he uses Applied Imaging QA-77 charts, based on the ISO12233 standard), the resolution scales exactly across all four chart sizes when you fill the frame with the chart.


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## Don Haines (May 20, 2016)

The use of a teleconverter ALWAYS degrades the image. 

That said, there are a couple of other questions you have to ask....

Is the degradation of the image enough so that there is a noticeable difference? This depends a lot on the camera and the lens. A camera with a finer pixel pitch will be more likely to show a noticeable difference, hence the rule of thumb that crop cameras, with their smaller pixels, don't work as well with teleconverters as do FF cameras..... A high quality, very sharp lens (can you say big white.....) after the degradation of the image by the teleconverter is still a fairly sharp lens, while kit lenses and many zoom lenses (there are some high quality exceptions) are already showing visible drop in IQ before the teleconverter is added and afterwards it is noticeably worse.... this gives us a second rule of thumb, which is that teleconverters work best on "L" lenses.

When using a 2X teleconverter on a distant object, you will get 4 times as many pixels on the target, but they are lower quality pixels. The question becomes, do these greater number of lower quality pixels resolve more detail than the fewer number of higher quality pixels from without the teleconverter. The odds are that if you are shooting a FF body and "L" lenses, that they do, and if you are shooting a crop camera with a non-L lens, that they do not... anything else and you have to experiment.....

For example, I have a 5D2 and a 70-200 lens. Put a 1.4X teleconverter on it and it resolves more distant detail. Put a 2X teleconverter on it and it resolves even more. Now I pick up a 7D2, and try again.... With the 1.4X teleconverter on, it resolves more detail.... but with the 2X teleconverter the resolving power drops!


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## chauncey (May 20, 2016)

Should have mentioned my goal...create a large print of a hummingbird in flight, more than a 16 x 20.
Figured that 600 mm would be better than 300 mm at close to minimum focusing distance.
Am adept at photo-merging in PS CC.
1Ds Mk3


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## AlanF (May 20, 2016)

Don Haines said:


> The use of a teleconverter ALWAYS degrades the image.
> 
> That said, there are a couple of other questions you have to ask....
> 
> ...



+1
300mm f/2.8 + 2xTCIII on my 5DIII = great and better than 1.4xTC III.
On my 7DII or 5DS R, not so good and I prefer the 1.4xTC at 420mm.


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## neuroanatomist (May 20, 2016)

Don Haines said:


> The use of a teleconverter ALWAYS degrades the image.
> 
> When using a 2X teleconverter on a distant object, you will get 4 times as many pixels on the target, but they are lower quality pixels. The question becomes, do these greater number of lower quality pixels resolve more detail than the fewer number of higher quality pixels from without the teleconverter. The odds are that if you are shooting a FF body and "L" lenses, that they do...
> 
> For example, I have a 5D2 and a 70-200 lens. Put a 1.4X teleconverter on it and it resolves more distant detail. Put a 2X teleconverter on it and it resolves even more.



So NOT _always_, at least when considering the final output (which is what really matters).


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## Don Haines (May 20, 2016)

neuroanatomist said:


> Don Haines said:
> 
> 
> > The use of a teleconverter ALWAYS degrades the image.
> ...


Correct! You can have cases where in theory the image is degraded, but the camera is not able to notice those changes.

Teleconverters are one of those things where there is no set answer as it depends on so many variables....


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## awinphoto (May 20, 2016)

Hanging around too much on these forums may help you lose more IQ than teleconverters... Let me heat up the popcorn.


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## neuroanatomist (May 20, 2016)

awinphoto said:


> Hanging around too much on these forums may help you lose more IQ than teleconverters... Let me heat up the popcorn.



*TCs make you lose DR.* 

There, that should get things rolling. ;D


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## awinphoto (May 20, 2016)

neuroanatomist said:


> awinphoto said:
> 
> 
> > Hanging around too much on these forums may help you lose more IQ than teleconverters... Let me heat up the popcorn.
> ...



Hahaha... Darn that blasted DR haha


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## chauncey (May 20, 2016)

Dynamic range is one of the things that can be remedied, among other problems, in PS CC, but...
IMHO, poor IQ pixels cannot be fixed.

So, is it better to upsize fewer MP than to zoom-in with the TC?


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## unfocused (May 20, 2016)

awinphoto said:


> Hanging around too much on these forums may help you lose more IQ than teleconverters... Let me heat up the popcorn.



My thoughts exactly. Every time I comment on this forum I feel my IQ slipping away. Probably negative by now.


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