Kenko 1.4x vs cropping

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I was wondering if a kenko 1.4x (giving me 420mm over 300mm) would be better without cropping much only to frame it, than cropping in 50% sometimes at iso 800 at 300mm, which is normally ok but some times loses a bit of IQ.
 
Yes, off course it's better to use a TC. Cropping isn't giving you "reach". You'd have to have a very bad lens, and an even worse TC for cropping to give better results than 1.4x TC use.
 
If you are able to shoot at 100 or 200 ISO without the TC, possibly 400 ISO at a push, then you might gain an advantage from adding a TC. If you are already at 800 ISO or more then I doubt very much there is any point in fitting a TC. Since you lose a stop of light you will need to push the ISO higher and you will end up with increasingly noisy pixels which will require downsizing and/or NR in order to yield acceptable IQ. All the TC will do is to make the image larger and noisier which in turn will require you to downsize the picture further, thus negating any expected advantage. If you are handholding then you may need to raise the shutter speed too, to compensate for the increased focal length, and that will put further pressure on your ISO. On top of that, you may find your AF performance is reduced too.

Of course, acceptable ISO depends on the camera body. The figures I've used above assume a 50D.
 
It's only iso 800 at the worst point, normally 400 does me.

It was mainly for cricket as some boundaries I am finding further away than others. Hence the cropping.

I use a nr program which is pretty good for any noise I have found.

Hmmm I might be worth a shot... Won't know till you try I suppose.
 
What do you do with the finished shot ? is it printed/web/wallpaper ?

Do two test shots, one with TC, one without. Crop non-TC to give same image as TC shot

Do your standard processing on both

Then view the results using your standard final output.

WHICHEVER LOOKS THE BEST IS THE BEST :D
 
Pro's of using TC: uses sweet spot in lens (centre circle) and retains the full resolution of the sensor.

Con's of using TC: slower lens may prevent auto focusing and will force increase in ISO to compenate for increased shutter speed to prevent camera shake (probably 2 stops change - 1 for slower lens and one for camera shake).

So - if you can stand the increased noise from the higher ISO, then use a TC - otherwise you probably didn't have a shot anyway. Cropping an image that did not use a TC will still result in the same camera shake issue - albeit with the faster aperture.
 
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