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DX on FX, a success, with a TC!

Started Sep 23, 2020 | Discussions thread
petrochemist Veteran Member • Posts: 3,619
Re: DX on FX, a success, with a TC!

Tord S Eriksson wrote:

petrochemist wrote:

epozar wrote:

No wonder here - the TC uses only the central part of an image circle

If a 1.5x TC is taking the image from a APSC lens & spreading it to fit a FF sensor it's effectively using all the lenses image circle.

Never heard of a 1.5x TC, all I've used are 1.4X.
I was surprised it worked so well, considering there is an extra number of glass elements in the light path. Much better than using the same Kenko TC on a DX body, for instance!
I expected some vignetting, but I could not notice any.

1,5x TCs are indded unusual, but the number just fiited the sensor sizes better.

I think I have seen a 1.5x in the past but 1.4x, 2x & even 3x are more common. I also have a 1.7x for that matter.

It's not unusual for the image circle of a lens to be somewhat bigger than the bare minimum for covering it's chosen sensor so a 1.4x will usually be enough to take a 1.5 crop lens up to a FF. There's likely to be a smaller proportion of Canon APSC lenses that can use this trick as their APSC is smaaler with a 1.6 crop.

In the past I've tried using a 0.7x focal reducer for using APSC lenses on MFT. the crop ratio is close to 0.7 but it didn't work for the fisheye lens I was trying. The different aspect ratio might have played a part. (The focal reducer only claims to work for FF lenses)

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