EOS 90D & Rebel T7 won't go below F9 with 100-400mm & 2x extender III

[Drwho1300]

Using a 100-400mm in combination with 2x extender III on Rebel T7 or 90D. Once the extender is installed I cannot drop below F9 but AF won't work past F8. Any suggestions?

[Waddizzle]

You will lose all ability to autofocus.   The 90D will autofocus with a 1.4x, but not the T7. 

[kvbarkley]

Manual focus.

[johnrmoyer]

Auto focus in live view only.

[shadowsports]

Follow the advice of my colleagues.  

For Reference:

[ebiggs1]

Whether it works and/or AF is available or not, it is a bad idea any way. The 100-400mm zoom doesn't have the IQ to give up to be able to use a 2x tel-con. IMHO, of course others have different standards. Personally I wouldn't even use the 1.4 tel-con with it.

[jrhoffman75]

You will get as good or better results by using the bare lens and cropping in post. And you won't take the AF speed penalty or the loss of light penalty.

One of the AI tools like DxO Pure Raw or Topaz Photo AI can improve the image in post.

[johnrmoyer]

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@jrhoffman75 wrote:

You will get as good or better results by using the bare lens and cropping in post. And you won't take the AF speed penalty or the loss of light penalty.

One of the AI tools like DxO Pure Raw or Topaz Photo AI can improve the image in post.

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I disagree. I do not see AI hallucinations as an improvement. https://en.wikipedia.org/wiki/Hallucination_(artificial_intelligence)

For enlarging up to 200%, I think that bicubic interpolation is better. https://en.wikipedia.org/wiki/Bicubic_interpolation , especially Lancoz https://en.wikipedia.org/wiki/Lanczos_resampling 

https://www.rsok.com/~jrm/2024Feb09_SaltPlainsNWR/2024feb09_kestrel_IMG_8938c.html 

American Kestrel (Falco sparverius) at Salt Plains National Wildlife Refuge in Alfalfa County, Oklahoma, United States on February 9, 2024, https://www.rsok.com/~jrm/2024Feb09_SaltPlainsNWR/2024feb09_kestrel_IMG_8938c.html , EF100-400mm f/4.5-5.6L IS II USM +2x III, distance to subject about 45 meters

https://www.rsok.com/~jrm/2024Feb09_SaltPlainsNWR/IMG_8938cs2.JPG 

Same image cropped without downsizing

https://www.rsok.com/~jrm/2024Feb09_SaltPlainsNWR/2024feb09_kestrel_IMG_8938cs4.jpg 

Same image resized to 200% with Lancoz

[ebiggs1]

" And you won't take the AF speed penalty or the loss of light penalty."

Even if post processing is good you still can't eliminate what JohnH opined. Or, perhaps the same results as stated done with cropping in post. We all have our standards which may be different.

[johnrmoyer]

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@ebiggs1 wrote:

" And you won't take the AF speed penalty or the loss of light penalty."

Even if post processing is good you still can't eliminate what JohnH opined. Or, perhaps the same results as stated done with cropping in post. We all have our standards which may be different.

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Post processing.

For low noise images, the small aperture diffraction blur can be removed. The "capture sharpening" in rawtherapee does this. The "digital lens optimizer" in DPP does this. The Richardson/Lucy deconvolution in the GMIC plugin for gimp does this, but it is important not to have any sharpening in other software before doing this in gimp.

The Kestrel image was made using the "Standard" picture style which was the starting point for DPP. All of the changes made from the standard style in DPP are listed below. To me this seems like minimal post processing. Auto lighting optimizer and peripheral illumination correction and distortion correction were turned off in the camera menus. I changed white balance from auto to daylight in DPP.

To me, this image seems to be an accurate representation of the Kestrel. I am sorry that it does not meet your standards. I could not get closer to the bird. The slower AF with extender is necessary to compensate for the 2 times larger focus step, otherwise there would not be accurate focus.

[CanonVRD:Image] White Balance Adj              : Daylight
[CanonVRD:Image] Color Saturation Adj : 1
[CanonVRD:Image] DLO Setting                    : 65
[CanonVRD:Image] Gamma Unsharp Mask Strength    : 3
[CanonVRD:Image] Gamma Unsharp Mask Fineness    : 1.7
[CanonVRD:Image] Gamma Unsharp Mask Threshold   : 3
[CanonVRD:Image] DPRAW Microadjust Back Front   : 1
[CanonVRD:Image] DPRAW Microadjust Strength     : 8
[CanonVRD:Image] Crop X                         : 542
[CanonVRD:Image] Crop Y                         : 657
[CanonVRD:Image] Crop Width                     : 3600
[CanonVRD:Image] Crop Height                    : 2400
[CanonVRD:Image] Crop Rotation                  : 0
[CanonVRD:Image] Crop Original Width            : 5088
[CanonVRD:Image] Crop Original Height           : 3392