topic Re: Focus issues in EF & RF Lenses

RF800mm lens fuzzy on EOS R5 Mark II

CVOHDrider58 — Tue, 24 Jun 2025 13:39:53 GMT

I have the R5 Mark II. Recently i purchased the RF 800 F11 IS STM lens. I have not been able to get the lens to focus. It is like it gets close but the image remains fuzzy. Is there something wrong with the lens or something I am doing wrong?

Re: Focus issues

jrhoffman75 — Tue, 24 Jun 2025 13:26:50 GMT

@CVOHDrider58 wrote:

I have the R5 Mark II. Recently i purchased the RF 800 F11 IS STM lens. I have not been able to get the lens to focus. It is like it gets close but the image remains fuzzy. Is there something wrong with the lens or something I am doing wrong?

Hi. Please provide more info.

1. what mode is your camera in? One Shot AF?

2. Are you trying to focus beyond the minimum focusing distance?

3. Does the subject have sufficient contrast?

4. Do other lenses work OK?

Re: RF800mm lens fuzzy on EOS R5 Mark II

ebiggs1 — Tue, 24 Jun 2025 14:13:47 GMT

"I am doing wrong?"

Without further info my first guess you are too close to the subject. A sample with all your settings would be helpful to solve this dilemma You can also try a full camera reset to factory default settings. You may have set something incorrectly.

Re: RF800mm lens fuzzy on EOS R5 Mark II

johnrmoyer — Tue, 24 Jun 2025 14:15:15 GMT

Are you certain that the "fuzzy" comes from focus? Is any portion if the image in focus? What software are you using to view the image?

The depth of field might be very shallow.

F/11 will result in small aperture diffraction blur with that camera sensor. In the camera when saving a JPG or in Canon DPP software, "digital lens optimizer" will remove some of the small aperture diffraction blur if the ISO is not too high. When the pixels are closer together on the sensor, there will be more small aperture diffraction blur.

If the ISO is high, then noise reduction will blur the image.

In Canon DPP software when editing the CR3 file, one may view the focus points that were selected by the camera.

In Rawtherapee, the "capture sharpening" will remove small aperture diffraction blur.

Re: RF800mm lens fuzzy on EOS R5 Mark II

wq9nsc — Tue, 24 Jun 2025 15:16:56 GMT

800mm is a natural for wildlife photography but with a "best" aperture of f11 it is going to force either high ISO, slower than optimal shutter speed, or a combination of both if illumination is poor. Post some example photos with your exposure (shutter speed, aperture, and ISO info intact) which will be helpful.

I have an EF 800 f5.6 which is 2 full f stops "faster" and with poor lighting it pushes ISO higher than I would like even with my 1DX III which handles high ISO quite well.

Rodger

Re: RF800mm lens fuzzy on EOS R5 Mark II

johnrmoyer — Tue, 24 Jun 2025 17:33:12 GMT

Like wq9nsc, I often use 800mm. But I spent a fraction of the money so I also have F/11 wide open.

https://www.rsok.com/~jrm/2024Oct22_Salt_Plains/2024oct22_eagle_IMG_2015c.html

Bald Eagle (Haliaeetus leucocephalus) at sunrise at Salt Plains National Wildlife Refuge in Alfalfa County, Oklahoma, United States on October 22, 2024

Camera Model Name	Canon EOS R5
Lens Model	EF100-400mm f/4.5-5.6L IS II USM +2x III
Focal Length	800.0 mm
Exposure Time	1/400
ISO	500
F Number	11.0
Camera Temperature	38 C
Measured EV	13.38
Measured EV 2	29

Re: RF800mm lens fuzzy on EOS R5 Mark II

normadel — Tue, 24 Jun 2025 22:57:28 GMT

If you look at the manual for this lens at:

https://www.usa.canon.com/support/p/rf800mm-f11-is-stm

you will see the minimum focus distance is 19.69 feet. Are you closer than that?

Even if you're not, image magnification of close subjects with an 800mm lens will be very large, resulting in very little depth of field.. Magnification and aperture are what determine depth of field.

Re: RF800mm lens fuzzy on EOS R5 Mark II

wq9nsc — Wed, 25 Jun 2025 00:22:47 GMT

BEAUTIFUL composition John!!!

Rodger

Re: RF800mm lens fuzzy on EOS R5 Mark II

kvbarkley — Wed, 25 Jun 2025 00:25:14 GMT

Rodger also hinted at it, but you might be getting motion blur if your shutter speed is not fast enough - like 1/800 of a second!

Re: RF800mm lens fuzzy on EOS R5 Mark II

ebiggs1 — Wed, 25 Jun 2025 14:41:29 GMT

"like 1/800 of a second!"

And 1/1600 is even better. In any case these should be and the point is, they are the slowest SS for a big lens like the 800mm. So without further info the culprit might be too close and too slow SS or both.

Re: RF800mm lens fuzzy on EOS R5 Mark II

johnrmoyer — Wed, 25 Jun 2025 16:55:07 GMT

@ebiggs1 wrote:

"like 1/800 of a second!"

And 1/1600 is even better. In any case these should be and the point is, they are the slowest SS for a big lens like the 800mm. So without further info the culprit might be too close and too slow SS or both.

The Eagle I posted was at 1/400 hand held and panning and 800mm. The softness in that photo is almost entirely from the distortion caused by a long distance with varying air densities. The small aperture diffraction blur has been mitigated by DPP "digital lens optimizer". It was dawn and the eagle was high enough to be lit by sunlight.

The minimum shutter speed with IBIS and lens IS and tracking is different than the old rule of thumb. With more rapid subject movement or a closer moving subject, then a faster shutter speed would be needed.

All edits:

ExifToolVersion	13.30
FileName	IMG_2015.dr4
AngleAdj	3.2
WorkColorSpace	sRGB
WhiteBalanceAdj	Daylight
PictureStyle	Shot Settings
ColorSaturationAdj	1
UnsharpMaskStrength	2
UnsharpMaskFineness	4
UnsharpMaskThreshold	3
ShadowAdj	2
LuminanceNoiseReduction	1
ChrominanceNoiseReduction	1
DLOSetting	60
DPRAWMicroadjustBackFront	2
DPRAWMicroadjustStrength	8
CropActive	Yes
CropRotatedOriginalWidth	8484
CropRotatedOriginalHeight	5913
CropX	1121
CropY	1919
CropWidth	4800
CropHeight	3200
CropRotation	0
CropAngle	3.2

https://www.rsok.com/~jrm/2024Oct22_Salt_Plains/2024oct22_eagle_IMG_2015c.html

Re: Focus issues

CVOHDrider58 — Wed, 25 Jun 2025 18:14:53 GMT

I have tried the A+ mode and in the M mode both, I have been using M mostly with this Camera but tried the A+ to see if it effected this issue. I have tried in Spot AF, 1-point AF, Expand AF, Expand AF area Around, and Flexible AF. Still get the same result. And I have tried at long distances. I am including a couple photos. One taken with my 24 - 105 lens. (All my other lenses work fine.) this to show the distance I was shooting. The other two are the best focus result I obtained.

Re: RF800mm lens fuzzy on EOS R5 Mark II

CVOHDrider58 — Wed, 25 Jun 2025 18:16:13 GMT

I put in more information in my reply to JRHoffman75 above.

Re: RF800mm lens fuzzy on EOS R5 Mark II

CVOHDrider58 — Wed, 25 Jun 2025 18:17:37 GMT

The focus issue happens prior to the shot. All other lenses work fine.

Re: RF800mm lens fuzzy on EOS R5 Mark II

CVOHDrider58 — Wed, 25 Jun 2025 18:18:54 GMT

The attempts are at long distances.

Re: RF800mm lens fuzzy on EOS R5 Mark II

CVOHDrider58 — Wed, 25 Jun 2025 18:20:42 GMT

I do not believe it is shutter blur. I had not pushed the shutter button. I have also used it on my tripod with the same results in blurriness.

Re: RF800mm lens fuzzy on EOS R5 Mark II

wq9nsc — Wed, 25 Jun 2025 19:00:52 GMT

It appears to me that the item best in focus is the bark of the tree between the two red vehicles. With a long telephoto lens, you will generally need to place a focus point on the area of interest in a crowded scene rather than letting the camera "guess".

The depth of field in focus is limited with a telephoto lens even at f11. I am guessing your camera was around 200 feet from the tree that is in decent focus. With an 800mm f11 lens at 150 feet, the total depth of field in focus is around 12 feet so much of what is in the photo will be out of focus. If you are further away, then DoF increases but it is still pretty shallow compared to more normal focal length such as a 200mm lens.

The EXIF data from the image shows it was captured at ISO 10,000 and significant noise reduction takes place at that ISO which will further reduce detail. Some of the AI noise reduction tools do a pretty good job of estimating what is noise and will fill in what the algorithm thinks is the correct missing data but they aren't perfect. With traditional processing, detail is reduced to smooth noise and that is going on to some extent with your image. When noise reduction is applied, severe cropping makes the results far more apparent. If you can frame the capture where the desired image pretty much fills the sensor then you can get away with a far higher ISO than if you need to crop and magnify from the sensor.

Attached photo was captured with an EF 800 f5.6 at around 100 feet and you can see that the grass just inches beyond the target bird is beyond the depth of critical focus. The f11 wide open won't be this shallow but you still won't have a lot of depth of field. Captured with EOS 1DX III and EF 800 f5.6 @ f5.6, 1/800, ISO 1250.

Rodger

Re: RF800mm lens fuzzy on EOS R5 Mark II

johnrmoyer — Wed, 25 Jun 2025 18:48:10 GMT

@CVOHDrider58 wrote:

I do not believe it is shutter blur. I had not pushed the shutter button. I have also used it on my tripod with the same results in blurriness.

The blur appears to me to all be in one direction. I would guess camera motion. Is IS enabled by the switch on the lens?

At 800mm, even on a tripod, the tripod might move enough to create that blur.

Re: RF800mm lens fuzzy on EOS R5 Mark II

CVOHDrider58 — Wed, 25 Jun 2025 18:49:16 GMT

Yes IS is on.

Re: RF800mm lens fuzzy on EOS R5 Mark II

johnrmoyer — Wed, 25 Jun 2025 18:52:39 GMT

@CVOHDrider58 wrote:

Yes IS is on.

What shutter speed?