RF 100-500mm F4.5-7.1 L IS USM, Auto Focus focuses too close

[carl_schnurr]

I just returned from a great week in the rainforests of the OSA peninsula in Costa Rica.
I took a lot of photos of birds and monkeys high up in the trees.
I had difficulty as the the AF seemed focus very close.  I had to manually focus farther out before I could get the AF to zero in on my subject.  Alternatively I could find something close to focus on and gradually raise the camera so the subject gets progressively farther away, until I was pointing at the subject.
This issue eliminated any Bird in Flight photos for the entire trip.

Here is my set up.

• R6 Mark ii
• Manual Mode, Auto ISO, with max set to 6400, typically wide open aperture.
• AF set to Animal Eye detect, Case1.
• RF 100-500L lens, with buttons set to 3m to infinity, AF ON, Stabilizer ON, Stabilizer Mode 1.

I tried varying the following camera settings but didn't notice any difference

• ONE SHOT and SERVO AF
• Different AF area shapes
• Whole Area tracking Servo AF ON/OFF
• Back Button Focus ON/OFF

Here a couple things that were different.

• Before leaving I thoroughly cleaned the front and back lens elements, both sides of my UV filter and the electrical contacts on the lens and camera
• The heat and humidity were fairly high, the first time shooting there was a build up of condensation on the back lens surface which evaporated immediately when I removed the lens for a minute.
• This is my first time using a USB charger for the camera batteries, and they appeared to fully charge as desired.

I also took a RF24-70 f2.8 lens which did not show any of these problems.

Since returning I have been trying to trouble shoot this issue.
I set lens to 500mm, f7.1, with camera touchscreen closed to avoid any errant touch screen focusing.
I tried several ISO/Av combinations with the same results.

With camera set to ONE SHOT, I am able to turn the focus guides ON; and they become visible when I manually adjust the focus ring.  When I have the lens focused on an object far away and then aim the AF point an object 7m away from the camera, it cannot achieve auto focus, and the focus guides are grey until I manually focus to get close to the subject being in focus.  Similarly when focused on object 7m away, and then aim the AF point at an object 4m away, it cannot achieve autofocus; and the focus guides are grey until I manually focus to get close to the subject being in focus.

Camera set to SERVO AF, focus guides are not visible, (should they be?)
Essentially the same result, except instead of focus guides being grey, the focus point is coloured Red, until I manually focus to get close to the subject being in focus and it turns Blue.

The lens needs to be fairly accurately dialed into the correct focus distance for the AF to kick in.  Do you recommend getting it repaired, or is there something else I can try?

[March411]

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@Waddizzle wrote:

Photographing wildlife surrounded by leaves and branches is most often quite challenging, as you seem to have discovered. The camera has natural tendency to want to lock focus on the nearest subject to the camera. 

Every difficult scenario is a little different.  There will always be a scenario where you cannot get the shot you want.

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Carl, I would agree with waddizzle. This is one of the reasons why I have the dual back button focus set up the way I do, allows me options when something isn't going as planned. 

Wildlife in dense woods and low light, I will more often than not use my * button set up for metering and AF start, spot focus and use the joystick/multi-controller to hit the eye. Twigs, leaves and birds/bugs fly through the scene will fool the AF. Your hit rate will improve greatly in this environment if you take control. 

[SignifDigits]

Carl,  Thanks for joining us and sorry for your woes on your trip.  I had a lens release fail on vacation - was a real bummer as I really didn't want to shoot everything at 16mm.

Quick question to clarify - are you only using Canon branded batteries?  You say "

• This is my first time using a USB charger for the camera batteries, and they appeared to fully charge as desired."

Thus, I wanted to double-check you're not using third-party batteries that have the USB ports directly into them.  I had trouble with these batteries not driving my focusing motors correctly on my RF 200-800 - they failed in a similar way that you describe.  Even though their specifications for milliamp hours are higher and voltage is the same I had issues that disappeared when I put the Canon battery back in.  

They work fine in less stressful situations, but I'm kicking them to the curb as they aren't 100% reliable.  And, as my colleague Wadizzle points out elsewhere they are one firmware upgrade away from being useless.

I realize this probably isn't the case for your situation, but wanted to double check.

[carl_schnurr]

I'm used to missing shots, this experience was noticeably different. Much more that would be attributed to UV filter or just poor lighting.  Every time I pressed the AF, the lens focused very close, likely 3m and
I manually adjusted the focus close to the subject. Even photos in open sky!

I've got to thank this forum, you really nailed what I now believe is the root cause.

deeebatman316 recommended that I adjust camera settings menu AF3, "AF preview" to OFF, and "Lens drive when AF impossible" to ON.  I noticed a substantial improvement with this ON.

Waddizle suggested not cleaning with fluids.
The day before I left, I cleaned the lens. With back element pointing straight up I placed two drops of OPTEX Lens cleaner (alcohol free) solution directly on the back glass. Totally forgot about that being a no-no.
The first time using camera in Costa Rica, I had condensate form on the back element of the lens.

Its feasible that a small amount of cleaning solution was left captured internally in the lens after cleaning.
The warm climate heated it up and it evaporated internally with some condensing on the lens.
In Costa Rica, I took the lens off, and watched the condensate evaporate from the back element. I didn't wipe the back element for fear of contamination.  When I returned home, I inspected the back element with a magnifier but couldn't see any contamination or streaks. But condensate would be spread out evenly, and any optical degradation across the entire surface may not be visible, but affect AF.

Yesterday, I cleaned the back surface with a drop of cleaner on a microfiber cloth, and noticed a slight but noticeable improvement in AF.

Could my experience be the result of both these things.  If the rear element was contaminated, the AF might be slow or might not be able to find focus. With the "Lens drive when AF impossible" set OFF, it would stop trying.
Does this sound reasonable?

I do not think my batteries or method of charging was a factor.  I have 2 Canon LP-E6NH batteries typically charged with the Canon 110V wall charger. In Costa Rica I used an off brand USB-C charger powered by a battery pack or wall adapter.  I tested and found no noticeable difference between the batteries charged with my Canon 110V wall charger;  my USB-C charger connected to a USB-A wall adapter; or my USB-C charger connected to a battery pack.  All methods of charging both batteries were able to charge up to 100% per camera Battery Info (menu Yellow5), and recharge performance green (3 bars).  All methods had similar deterioration of AF.
At 26% I noticed AF start to slightly deteriorate, and at 15% it became an issue..

[carl_schnurr]

As requested, here are some of my photos.  All were taken by manually adjusting the focus.

[March411]

Fantastic grabs Carl, I really am a big fan of the last frame. Nicely done working with the lens handicapped!

[ebiggs1]

" I tried removing the UV filter but it had no impact"

You need to stop using this filter as pointed out it is not necessary and although you didn't see an immediate impact it still has a detrimental effect on the lens. If you are concerned about front element damage, me too, a protecto filer of high quality is better. Example might be the B+W MRC MASTER 007 Clear Filter. And always remember filters screw off as easily as they screw on if need to.

I can't give you exact suggestion of the best AF settings since I haven't used the 100-500mm lens but I can say it should  never not be able to AF. The advanced setting features on the new camera models only enhance them. Therefor, and perhaps, not what you are wanting to here, if there aren't any issues with the lens itself, the issue is your technique. Almost all OOF or unable to achieve focus is caused by user error.

[SignifDigits]

@ebiggs1 Was your statement "...it still has a detrimental effect on the lens.." intended to state "... it still could (I believe the better US filters generally do not) have a detrimental effect on the image..."?  I've never heard of a UV filter damaging a lens, and the research I've seen is that sharpness is generally not affected even by inexpensive lenses but that the inferior coatings can certainly cause other undesirable effects.  I've seen that UV treatment is not useful versus your recommended clear lens, but somehow I find the habit hard to break, and have only had issues with personally with ghosting and flare.  That said, if I really want the best images and have the time I make sure to take the filter off.

[ebiggs1]

SignifDigits

" I've never heard of a UV filter damaging a lens, and the research I've seen ..."

I didn't say it damages the lens. A UV filter, any filter, can effect AF . It certainly can and is very well proven that  some lenses do not do well with a UV filter. Is the 100-500mm one of them, I don't know first hand since I have never used one but the possibility is there. If a person is seeing issues the filter should be the first thing to go.

Here's the problem, and I am not meaning to be disrespectful to anyone but still the facts are, I make every effort to talk from experience not for someone else's "research" or review. I have had the opportunity to work (40 years) for a large company that has access to every piece of photographic gear made. I had my own photography business and my hobby after retirement was to 'play' with lenses. I bought and messed with and sold so many I can't give an accurate number. I probably still have 40 in my formerly stop bath stained darkroom converted to storage room. So, if I haven't done it personally I admit it or I don't respond. I don't read or watch reviews or rely on others "research" for my opinions. Most of that stuff isn't worth the pixels it take to display it. On the other hand guys that do that and live that can be helpful because they know every spec and feature of every Canon gadget, gear or lens. Like a book!

However, if you think using a UV filter is the way to go you need to do it. A man should do what he thinks is best.

BTW, I agree with Marc, "Fantastic grabs Carl,..."

[March411]

There has been a lot of conversation around the topic of using UV filters or filters in general on lenses. First and foremost, they are redundant as sensors these days already manage UV light. To ebiggs point, many have reported using filters to be detrimental on both the RF 100-500mm and RF200-800mm.

As to using them to protect a lens, if you are in an environment where water, mud, dust and dirt are at risk for flying onto your front element using a filter is a good play. If you are looking for a particular creative effect or want to adjust color tones filters are great for the artistic value.

My specific experience with both my RF 100-500mm and 200-800mm is that UV filters when I have used them for protection do impact, degrade image quality as it relates to sharpness and contrast. There have been occasions where the environment dictated using a filter and I own some high-quality filters and still had some flaring, annoying artifacts and focus racking.

Generally, none of my lenses have filters unless the environment dictates, I protect the front element from flying “stuff” and the balance of the time the lens hood is my source of protection. Many of my friends and associates use them as I described but never have them mounted permanently for protection.  

[SignifDigits]

Many thanks to both Marc and ebiggs1.  I have definitely seen ghosting and flare issues myself.   I've also had some filters that I've had to toss due to damage to the filter (and was glad it wasn't the front of the lens).  But that was not whilst shooting - at least I didn't think so, but I'm not not 100% sure of course as I typically put the lens cap back on.  I just ordered a couple B+W MRC Nano UV filters.   Guess I'll send those back and get B+W or Canon clear protectors instead.  Again, many thanks for clarifying that "detrimental effect on the lens" means "detrimental effect on the lens image" or "detrimental effect with the lens".  I just couldn't figure how how a UV filter could damage a lens, but you guys are so much more experienced I just wanted to be sure.

As I said, it was a habit from the film days, and I DO still want something up there if I can do so without damaging image quality - just...in...case.