RF 200-800mm - is "heat shimmer" affecting AF?

[Marco Nero]

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I've seen some reasonably good images from this lens so I'm not concerned with it's results. Some reviewers were happy with it and it's clearly going to be popular for the additional zoom on the far end, especially for well lit wildlife photography during daylight hours.
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Duade Paton (see embedded video below via YouTube) has been working with the new and upcoming Canon RF 200-800 mm F6.3-9 IS USM Lens and has a recent video up showing he has experienced a not-so-insignificant number of super-soft images from this lens that he described as "completely unusable" when doing his review for the lens. You can see some of his examples here. This guy is an experienced photographer who specializes in birding and he's familiar with most equipment out there. The video he posted also shows some Live View footage of the AF struggling to remain locked on the subjects repeatedly.
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He mentions that another photographer, who is a friend, appeared to experience the same issue at another time and place. I would agree that heat shimmer could affect some images but not quite with the same consistency we're seeing in the examples he posted as these are very soft and appear to be out of focus. Images on his video show an out of focus subject where nearby insects appear to be in focus... suggesting it's not atmospheric distortion ruining shots.
.



.
I suggested that the failure to focus properly is not necessarily connected with "heat haze" but was more likely related to the unusually long focal length of the 200-800mm lens combined with narrow aperture, resulting in a significant change in contrast to the scene. This is something Canon has previously addressed with their EF and RF Extenders by adding a tiny microprocessor that literally slows the AF down to increase exposure and AF accuracy from the lens. The 2x Extenders are programmed to slow down AF by 75% and the 1.4x Extenders slow the lens down by around 50%. This is by design and its to allow more accuracy with the AF. Canon were well aware of contrast with certain apertures and focal lengths combining to hamper AF.
.
When combined with an APS-C sensor (like that of the R7), it would appear this lens is perhaps punching above its weight and paying the price in certain lighting conditions, depending on the distance to the subject. Of course, it's still good value for money if it can deliver. Thermal Fluctuations and Heat Haze can indeed be a problem when using long lenses on subjects a long way away. I've experienced this myself and yet I find the heat shimmer is very consistent in each frame and you can see this shimmer when playing back images or video. I think it's a good assumption that heat haze might affect AF but that it's more likely that the combined focal length on the R7 is producing contrast at that time and place that produces problems that Canon have observed in the past when coupling extenders with certain lenses. It's also why Canon expressly don't recommend stacking Extenders because they claim that contrast is then impacted to the point where even the optical coatings don't produce enough contrast for the AF to be reliable.
.
To the birders and long-lens users out there, how much of a problem has heat shimmer presented to you? I've dealt with it under certain conditions with distant subjects when using long lenses, especially with APS-C and especially with Extenders. It's normally not a problem and never seems to present itself as an issue with a FF sensor (for me at least). But I'm presently of the opinion that in this instance it may come down to the lens design (aperture range coupled with focal length and high ISO) combined with APS-C sensors at times of the day when contrast is lower. The Eye Detect AF on the R-series cameras is particularly effective and is generally quite reliable on all models. But I feel that the use of this lens on an APS-C (giving around 1200mm) will push the boundaries of reliability if everyone is shooting at 800mm with an APS-C camera.
.
Duade is assuming the problem is Heat Shimmer but he leaves room for speculation or for people to suggest an alternative explanation. I'm not entirely convinced it's related to Thermal issues but I'm sure it could influence the results. I've seen other examples by birding photographers shooting close to the ground over rocks in the hot sunlight where they had no problems at all with this lens (see samples by OrmsTV). Reviewer Hugh Sweeny has also observed unacceptably soft images from this lens yet I thought they were close enough to being sharp in most of his examples. Though the contrast was higher when the shots were crisper. Anyone have any thoughts on the subject?
.





--
Regards,
Marco Nero.

 

[David Franklin]

I have no idea of the focusing performance of the 200-800mm lens, but I do know a bit about heat shimmer. As a former high end car shooter, I often encountered a huge problem with heated air rising off of blacktop surfaces of the roadbeds that are autos’ natural environment. If there is a significant difference between the general ambient air temperature and air heated by contact with a warmer ground surface like for instance, blacktop on a summer day, the differential of temperatures between them refracts light reflected off your subject that reaches your camera through that medium - air.

This phenomena is very difficult to avoid in the many circumstances in which it occurs. Eternal vigilance is the price paid to have sharp photos in warm weather with long lenses. They increase the likelihood of this issue by usually being further away from your subject and thereby increasing the probability of heat shimmer rising up in the greater distance of the path between subject and camera and magnifying the effect by the magnification of focal length compared to shorter lenses.

 

[Franz Kerschbaum]

... and the thermally unstable air causes wavefront errors (i.e. phase fluctuations). No wonder a phase difference AF is confused.

 

[pawn]

As mentioned by others, heat shimmering is not specific to this lens. I often see it at airshows and I used other lenses.

 

[drsnoopy]

And it’s not necessarily “heat shimmer” - it can occur in the cold. It’s due to temperature differences causing turbulence in the layers of air between you and your subject. Photographing walrus and reindeer in Svalbard - in the Arctic - I’ve had terrible shimmer. I was using an R7 and RF 100-500 at 500mm. You can expect if with any long effective focal length with any camera at long distance when shooting over land or water - or in my case, frozen ground, snow and ice.

 

[Marco Nero]

Some very interesting comments and observations from other members here with experience using longer lenses. I appreciate the answers and comments from you.
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I had experienced the effects of thermal fluctuations in the air myself with similar distances when using Extenders on other lenses but none that affected Auto Focus to the point where the subjects were so out of focus. One of the images shown by Duade shows a duck in profile and yet an insect which is out of the AF zone is in (apparent) focus. The duck itself is not. I would assume that any heat shimmer strong enough to defeat the AF and soften the subject would also render nearby subjects similarly soft. I can't help but get the impression that the AF itself is failing (presumably due to contrast issues in the light) resulting in the AF being tricked into locking onto a 'false' subject. He appeared to be getting inconsistent and wildly inaccurate AF responses rather than simply soft images in his Live Video shots... that AF reticule was all over the place!
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You can see one of the insects near the ridge on the back of the duck is in focus.

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I rarely hear about the subject of heat distortion for other photographers and it doesn't seem to come up in conversation here all that often. I'm going to presume that with more people having access to this lens, many of whom will be deliberately adapting it to an EOS R7 (or similar) for additional zoom/reach, that we'll see more complaints about being unable to get sharp shots under certain conditions. It's didn't impact all of the pictures that Duade was shooting, just those at certain times of the day and in certain locations. So thermal issues in the air are always likely in the conditions presented.
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I'm interested to see what the results are from other photographers are when this lens becomes more widely available. The price range this lens occupies should attract a lot of new shooters wanting that extra reach, many of them using APS-C. I have no idea if this will present a problem though I expect that any complaints will surface quickly.

--
Regards,
Marco Nero.

 

[SimonHuang]

It's not the problem of the lens or the camera, it the problem from nature. That how it is!

No matter $1,000 lens $10,000 lens used, in the same distance, you will get the same result!

 

[JayLT4]

Heat haze/atmospheric distortion has always been a thing of course, just might be something popping up more often considering the batches of mega-zoom lenses being released. I see it all the time though being in Arizona and Phoenix specifically, "heat shimmer" and just bad air from the air quality is a common battle.

I just received the RF 200-800 on Thursday of last week and decided to take it out to my local Air Force base to see how it did with some jets. In this case I was using it with my R5, as I normally do when I'm out there.

In the early morning I didn't see too much of an issue as jets were coming in for landing, but as the sun started to pop out more and the air warmed up I saw right away that any distance shots were complete mush. And when NOTHING is in focus there's really not much you can do, there's no camera setting you can change to get around it. I just has to deal with shooting the jets when they were closer.

Here's an un-edited shot of an A-10 coming in for landing. The jet is pretty small in the frame, but not terribly so, and I've taken shots like this before and was able to get nice sharp shots, but the air on that day was very thick and humid (it had rained over night and into early morning)



Here's a shot as the plane got closer and passed by, and I was pulled back to 288mm



I really wanted to see 800mm on this lens though so I decided to follow one of the F35s coming in and just hold the lens at 800mm and track it coming in for landing. This shot is uncropped



This shot showed me that this lens has plenty of potential to be sharp at 800mm. Is this a perfectly sharp shot? No, but I take the hit for that one...following a jet coming in at 800mm isn't something I normally do and just keeping it at a decent spot in the viewfinder wasn't easy, I was a bit unsteady I suppose!

I very much see this issue becoming much more prevalent though, and see the posts of "nothing is sharp!" coming because of it, and unfortunately heat haze/shimmer is not always an easy thing to explain, and accept as an answer.

--
My Flickr page; https://www.flickr.com/photos/jaylt4/

 

[Nimonus]

It happened to me few times also on my 600mm/800mm.

Mostly happened on early morning and only after few minutes stepped out of the car.

I do think it's the temperature, humidity difference between the lens/sensor and environment causes the AF in trouble. There may be a film of condensation formed on the lens elements or sensor.

Remove the lens hood solve my issue very quickly.

 

[robgendreau]

I rarely hear about the subject of heat distortion for other photographers and it doesn't seem to come up in conversation here all that often. I'm going to presume that with more people having access to this lens, many of whom will be deliberately adapting it to an EOS R7 (or similar) for additional zoom/reach, that we'll see more complaints about being unable to get sharp shots under certain conditions. It's didn't impact all of the pictures that Duade was shooting, just those at certain times of the day and in certain locations. So thermal issues in the air are always likely in the conditions presented.

Heat shimmer is so common I doubt anyone would bother to complain about it here. I would assume some noobs might be unaware before they buy such a long lens, but they will encounter it soon enough for any distant subject.

 

[EJ Fudd]

I have shot photos with this effect

Eagles on a partially frozen lake and air temp of about 18 degrees F

so you have water temp, ice temp, air temp and land temp..all factors

 

[Chris Wolfgram]

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I've seen some reasonably good images from this lens so I'm not concerned with it's results. Some reviewers were happy with it and it's clearly going to be popular for the additional zoom on the far end, especially for well lit wildlife photography

It kills me every time I hear this. I swear if I had a penny for every time I've heard "needs good light" about my super slow 800 F11, I could buy three 200-800's lol

I've gotten to where I look out the window and see clouds, and I'm like, "Cool ! I'm going to go shoot some birds" ! But with a clear blue sky I might think.... "Eh..... it's already 8am By the time I get out there, the light is going be harsh, and not worth shooting in Maybe this evening" ?

during daylight hours.
.
Duade Paton (see embedded video below via YouTube) has been working with the new and upcoming Canon RF 200-800 mm F6.3-9 IS USM Lens and has a recent video up showing he has experienced a not-so-insignificant number of super-soft images from this lens that he described as "completely unusable" when doing his review for the lens. You can see some of his examples here. This guy is an experienced photographer who specializes in birding and he's familiar with most equipment out there. The video he posted also shows some Live View footage of the AF struggling to remain locked on the subjects repeatedly.
.
He mentions that another photographer, who is a friend, appeared to experience the same issue at another time and place. I would agree that heat shimmer could affect some images but not quite with the same consistency we're seeing in the examples he posted as these are very soft and appear to be out of focus. Images on his video show an out of focus subject where nearby insects appear to be in focus... suggesting it's not atmospheric distortion ruining shots.
.



.
I suggested that the failure to focus properly is not necessarily connected with "heat haze" but was more likely related to the unusually long focal length of the 200-800mm lens combined with narrow aperture, resulting in a significant change in contrast to the scene. This is something Canon has previously addressed with their EF and RF Extenders by adding a tiny microprocessor that literally slows the AF down to increase exposure and AF accuracy from the lens. The 2x Extenders are programmed to slow down AF by 75% and the 1.4x Extenders slow the lens down by around 50%. This is by design and its to allow more accuracy with the AF. Canon were well aware of contrast with certain apertures and focal lengths combining to hamper AF.
.
When combined with an APS-C sensor (like that of the R7), it would appear this lens is perhaps punching above its weight and paying the price in certain lighting conditions, depending on the distance to the subject. Of course, it's still good value for money if it can deliver. Thermal Fluctuations and Heat Haze can indeed be a problem when using long lenses on subjects a long way away. I've experienced this myself and yet I find the heat shimmer is very consistent in each frame and you can see this shimmer when playing back images or video. I think it's a good assumption that heat haze might affect AF but that it's more likely that the combined focal length on the R7 is producing contrast at that time and place that produces problems that Canon have observed in the past when coupling extenders with certain lenses. It's also why Canon expressly don't recommend stacking Extenders because they claim that contrast is then impacted to the point where even the optical coatings don't produce enough contrast for the AF to be reliable.
.
To the birders and long-lens users out there, how much of a problem has heat shimmer presented to you?

Almost zero problems > because in spite of the fact I shoot with an 800mm lens on a crop body for an equivalent of 1280mm, I HATE to shoot stuff a long ways off. I like small birds in my face ! For me, I'm trying to shoot birds from 20-25ft.... maybe 30 or 40ft if its a larger bird. Okay, 60 or 75ft if its a really big bird.... but I don't shoot a lot of really big birds.

The only times I've ever had heat shimmer issues, was shooting on a colder day, from a warm car. Almost impossible.

I've dealt with it under certain conditions with distant subjects

When I see distant subjects, I immediately start thinking, okay, how can I get close enough to fill my frame with it ? If I bother to take a shot of it at all, from a lot farther distance, its mostly for a better ID later. As its never going to be a great shot, with a lot of detail, which anyone will ever see.

when using long lenses, especially with APS-C and especially with Extenders. It's normally not a problem and never seems to present itself as an issue with a FF sensor (for me at least). But I'm presently of the opinion that in this instance it may come down to the lens design (aperture range coupled with focal length and high ISO) combined with APS-C sensors at times of the day when contrast is lower. The Eye Detect AF on the R-series cameras is particularly effective and is generally quite reliable on all models. But I feel that the use of this lens on an APS-C (giving around 1200mm) will push the boundaries of reliability if everyone is shooting at 800mm with an APS-C camera.
.
Duade is assuming the problem is Heat Shimmer but he leaves room for speculation or for people to suggest an alternative explanation. I'm not entirely convinced it's related to Thermal issues but I'm sure it could influence the results. I've seen other examples by birding photographers shooting close to the ground over rocks in the hot sunlight where they had no problems at all with this lens (see samples by OrmsTV). Reviewer Hugh Sweeny has also observed unacceptably soft images from this lens yet I thought they were close enough to being sharp in most of his examples. Though the contrast was higher when the shots were crisper. Anyone have any thoughts on the subject?

I follow Duade, and he is an "excellent" photographer. But he tends to not fill as much of his frames with bird, as I do. For that matter, most of the photographers I've seen fill less of their frame with bird, than I do. Which of course is just personal preference.

I've actually heard it said once about my style of bird photography.... "Just a bunch of 'yearbook' style bird photos, that get boring after a while' lol "HEY now ! I resemble that statement" ! lol I'd like to describe my bird photos as a photo record of all the beautiful / cool birds that I've seen. I guess I am kind of a "birder" I just place more weight on an excellent photo, and birds which are either really colorful, contrasty, or unique, or some mix of the three.

Anyway, I think its funny when I'm out in the field and non photography folks see my camera setup and often say, "Wow ! I bet you can shoot stuff a long ways away" ! To which I always reply, "Well not if I can help it" lol

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--
Every day in the field is a blessing. Nice photos, of beautiful birds and wildlife are just a bonus.

Chris Wolfgram ✝️

Explore Chris Wolfgram ✝️’s 1,110 photos on Flickr!

www.flickr.com

No time or attention given for negativity or trolls.

 

[BirdShooter7]

Yes I find the needs good light comments a bit amusing myself. EVERY lens needs good light to make beautiful photos. If the Leigh’s not good or the subject is too far away or any number of other unfavorable conditions exist it’s going to have a negative impact on your results. That’s the whole reason we try to be out in ideal conditions and be at an ideal distance from the subject and try so hard for an ideal background…

 

[Chris Wolfgram]

Yes I find the needs good light comments a bit amusing myself. EVERY lens needs good light to make beautiful photos.

Good light yes Bright light, rarely

I'm sitting here in my blind right now, and the clouds are coming and going. At 1:45 without clouds, it's just too darn harsh.... Bring on those clouds, and that awesome diffused light !

I've taken about 3000 shots though... 2000 with the 200-800, and 1000 with the 800 F11....

If I don't get some more clouds, I might have to wait until the sun gets low enough to blocked from my perches...

If the Leigh’s not good or the subject is too far away or any number of other unfavorable conditions exist it’s going to have a negative impact on your results. That’s the whole reason we try to be out in ideal conditions and be at an ideal distance from the subject and try so hard for an ideal background…

--
Every day in the field is a blessing. Nice photos, of beautiful birds and wildlife are just a bonus.
https://www.flickr.com/photos/161603079@N02/page1
No time or attention given for negativity or trolls.

 

[Victor Engel]

I have not read through the thread yet, but you should realize that "heat shimmer" effectively changes the lens formula by adding more elements in front of the lens connected to the camera. It does have prefocus buttons, does it not? That might be a good use case for it.

I guess he may not have noticed it, but there was a lot of shimmering on his moon clip also.

--
Victor Engel

 

[drsnoopy]

I have not read through the thread yet, but you should realize that "heat shimmer" effectively changes the lens formula by adding more elements in front of the lens connected to the camera. It does have prefocus buttons, does it not? That might be a good use case for it.

I guess he may not have noticed it, but there was a lot of shimmering on his moon clip also.

In my experience, atmospheric “shimmer” is not possible to correct by manual focusing, pre-focusing, or the best AF on the planet, because it’s not a focusing issue. It’s due to turbulence between layers of air with different density due to temperature differences. Air has its own optical properties including refraction and reflection. These distort and diffuse the image, and can occur at hot or cold temperatures. If the conditions are causing shimmer, no focusing techniques - or optical excellence - can overcome it. Either get closer (much closer), come back another day, or accept the result. Sometimes it can even add to the image - emphasising the distance!

You would see exactly the same through your binoculars - no matter how expensive - it’s not a function of the camera or lens.

 

[duncang]

.
I've seen some reasonably good images from this lens so I'm not concerned with it's results. Some reviewers were happy with it and it's clearly going to be popular for the additional zoom on the far end, especially for well lit wildlife photography during daylight hours.
.
Duade Paton (see embedded video below via YouTube) has been working with the new and upcoming Canon RF 200-800 mm F6.3-9 IS USM Lens and has a recent video up showing he has experienced a not-so-insignificant number of super-soft images from this lens that he described as "completely unusable" when doing his review for the lens. You can see some of his examples here. This guy is an experienced photographer who specializes in birding and he's familiar with most equipment out there. The video he posted also shows some Live View footage of the AF struggling to remain locked on the subjects repeatedly.
.
He mentions that another photographer, who is a friend, appeared to experience the same issue at another time and place. I would agree that heat shimmer could affect some images but not quite with the same consistency we're seeing in the examples he posted as these are very soft and appear to be out of focus. Images on his video show an out of focus subject where nearby insects appear to be in focus... suggesting it's not atmospheric distortion ruining shots.
.



.
I suggested that the failure to focus properly is not necessarily connected with "heat haze" but was more likely related to the unusually long focal length of the 200-800mm lens combined with narrow aperture, resulting in a significant change in contrast to the scene. This is something Canon has previously addressed with their EF and RF Extenders by adding a tiny microprocessor that literally slows the AF down to increase exposure and AF accuracy from the lens. The 2x Extenders are programmed to slow down AF by 75% and the 1.4x Extenders slow the lens down by around 50%. This is by design and its to allow more accuracy with the AF. Canon were well aware of contrast with certain apertures and focal lengths combining to hamper AF.
.
When combined with an APS-C sensor (like that of the R7), it would appear this lens is perhaps punching above its weight and paying the price in certain lighting conditions, depending on the distance to the subject. Of course, it's still good value for money if it can deliver. Thermal Fluctuations and Heat Haze can indeed be a problem when using long lenses on subjects a long way away. I've experienced this myself and yet I find the heat shimmer is very consistent in each frame and you can see this shimmer when playing back images or video. I think it's a good assumption that heat haze might affect AF but that it's more likely that the combined focal length on the R7 is producing contrast at that time and place that produces problems that Canon have observed in the past when coupling extenders with certain lenses. It's also why Canon expressly don't recommend stacking Extenders because they claim that contrast is then impacted to the point where even the optical coatings don't produce enough contrast for the AF to be reliable.
.
To the birders and long-lens users out there, how much of a problem has heat shimmer presented to you? I've dealt with it under certain conditions with distant subjects when using long lenses, especially with APS-C and especially with Extenders. It's normally not a problem and never seems to present itself as an issue with a FF sensor (for me at least). But I'm presently of the opinion that in this instance it may come down to the lens design (aperture range coupled with focal length and high ISO) combined with APS-C sensors at times of the day when contrast is lower. The Eye Detect AF on the R-series cameras is particularly effective and is generally quite reliable on all models. But I feel that the use of this lens on an APS-C (giving around 1200mm) will push the boundaries of reliability if everyone is shooting at 800mm with an APS-C camera.
.
Duade is assuming the problem is Heat Shimmer but he leaves room for speculation or for people to suggest an alternative explanation. I'm not entirely convinced it's related to Thermal issues but I'm sure it could influence the results. I've seen other examples by birding photographers shooting close to the ground over rocks in the hot sunlight where they had no problems at all with this lens (see samples by OrmsTV). Reviewer Hugh Sweeny has also observed unacceptably soft images from this lens yet I thought they were close enough to being sharp in most of his examples. Though the contrast was higher when the shots were crisper. Anyone have any thoughts on the subject?
.

This is not a lens issue - it will affect every lens shooting over similar distance, and it doesn't have to be more than 10 meters to be affected.

Yes, heat shimmer is not so much affecting the focus as affecting the light and preventing anything sharp.

I was out a few days ago on a seemingly beautiful morning to find the same thing with my 600 f/4. Morning air was cool and water was warm ruining any chance of a decent image even very high up. Bird close or far made no difference all ruined by the atmospheric conditions.

When the sea breeze blew in things improved but the sun was already too high. Some days that's just how it goes.

 

[boldcolors]

I wonder if trying different filters on the lens would be a worthwhile experiment? I know digital sensors have UV filters but I remember I've read "somewhere" that the filterfactor can vary a lot depending on producer/sensor.

Sometimes when I am bored I like to experiment with different lens filters most people have dumped on the used market since the digital era started but some of them actually have an impact even today. When I put a blue filter (80A) on the lens in daylight I get slightly better contrast and a bit more saturation already in the RAW file. Maybe It COULD help the AF system, not sure.

Experiment 1 would be a very good HAZE filter I reckon.

 

[Greaves]

How would a filter help? The problem arises - as stated numerous times - due to moving columns of air between the lens and the subject. It has absolutely nothing to do with the lens. Indeed, putting a filter on the lens will only make matters worse by adding yet another element to degrade the image.

the secret lies in shooting at times when thermal currents are not so active or in severely reducing the distance between lens and subject.

 

[SteB]

It's very little to do with the lens, except its focal length. The claim that the insects flying around were in focus is mistaken (they're not, it's more contrast with them being backlit). If you look at the surface water, mud and plants, none of them are in focus, even on the sharpest focal plane. This is the most useful guide to atmospheric disturbance. If you have ground detail in the image, look for the focal plane, of where it all comes into sharpest relief. If even that is fuzzy, you know it's either atmospheric disturbance, or camera/lens movement.

I spend a lot of time, on a very wide open peat bog. You can see for up to 2 miles or more, especially from the observation platform. There is often a "heat haze", probably caused by the dark bare peat, and black body radiation i.e. it heating up and transmitting infra red, in direct sun. But heat haze is a misleading term, because you can get this heat shimmer in direct sun, even when air temperatures, are below freezing.

This isn't confined to camera lenses, but you get the same through high quality binoculars, and highly corrected spotting scopes. It makes observing anything at distance impossible, when it's like that. It will ruin sharpness in photographs, even over relatively short distances of 10-20m.

Of course, AF is going to struggle to lock on. This shimmer is constantly varying. For record purposes, I often take a lot of images, because it is surprising how much variability there is from one second to the next.

I have seen a few claims, with comparisons, that appear to show high quality primes are effected less than zooms. But I am sceptical, because as I say, if you take a series of shots over a longer period, you find great variation over how much the image is degraded. So it apples and not being compared to apples, as the shimmer constantly varies, and there is no way of predicting when it will be worse.

Likewise, someone discovered that removing the lens hood reduced the effect of shimmer, indicating the air in the space of the lens hood was heating up.

Overall, though, it's just something you have to live with. Wait for the sun to go in, or turn to flying birds, as this has less impact on them, especially when they are higher up. Self-evidently, the further away the subject is, the longer the focal length, the greater the effect will be magnified. As Duade demonstrates, this also happens over water, which I've experienced. It's not a lens model thing.