Canon RF 800mm f/11 IS STM

Thanks, Levina! The only thing that concerns me with both extenders on the 800 f11 is that noise appears to increase with the apertures getting smaller. Even without an extender on the 800 f11 I had significant issues with noise while shooting late afternoon, perhaps an hour before sunset. It could be quality of the light at that time, but I was forced to use a shorter 100-400 or Sigma 150-600 to allow larger apertures. It seems it's always a trade-off when considering lenses.

Thanks, Mark! You're sooo right about them looking alike. Some birders here were hoping our Glossy turned out to be a White-faced...that would have been a Mega-rarity. And great shot of your WFIB!

steveb108 wrote in post #19222107
Thanks, Mark! You're sooo right about them looking alike. Some birders here were hoping our Glossy turned out to be a White-faced...that would have been a Mega-rarity. And great shot of your WFIB!

Here in Florida we have millions of white ibis and a fair number of glossies too. Occasionally one of the glossies turns out to be a white faced. Every gets pretty excited about it!!

I don't think I have knowingly seen one but I see lots of glossies including some nests!! No 800mm f11 photos though!!

steveb108 wrote in post #19222102
Thanks, Levina! The only thing that concerns me with both extenders on the 800 f11 is that noise appears to increase with the apertures getting smaller. Even without an extender on the 800 f11 I had significant issues with noise while shooting late afternoon, perhaps an hour before sunset. It could be quality of the light at that time, but I was forced to use a shorter 100-400 or Sigma 150-600 to allow larger apertures. It seems it's always a trade-off when considering lenses.

Not really sure if aperture is related to noise. Stopping down too much may result in diffraction, sure (and yield softer images), but generate more noise? I don't know. Maybe with narrower apertures and not increasing ISO speed you need a longer shutter speed, meaning more light comes in but also more noise? Something like that? I'm not a tech person and have no idea, Steve. Maybe John Sheehy will see this and respond.

I can't say I have noticed it with the 800/11, with or without extender. The difference in noise I notice in my files at equal ISO speeds seems to always be related to quality of light. Cropping too much also results in noise getting more visible. And when I'm shooting in low light, I still tend to shoot to the right of the histogram, if alone to preserve as much detail in the shadows as possible. I believe that is old school now, but old habits are hard to break...

Levina de Ruijter wrote in post #19222182

steveb108 wrote in post #19222102
Thanks, Levina! The only thing that concerns me with both extenders on the 800 f11 is that noise appears to increase with the apertures getting smaller. Even without an extender on the 800 f11 I had significant issues with noise while shooting late afternoon, perhaps an hour before sunset. It could be quality of the light at that time, but I was forced to use a shorter 100-400 or Sigma 150-600 to allow larger apertures. It seems it's always a trade-off when considering lenses.

Not really sure if aperture is related to noise. Stopping down too much may result in diffraction, sure (and yield softer images), but generate more noise? I don't know. Maybe with narrower apertures and not increasing ISO speed you need a longer shutter speed, meaning more light comes in but also more noise? Something like that? I'm not a tech person and have no idea, Steve. Maybe John Sheehy will see this and respond.

I can't say I have noticed it with the 800/11, with or without extender. The difference in noise I notice in my files at equal ISO speeds seems to always be related to quality of light. Cropping too much also results in noise getting more visible. And when I'm shooting in low light, I still tend to shoot to the right of the histogram, if alone to preserve as much detail in the shadows as possible. I believe that is old school now, but old habits are hard to break...

Levina, as I'm not particularly tech savvy either, I'll leave discussions of noise and light diffraction to those who know. I'll just default to IQ being improved by using lenses with larger apertures in certain cases, though of course there likely were other variables not fully tested.

A nesting female GHO and its dutiful male partner on standby from a nearby tree with a wary look....

With 1.4x @ 1120mm ISO 4000 and 6400

steveb108 wrote in post #19222102
Thanks, Levina! The only thing that concerns me with both extenders on the 800 f11 is that noise appears to increase with the apertures getting smaller. Even without an extender on the 800 f11 I had significant issues with noise while shooting late afternoon, perhaps an hour before sunset. It could be quality of the light at that time, but I was forced to use a shorter 100-400 or Sigma 150-600 to allow larger apertures. It seems it's always a trade-off when considering lenses.

What are you defining as "noise"? I've seen that term tossed around in different ways in this forum. Can you show an example, and list correct EXIF information?

I'd assume Steve's correlation between aperture and noise is simply due smaller aperture means less light, and thus one must boost iso to get the same shutter speeds. You know, its part of the reason why we've been buying fast glass all this time.

CyberDyneSystems wrote in post #19222324
I'd assume Steve's correlation between aperture and noise is simply due smaller aperture means less light, and thus one must boost iso to get the same shutter speeds. You know, its part of the reason why we've been buying fast glass all this time.

Perhaps the teleconverter takes takes some small portion of the light too. The new cameras seems to show great images at high ISO values.

I was using noise in a very broad sense to mean alteration of brightness and color in an image, manifested in large part by a grainy appearance...should have just stuck to IQ as I mentioned to Levina. I wish I were better-versed in the matters of noise and light diffraction, but alas.....

CyberDyneSystems wrote in post #19222324
I'd assume Steve's correlation between aperture and noise is simply due smaller aperture means less light, and thus one must boost iso to get the same shutter speeds. You know, its part of the reason why we've been buying fast glass all this time.

That was my first thought but I assumed Steve knows this too and looking at his latest shots in this thread, ISO speeds are not high, 2000 or less. For the R6 that’s not high and there should be little noise.

Pied-billed Grebe in breeding colors in display mode.

Levina de Ruijter wrote in post #19222182
Not really sure if aperture is related to noise. Stopping down too much may result in diffraction, sure (and yield softer images), but generate more noise? I don't know. Maybe with narrower apertures and not increasing ISO speed you need a longer shutter speed, meaning more light comes in but also more noise? Something like that? I'm not a tech person and have no idea, Steve. Maybe John Sheehy will see this and respond.

I can't say I have noticed it with the 800/11, with or without extender. The difference in noise I notice in my files at equal ISO speeds seems to always be related to quality of light. Cropping too much also results in noise getting more visible. And when I'm shooting in low light, I still tend to shoot to the right of the histogram, if alone to preserve as much detail in the shadows as possible. I believe that is old school now, but old habits are hard to break...

The question, I think, is "compared to what?". If you use 800/11 instead of 800/5.6, then you get more diffraction, more noise, and less background blur, AOTBE, just as if you took the same shot with an 800/5.6 lens, one at 5.6 and another at f/11 with the same shutter speed. If you use 800/11 instead of cropping from from 400/5.6, however, all the analog qualities are the same, the only differences being that the 800mm puts 4x as many pixels-on subject, which resolves the subject better. Yes, the diffraction blur, as measured in pixels, has twice the radius for f/11, but the subject is also twice as tall and wide, so the net effect of diffraction blur size relative to subject size is the same; you have the same analog subject-normalized diffraction. By sampling the subject with 4x as many pixels, though, the coarseness of the color filter array and the radius of the anti-alias filter halve in each dimension, relative to the size of the subject. What you get is pretty much the same as if you had used 400/5.6 on a a 20MP m43 camera, except that the RF800/11 seems to have nearly zero aberration, based on how impressed many people are with it. I don't know if the 400mm lenses typically used on m43 cameras are as low in aberration.

It's the same thing when you put TCs on the already "slow" 800/11, the diffraction gets larger, but so does the subject, for a net zero change in their relationship, ISO goes higher, but the subject is larger, making up for it, and the coarseness of the CFA and the radius of the AA filter both get even smaller and have less negative effect.

There is no generic loss in subject quality with maintaining the same entrance pupil (71mm in this case) with longer and slower options, when compared to cropping and shooting from the same distance; what you have to watch out for is loss of AF ability, darker sensor dirt, and any added aberrations from the TC (which are probably quite small with Canon's latest TCs). High-contrast edges with lighting high in invisible light may blur more with TCs, too, as they are optimized for visible light.

If you also get farther from the subject with a TC, your entrance pupil stays the same size, but it looks smaller to the subject because you are farther, which means more subject-level diffraction and noise, and your background gets less blurred relative to subject size, because it is less out of focus, plus the entrance pupil also looks smaller to the background, even if not as much smaller as it is to the subject. Also, when you get farther from the subject, the minimum usable shutter speed to keep motion blur small relative to subject size also increases, increasing subject-level noise.

When you don't get farther away, but use the TC as an alternative to cropping, you can increase shutter speed if you want, but it isn't as necessary as it is with being farther away, because subject-normalized camera motion blur has nothing to do with focal length, but rather, with distance. Think of a laser pointer attached to a long lens and pointed at the center of the frame; how much it moves around on a subject has nothing to with focal length, and everything to do with distance. So, even if you don't up your shutter speed for an added TC, you won't get subject captures worse than without the TC, and on the fraction of frames where there is the least camera/lens motion, you will get subject capture that is more detailed.

Levina de Ruijter wrote in post #19222344
That was my first thought but I assumed Steve knows this too and looking at his latest shots in this thread, ISO speeds are not high, 2000 or less. For the R6 that’s not high and there should be little noise.

It is easy to be on a witch hunt for noise that makes us dislike images just because we are magnifying or sharpening the results more than necessary. There's a huge difference between ISO 10,000 when you need to crop hard and sharpen to get a usable displayed subject size, and when the subject fills the frame with your desired composition, and you wind up downsampling it and then doing any remaining sharpening (usually very little after downsampling, if anything). The contrast and key of the scene, and the color of the ambient lighting also can make a huge difference with same ISO setting; almost every time you see someone post an example of how good their new camera is at high ISOs, the scenes usually have no large areas that are just a bit darker than midtones, as these are where noise gets obvious first. The darker areas can be rendered too dark to notice noise much, and the brighter areas have less noise to begin with.

Also, if a person does downsample images, but uses nearest neighbor, they are going to go "ouch" at lower ISOs, because nearest neighbor downsampling drops pixels, and loses captured light, increasing visible noise. This is especially problematic with low-res monitors, or viewing images shrunk to small windows on high-res monitors; the more the image is downsampled, the less original light or SNR is left in the displayed image. Let's say you look at R5 images on a 4K monitor, a 2K monitor, and an old 800*600 SVGA. Downsampled to fill the screen, that brings 45MP down to 7MP, 1.75MP, and 0.43MPs. This doesn't lose just resolution; it loses light and its SNR, and the noise is both increased, and sharpened chromatically due to the fact that chromatic noise is blurred at the original resolution due to demosaicing. The SVGA version loses over 99% of the light captured in the original 45MP!

Sensors have not been decreasing as much in measured noise as much as we'd like; for example, the 6D measures better than the R5 in DxO's DR graphs at higher ISOs, but they are going by over-simplified noise measurements that totally ignore noise character, especially in images displayed at small size. The R5 is much more usable at ISO 1 million for a 6x4 inch print or web image, because like most recent camera sensors other than the one in the 6D2 and RP, there is very little large grain or thick banding patterns to the noise, so while it may be obvious at high magnifications, at low magnifications it mostly disappears, like dithering in printed media disappears when you put down the magnifying glass or walk further from the media. Older sensors tended to have larger or "spatially correlated" noise patterns that still remained visible at small display sizes.

Mountain Bluebird, shot this morning. The 800/11 is working well for me, but I'm finding one has to pay attention to technique to get the best out of it. (And I'm not there yet! )

Photo from Archibald's gallery.
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