Direct comparison 800mm f6.3 vs 600mm f4 FL

[ChrisM]

It's entirely plausible that your copy was defect in some way. In fact, I assume it was.
It could have happened during transport, or it could be a combination of failing standards during assembly for your particular copy, after which the inevitable impacts during handling/transport knocked something out of alignment.
Or it could be a bad VR mechanism or focus group/motor. There are so many things that could possibly be wrong.

Fact is, that the image threads on the Z800PF are full of great images in a variety of circumstances.

Why not get another copy? If you then experience the same issues, I can understand it leaving a bad taste. Luckily, there are things like return policies and warranty.
You should not have to pay 7000,- for a lens producing hazy soft images.

 

[foxysport]

It's entirely plausible that your copy was defect in some way. In fact, I assume it was.
It could have happened during transport, or it could be a combination of failing standards during assembly for your particular copy, after which the inevitable impacts during handling/transport knocked something out of alignment.
Or it could be a bad VR mechanism or focus group/motor. There are so many things that could possibly be wrong.

Fact is, that the image threads on the Z800PF are full of great images in a variety of circumstances.

Why not get another copy? If you then experience the same issues, I can understand it leaving a bad taste. Luckily, there are things like return policies and warranty.
You should not have to pay 7000,- for a lens producing hazy soft images.

I totally agree with the last point--as for getting another one, I think I'll take a break and perhaps rent first. Thanks for the advice though!

 

[EricBowles]

There were admittedly a few cases where slow SS was uncalled for, but I was mainly following that advice to stay low SS and erred too much but look at that gull above--it is very static, nothing is happening, the focus is dead on the eye, and I get 0% success? About the technique, if I get sharp photos with a 600mm f4.0 FL that is 1.5 kg heavier, why would I struggle with the lighter and shorter lens like this 800mm f6.3?

Was the gull also a deep crop? Did you need any exposure adjustment in post processing?

 

[Ralph]

If you are referring to the buzzard taken with a 600mm lens, for sure there was atmospheric distortion present. The distance was around 200m and a warm clammy day as well.

In reference to shutter speed I’m referring to all the shots.

 

[foxysport]

Eric, Ralph, will reply later tonight, thanks!

 

[MarkB]

The above photos are OK but the keepers rate was very low. However, this one below is difficult to explain: the black-headed gull was right in front, the focus found the eye 100% of the time, and this is the "best" result. Pretty awful. Nuthatch is pretty poor as well.
View attachment 86599


View attachment 86601
View attachment 86602
And finally, this buzzard was pretty high, about 75 meters perhaps, but this is the _best_ photo above. All of about a 100 focused on the bird with no issues.

I'm 5% close to returning this lens tomorrow.

Seems to me that the shutter speed is too low to capture sharp shots of moving birds. Yes, one has to have good light with the 800, for lower light situations the 600 wins, and it is sharper as a bare lens, but as Steve's tests show, the 800 is just about as sharp as the 600 with the 1.4x. I recently shot Sandhill Cranes and in the early morning, with necessary slower shutter speeds, the 800 was producing results similar to what you have above, but once I got good light the results were great. Shot below is cropped, so some sharpness lost, but only one I could find that was small enough to upload here.

 

[doclrb]

I greatly appreciate the technical points raised by Mr. Bowles and others. As a simple user of the 800 PF I find it no less than phenomenal. This entire thread bears rest resemblance to a benefit/cost ratio discussion.

And these types of judgements are biased by human nature. And as my Major Professor stated years ago, impartiality in judgement is not possible because judgements are influenced by values.

So, let’s consider this discussion from two perspectives, noting that even the less expensive lens of the two is still beyond the means of many, and those that are able to expend funds at these levels, should be grateful for their circumstances, and not necessarily to a particular deity. That having been said:

1. You get what you pay for! Many believe the PF series offers value beyond its price, but that’s an individual judgement.

2. Let’s not forget buyer’s remorse. Human nature is such that if one had purchased an expensive product (most any F4 tele) and a less expensive potential alternative is released as technology improves, there may be temptation to prove to oneself that the sunk costs were justified.

Offered Respectfully,

Les

 

[Calson]

Why not compare shots taken with the 800mm at f/6.3 with the 600mm with the teleconverter engaged and a focal length of 840mm? This would be the relevant comparison of image quality shooting hand held between the two lenses.

I can hand hold my 800mm PF lens but know I cannot do so with the 600mm TC lens. Also a little matter of spending $16,000 versus $7,000 for a lens. And there is the matter of alternative lenses for 600mm view angle and image magnification as with the 600mm PF that sells for less than $5,000 and weighs 3.2 lb. I can see more value in having the two PF lenses and spending a total of $12,000 and having a lot more flexibility in shooting when not needing to carry around a tripod and gimbal head or shoot in places like from a small boat where using a tripod is questionable at best.

 

[ARClark]

View attachment 86527

View attachment 86528

These charts mirror my experience in terms of sharpness well on these lenses.

I don’t have a 600E FL, but I do have the 500E FL. And I have the 800 PF. I’ve photographed birds with both lenses and TCs on a Z9 and Z8. While I would rate the 500E a bit sharper, I’ve found IQ of the 800 PF to be about on par with 500E and a 1.4x TC (and better than the 500E/1.7x TC combo), but with slightly busier bokeh in some situations. Overall, I’ve found the 800PF to be an excellent lens for small bird photography. I haven’t had much opportunity to shoot BIF with it.

I found the Photography Life review of this lens to be an outlier and not an accurate assessment of the lens’ capabilities, regardless of the above MTF performance results.

Below is recent shot of a pine warbler at roughly 30 feet. The first picture just shows the original image and the relative size of the bird within the frame. The second is a 100 percent enlargement of a crop of just the bird with no processing other than slight brightening and compression of the JPEG to meet the forum's image size limitation. I personally find the ability of the 800 PF to render feather detail to be excellent.

You can only see EXIF info for this image if you are logged in.

You can only see EXIF info for this image if you are logged in.

The following shot of a bluebird is from a similar distance but photographed with the 800 PF and 1.4x TC. This one has been sharpened and processed for noise, but it does demonstrate the capability of this lens and TC to render pleasing IQ and excellent detail.

You can only see EXIF info for this image if you are logged in.

 

[foxysport]

Just for reference, I hand hold 95% of the time my 600mm f4.0 FL with no TC, with TC1.4, and very frequently, with TC1.7.

First, regarding Eric's question, the seagull crop was just over 100% and the original (unintentional) bias of 0.7 was reversed with a -0.75 in post.

To update everyone, there was a Wildlife day at Park Cameras in England today with reps from all major manufacturers present. I also had an opportunity to have my lens returned. I have reserved a fresh copy of 800mm f6.3 now but not yet paid or collected. I have had an opportunity also to shoot with that reserved copy as well as with the same lens from the Nikon stand with my trusty Z9, along with my own 600mm FL being also onsite.

I have primarily been able to photograph people from a distance obviously. My observations as well as the Nikon guys observations are as follows. The new reserved shop copy is equivalent to his own from the stand. The photos I took were about par with what he would expect. The photos I showed from this forum are _not_ what he would expect, period. The sample I had is faulty and will have to go back to Nikon.

The portraits I've been taking with all three lenses: 2 copies of 800mm f6.3 and my 600m FL--in my opinion now--are on par between the two 800mm copies, but I would take the 600mm rendition any day, with colour, texture etc to my eye, top notch. Cannot reproduce these here sadly, so you'll have to trust my word as well as Nikon's guy words that 600mm, even FL, would be "obviously" better.

I had a chance also to play with a 600mm f4.0 TC Z, and it is without any doubt my key replacement target for the FL. Having said that, most likely, I will proceed with this purchase of the 800mm and if it holds up well, especially for medium distances and sub-par conditions, I'll keep it and postpone the 600mm TC Z purchase, otherwise, the latter goes up the list, and hopefully, will be something I can use as my go-to lens shortly.

I'll leave you with a couple of in-flight shots here from the birds of prey display during the Wildlife day.

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You can only see EXIF info for this image if you are logged in.

 

[ajrmd]

I don’t have a 600E FL, but I do have the 500E FL. And I have the 800 PF. I’ve photographed birds with both lenses and TCs on a Z9 and Z8. While I would rate the 500E a bit sharper, I’ve found IQ of the 800 PF to be about on par with 500E and a 1.4x TC (and better than the 500E/1.7x TC combo), but with slightly busier bokeh in some situations. Overall, I’ve found the 800PF to be an excellent lens for small bird photography. I haven’t had much opportunity to shoot BIF with it.

I found the Photography Life review of this lens to be an outlier and not an accurate assessment of the lens’ capabilities, regardless of the above MTF performance results.

Below is recent shot of a pine warbler at roughly 30 feet. The first picture just shows the original image and the relative size of the bird within the frame. The second is a 100 percent enlargement of a crop of just the bird with no processing other than slight brightening and compression of the JPEG to meet the forum's image size limitation. I personally find the ability of the 800 PF to render feather detail to be excellent.

View attachment 86700

View attachment 86701


The following shot of a bluebird is from a similar distance but photographed with the 800 PF and 1.4x TC. This one has been sharpened and processed for noise, but it does demonstrate the capability of this lens and TC to render pleasing IQ and excellent detail.

View attachment 86702

I think this is fairly representative of the 800 f/6.3’s performance. Generally, the bokeh is fine unless there are backlit, specular highlights and then the “coffee beans” can appear.

 

[lisam]

I don’t have a 600E FL, but I do have the 500E FL. And I have the 800 PF. I’ve photographed birds with both lenses and TCs on a Z9 and Z8. While I would rate the 500E a bit sharper, I’ve found IQ of the 800 PF to be about on par with 500E and a 1.4x TC (and better than the 500E/1.7x TC combo), but with slightly busier bokeh in some situations. Overall, I’ve found the 800PF to be an excellent lens for small bird photography. I haven’t had much opportunity to shoot BIF with it.

I found the Photography Life review of this lens to be an outlier and not an accurate assessment of the lens’ capabilities, regardless of the above MTF performance results.

Below is recent shot of a pine warbler at roughly 30 feet. The first picture just shows the original image and the relative size of the bird within the frame. The second is a 100 percent enlargement of a crop of just the bird with no processing other than slight brightening and compression of the JPEG to meet the forum's image size limitation. I personally find the ability of the 800 PF to render feather detail to be excellent.

View attachment 86700

View attachment 86701


The following shot of a bluebird is from a similar distance but photographed with the 800 PF and 1.4x TC. This one has been sharpened and processed for noise, but it does demonstrate the capability of this lens and TC to render pleasing IQ and excellent detail.

View attachment 86702

We don't get Pine Warblers in the UK and such a lovely looking bird. My favourite is the Robin but I can't get shots like yours but i'll keep trying.

 

[cr_wildlife]

I have both the 600mm f/4 TC and the 800mm f/6.3 PF. The advantages of the 600mm: 1) f/4.0 wide open, 2) built in TC, which to quote Steve Perry "is a game changer", 3) shooting with the TC engaged, f/5.6, which is an advantage, not not much of one, 4) super sharp without and with the TC engaged, 5) improved backgrounds. Disadvantages of the 600mm: 1) cost, way, way more expensive, 2) weight, as others have pointed out. Hard to hand hold for long. Advantages of the 800mm: 1) weight, can hand hold when their is enough light to get the shutter speed up, 2) cost, 3) sharp (not as sharp, but good enough, especially in the center, as mentioned above) 4) reach without a TC, although the 600mm gets to 840mm with the built in TC. Disadvantages of the 800mm, 1) When pulling in an image from a distance, you are shooting through a lot of air, which increases the effect of heat refraction. This is a really big problem. Really can't use it in full sun, makes the time for early morning and late afternoon shooting very short, before the heat refraction prevents getting a sharp shot. I know, just shoot a long burst and hope for an undistorted shot. Works sometimes, but nowhere near always. I can't hand hold the 800mm with a Z 1.4 X TC (1120mm @ f/9) with the slow shutter speeds needed to get the ISO down and get a sharp image as the magnification of the subject also magnifies any slight movement, ruining the focus, so I have to use a tripod when using a TC. I can't hand hold the 800mm without the TC at slow shutter speeds without getting soft images due to movement, but the lens does work great on a tripod when you are shooting in the shade or other low light situations.
As usual, the decision comes down to what you want to do with the lens and what are you priorities. Is cost an issue? Are you looking to hand hold? Is weight an issue or do you always use a tripod? Do you want the best possible blurring of the background and the absolutely sharpest image possible?
Right now, I use the 600mm as my go to lens. I use the 800mm when I am walking around on days when heat refraction is not an issue (shooting in the shade, thin overcast).
I am not sure that I am being helpful, but the two lens are really different in functionality, and one simply needs to decide when and how you use a lens and decide from there. The 800mm is a really price performer, but the 600mm is the best lens I have ever owned.

 

[NLK Photos]

I have the 800 and LOVE it. Very sharp. The pigeon images above are not anything like the images I get with this lens.

 

[foxysport]

I have both the 600mm f/4 TC and the 800mm f/6.3 PF. The advantages of the 600mm: 1) f/4.0 wide open, 2) built in TC, which to quote Steve Perry "is a game changer", 3) shooting with the TC engaged, f/5.6, which is an advantage, not not much of one, 4) super sharp without and with the TC engaged, 5) improved backgrounds. Disadvantages of the 600mm: 1) cost, way, way more expensive, 2) weight, as others have pointed out. Hard to hand hold for long. Advantages of the 800mm: 1) weight, can hand hold when their is enough light to get the shutter speed up, 2) cost, 3) sharp (not as sharp, but good enough, especially in the center, as mentioned above) 4) reach without a TC, although the 600mm gets to 840mm with the built in TC. Disadvantages of the 800mm, 1) When pulling in an image from a distance, you are shooting through a lot of air, which increases the effect of heat refraction. This is a really big problem. Really can't use it in full sun, makes the time for early morning and late afternoon shooting very short, before the heat refraction prevents getting a sharp shot. I know, just shoot a long burst and hope for an undistorted shot. Works sometimes, but nowhere near always. I can't hand hold the 800mm with a Z 1.4 X TC (1120mm @ f/9) with the slow shutter speeds needed to get the ISO down and get a sharp image as the magnification of the subject also magnifies any slight movement, ruining the focus, so I have to use a tripod when using a TC. I can't hand hold the 800mm without the TC at slow shutter speeds without getting soft images due to movement, but the lens does work great on a tripod when you are shooting in the shade or other low light situations.
As usual, the decision comes down to what you want to do with the lens and what are you priorities. Is cost an issue? Are you looking to hand hold? Is weight an issue or do you always use a tripod? Do you want the best possible blurring of the background and the absolutely sharpest image possible?
Right now, I use the 600mm as my go to lens. I use the 800mm when I am walking around on days when heat refraction is not an issue (shooting in the shade, thin overcast).
I am not sure that I am being helpful, but the two lens are really different in functionality, and one simply needs to decide when and how you use a lens and decide from there. The 800mm is a really price performer, but the 600mm is the best lens I have ever owned.

To me, this contribution is very important. If I carry a tripod with me for 15 miles, the extra 1.5 kg with 600mm FL or even less with 600mm TC mean very little in relative terms. The whole point to me of an 800m is to hand-hold it, this is its raison d'être if you wish. If I get better photos with a 600mm, why would I compromise. Low-light is associated with a number of scenarios: morning/evening, forests/shade, northern/rainy skies, and high shutter speed--all are critical for truly interesting photos. If we need to tweak SS down to achieve a good result, it is not a real option.

Rachel Bigsby was presenting yesterday at the Wildlife day and not a single photo was taken with an 800mm. The lenses used were 20-70, 70-200, 400 f4.5, and 600mm f4.0 TC. She's just back from Antarctica and there was no hesitation to show a photo of hers handholding a 600mm.

Bottom line, still conflicted, may get a reserved copy of 800mm and take it for a critical spin, or just forgo the drama and get the FL replaced with a Z TC.

 

[ajrmd]

To me, this contribution is very important. If I carry a tripod with me for 15 miles, the extra 1.5 kg with 600mm FL or even less with 600mm TC mean very little in relative terms. The whole point to me of an 800m is to hand-hold it, this is its raison d'être if you wish. If I get better photos with a 600mm, why would I compromise. Low-light is associated with a number of scenarios: morning/evening, forests/shade, northern/rainy skies, and high shutter speed--all are critical for truly interesting photos. If we need to tweak SS down to achieve a good result, it is not a real option.

Rachel Bigsby was presenting yesterday at the Wildlife day and not a single photo was taken with an 800mm. The lenses used were 20-70, 70-200, 400 f4.5, and 600mm f4.0 TC. She's just back from Antarctica and there was no hesitation to show a photo of hers handholding a 600mm.

Bottom line, still conflicted, may get a reserved copy of 800mm and take it for a critical spin, or just forgo the drama and get the FL replaced with a Z TC.

Many people, myself included don’t want to hike with or be bothered to use a tripod (in spite of the advantages). With all due respect to Ms. Bigsby, in my neck of the woods 600mm is frequently insufficient. Then one has two options, hike all day with a 600 f/.4+tc or use an 800 f/6.3. At my age, every oz/gm matters and handholding a 600 f/4 or carrying one on my shoulders is a non-starter. Traveling with one isn’t fun either. So, if the f/4 fits, you need to make it part of your kits (timely, no?). For the rest of us, the 800 f/6.3 is a reasonable option. Worry less and enjoy nature/photography more!

 

[foxysport]

Many people, myself included don’t want to hike with or be bothered to use a tripod (in spite of the advantages). With all due respect to Ms. Bigsby, in my neck of the woods 600mm is frequently insufficient. Then one has two options, hike all day with a 600 f/.4+tc or use an 800 f/6.3. At my age, every oz/gm matters and handholding a 600 f/4 or carrying one on my shoulders is a non-starter. Traveling with one isn’t fun either. So, if the f/4 fits, you need to make it part of your kits (timely, no?). For the rest of us, the 800 f/6.3 is a reasonable option. Worry less and enjoy nature/photography more!

Just a cautious disclaimer, that was not an endorsement of any kind by Ms Bigsby, it is my own opinion and an observation--for what it's worth!

As for the above comment, I was specifically saying that _if_ I have to carry a tripod _with_ an 800mm 6.3 in order to achieve acceptable results, I am _not_ going to do it for the sake of using a lighter lens. That is all. Therefore, the only point I am seeing to an 800mm is extra portability, the difference being less than 900 grams--not much for some, and too much for others.

 

[thelordofthelight]

Do you have any image samples in good light, preferably with a minimal or no crop? Also may i ask if you have tested the lens with different VR modes and also VR turned off? Have you also tested the lens on a different camera body? There seems to be something wrong with either the Lens or even the camera..the reason i include the camera is because the sample images from the 600TC are also not pin sharp…Not sure if that is due to lower res images getting compressed in the website…A Quick Look at the 800PF images thread on Fred Miranda shows us the kind of images this lens is capable of producing. Also, the below review of this lens by Steve is a proof of how sharp the lens is.

 

[foxysport]

I've looked now at the last page of the 800mm thread on fredmiranda and I am not impressed at all. A bit of pinch and zooming on iPad and it is easy to see what is really going on there.

Despite all of this, I am still likely to get this lens and as I said, give it a chance to impress. By the way, I have no idea how to post here anything bigger than really tiny files. Oh and by the way, if the question was to me, I have an FL, not a TC--yet.

Also, I have a pretty rare, and now out of manufacturing, calibrated 8K monitor from Dell to view and edit the photos so I am not sure what are people using to actually compare the photos, but a phone or a tablet is really not enough.

And finally, good weather is a big bonus in the UK. I cannot stress enough that photography in poor lighting is what is necessarily a requirement. No sharp photos made in Florida are of any direct interest to me.

 

[Gov]

I have both the 600mm f/4 TC and the 800mm f/6.3 PF. The advantages of the 600mm: 1) f/4.0 wide open, 2) built in TC, which to quote Steve Perry "is a game changer", 3) shooting with the TC engaged, f/5.6, which is an advantage, not not much of one, 4) super sharp without and with the TC engaged, 5) improved backgrounds. Disadvantages of the 600mm: 1) cost, way, way more expensive, 2) weight, as others have pointed out. Hard to hand hold for long. Advantages of the 800mm: 1) weight, can hand hold when their is enough light to get the shutter speed up, 2) cost, 3) sharp (not as sharp, but good enough, especially in the center, as mentioned above) 4) reach without a TC, although the 600mm gets to 840mm with the built in TC. Disadvantages of the 800mm, 1) When pulling in an image from a distance, you are shooting through a lot of air, which increases the effect of heat refraction. This is a really big problem. Really can't use it in full sun, makes the time for early morning and late afternoon shooting very short, before the heat refraction prevents getting a sharp shot. I know, just shoot a long burst and hope for an undistorted shot. Works sometimes, but nowhere near always. I can't hand hold the 800mm with a Z 1.4 X TC (1120mm @ f/9) with the slow shutter speeds needed to get the ISO down and get a sharp image as the magnification of the subject also magnifies any slight movement, ruining the focus, so I have to use a tripod when using a TC. I can't hand hold the 800mm without the TC at slow shutter speeds without getting soft images due to movement, but the lens does work great on a tripod when you are shooting in the shade or other low light situations.
As usual, the decision comes down to what you want to do with the lens and what are you priorities. Is cost an issue? Are you looking to hand hold? Is weight an issue or do you always use a tripod? Do you want the best possible blurring of the background and the absolutely sharpest image possible?
Right now, I use the 600mm as my go to lens. I use the 800mm when I am walking around on days when heat refraction is not an issue (shooting in the shade, thin overcast).
I am not sure that I am being helpful, but the two lens are really different in functionality, and one simply needs to decide when and how you use a lens and decide from there. The 800mm is a really price performer, but the 600mm is the best lens I have ever owned.

Why is heat refraction a disadvantage of the 800 PF, but not the 600TC (600 and 840)? Wouldn't it be the same for both lenses at the same distance?

 

[StefanSC]

I've looked now at the last page of the 800mm thread on fredmiranda and I am not impressed at all. A bit of pinch and zooming on iPad and it is easy to see what is really going on there.

Keep in mind that most of those photos are resized, compressed by the forums and mostly edited for web display.
Also that the iPad does all kinds of weird and wonderful upscaling and processing of images it displays so they look nicer .

That being said, my strategy for figuring out if a lens is a good performer or not is to find high res images taken with that lens and look at what is there and what isn't there and what is wrong with the image (e.g: I know for certain species of birds how a proper sharp image of their feathers looks and how an over-sharpened one looks... if most images taken with that lens by most peeople are over-sharpened it hints to me that the lens is a somewhat poor performer).

Flickr can be a good resource as well as the italian site juzaphoto.com ... you'll need to register but they have plenty of samples from plenty of lenses.

Why is heat refraction a disadvantage of the 800 PF, but not the 600TC (600 and 840)? Wouldn't it be the same for both lenses at the same distance?

Maybe the PF elements have something to do with it? I dunno, but it seems that technology really doesn't like light bouncing around in weird ways .

 

[foxysport]

Speaking about the fredmiranda threads photos: check out the last page of the 600mm TC Z thread and the same for the 800mm 6.3 thread and compare--make sure the photos are fully expanded. Also, notice the quality of compositions and how rare these photographed events were, not just "sharpness".

 

[Calson]

If I lived in Florida then a 600mm focal length would be OK. But with the subjects I generally encounter in the west a 180-600mm with the 800mm PF is a better setup. In the Pantenal I used the 500mm PF with a TC-20 on the D850 and I needed a monopod to get a sharp images from a boat. It was not a matter of the weight but my ability to hold the lens still enough and of course with the D850 there was no in-camera image stabilization being provided. It would be quite different with the Z8 or Z9 cameras.

I have owned the 600mm f/4E and the 200-400mm f/4 and with both lenses I need a tripod. Others may be fine using these lenses hand held but it is too much for my body. If the 800mm PF did not exist I would have bought the 600mm f/4 TC. Fortunately the 800mm PF lens shipped first. If I needed a 600mm focal length lens I would be more inclined to get the 600mm PF lens based on my experiences with the 500mm PF lens.

I have found overall that the Z9 with its internal image stabilization combined with excellent subject detection that I no longer need to use manual autofocus override as in the past with my DSLR cameras. With manual focus override there was more of a need to support the lens on a tripod head and have both hand free.

Bottom line it comes down to the subjects and locations and the usual camera to subject distances that influence my own lens choices.

 

[foxysport]

If you love the 800mm lens, please go to the flickr group dedicated to it and post: https://www.flickr.com/groups/14783148@N24/.

 

[IngeKJ]

I don’t have a 600E FL, but I do have the 500E FL. And I have the 800 PF. I’ve photographed birds with both lenses and TCs on a Z9 and Z8. While I would rate the 500E a bit sharper, I’ve found IQ of the 800 PF to be about on par with 500E and a 1.4x TC (and better than the 500E/1.7x TC combo), but with slightly busier bokeh in some situations. Overall, I’ve found the 800PF to be an excellent lens for small bird photography. I haven’t had much opportunity to shoot BIF with it.

I found the Photography Life review of this lens to be an outlier and not an accurate assessment of the lens’ capabilities, regardless of the above MTF performance results.

Below is recent shot of a pine warbler at roughly 30 feet. The first picture just shows the original image and the relative size of the bird within the frame. The second is a 100 percent enlargement of a crop of just the bird with no processing other than slight brightening and compression of the JPEG to meet the forum's image size limitation. I personally find the ability of the 800 PF to render feather detail to be excellent.






The following shot of a bluebird is from a similar distance but photographed with the 800 PF and 1.4x TC. This one has been sharpened and processed for noise, but it does demonstrate the capability of this lens and TC to render pleasing IQ and excellent detail.

If the 500 with a TC on is on par with the 800 then the MTF charts would be quite accurate as the TC makes sharpness take a hit. I have the 800 myself. It is not as sharp as any of the FL-e superteles, but why should it be? Those cost at least twice as much, no expense spared on weight or price, and no PF elements.