Sony a series: My depth of field is TOO shallow…

[Bray]

…said nobody, ever. Except me.

Hi, I’m a new to this forum, and hoping members might be able to shed light on a considerable bug-bare I have with my camera kit. Sorry this post is long, but I want to give you as much detail as possible. I shoot with a Sony a7s ii and an a6400, and mostly Sony G-series glass. Initially I bought the a7s ii for film, and that’s largely what I still use it for. As my interest in still photography and motion timelapses grew, I found the a7s ii a bit limiting for stills so I added the a6400 to my kit.

My problem is that I’ve always had trouble getting anything (other than landscapes) into sharp focus. For a long time, I assumed it was just a learning curve that I’d eventually master. But after several years of never-quite-sharp photos, I started to suspect it’s more to do with the kit than the operator. Today I tried a few tests with a focus chart, and it did confirm that on both cameras the area of acceptable focus is horrendously narrow. With some lens and aperture combinations, it’s actually impossible to achieve sharp focus. Do other Sony users experience this?

Some specifics:

When shooting landscapes and timelapses I typically use the wide end of the Sony 24-105 F4 G-series or the Zeiss 18mm F2.8 prime, and have no issues with focusing, even at maximum aperture. This seems obvious, given DOF is at its greatest at short focal distances.

Using the Sony 24-105 at its long end gives hit-or-miss results, but closing the aperture beyond F10 and cranking the shutter up to 1/400th or faster improves the chances of a sharp photo, when operating hand held. (But this then requires high ISO, and defeats the purpose of a lens that’s capable of F4 all the way through to 105mm. Like, alarm bells should be ringing at this point).

The problems really become clear when using tele lenses. I can get away with hand-held shots at F10 or above, and a shutter of 1/400th or faster, when at the long end of the Sony 70-200 F2.8 G-series, but oddly, the ability to resolve a sharp image is better with the a7s ii than the a6400. With this lens, the depth of field is shallower on the camera with the smaller sensor, which seems counter-intuitive. I thought the larger the sensor, the shallower the DOF.

The issue is amplified when I put the Sony x2 teleconverter onto the 70-200. Achieving focus whilst handheld is extremely difficult, if not impossible. This is tripod territory. The a7s ii handles the doubler much better than the a6400, but still has a devilishly narrow DOF. On the a7s ii, at wide apertures, focus can JUST be achieved if the camera is rock-solid stationary on a tripod. Closing down the aperture to F16 means that, for example, both of the subject’s eyes might be in focus (if I’m shooting from a tripod and the subject is still). When shooting birds, I typically have to shoot at F22 to have any chance of getting a sharp image. This really doesn’t sound right.
And when this lens & doubler combination is put on the a6400, achieving focus is almost impossible. With a tripod and 2-second shutter delay, I could JUST achieve sharp focus at F22. At F4.5, the DOF was so thin it seemed to be non-existent. I simply couldn’t get a single point of the chart into focus. Perhaps the optics of the 70-200 (and doubler) just aren’t compatible with a6400.

Filming small birds with long-lens stills glass on a locked-off tripod is pushing the limits of the gear, I know, and I long assumed the shallow DOF was just one of those limitations. But that I can’t get sharp STILL IMAGES with stills glass really has me scratching my head. To the point where I’m wishing I hadn’t invested so much into E-mount lenses, and had gone down the micro 4/3 track instead. Is that what it takes to get sharp images?

[Stagecoach]

Hi and welcome to the forum.

Firstly, are you certain you are not mixing 'Shallow depth of focus' with 'Sharpness of the focal plane'.

My other initial thought is how are you focusing? Are you using 'single point' (single point centre is generally the most accurate) or in a 'Auto' focus mode.

[Manfred M]

You make a few statements that suggest to me that you are not 100% clear at to how depth of field works. Depth of field is independent of your camera's focal length. Aperture and sensor size do factor in.

Could I suggest that you read an excellent article on the subject here:

https://www.cambridgeincolour.com/tu...h-of-field.htm

When you focus on a subject, there is only a single focal plane that is parallel to your camera's sensor. Anything on either side of that plane will get softer until you hot a point where it no longer seems to be sharp enough. This is defined by the "Circle of Confusion". The circle of confusion is dependent on how much the image has been magnified and your viewing distance, so if you are "pixel peeping" something will look less sharp than if you are viewing the image at a reasonable distance (usually a minimum of the diagonal of the image).

Stopping down improves depth of field, but diffraction starts to set in at smaller apertures and there will be overall softening of the image.

Often it is best to post the images you are having issues with here so that we can see what you are.Directions on how to do so are shown here: HELP THREAD: How can I post images here?

The internal CiC system does not host large images, so linking to external image hosts, for instance Flickr, works a lot better,

[Bray]

Hi guys, thanks for your prompt messages. Hopefully I can clear things up a little more...

@Stagecoach
No, I've been reading for the last few days about depth of field. I know I'm using the right term, and not mixing it up with 'sharpness of focal plane' (although, in my final example, using the 2x teleconverter with the 70-200 on the a6400 at F4.5, the DoF is so shallow that there is no sharpness at the focal plane). The examples in the link to CiC's article on DoF that Manfred provided are exactly what I'm talking about: there should be a distance in front of and behind the focal plane, where the image is acceptably in focus (ie. the DoF). My problem is that when I use anything but a wide lens, this area is horrendously thin, making it exceedingly difficult to focus.

Mostly, I focus manual. Auto focus on a7s is pretty bad. I have more luck with autofocus on the a6400, if I'm keeping the lens somewhat wide, and usually have the Focus Area set to Wide. But autofocus is useless on the a6400 as soon as I start using longer lenses. I just have to focus manually.

@Manfred
Thanks for sharing this link on DoF. It confirms that DoF is indeed my issue, even if I'm perhaps not explaining it in the right terms. I think the best way I can describe my issue is as I did for Stagecoach. There's just not enough area fore and aft of the focal plane that's 'acceptably' in focus. And example: even with the aperture closed, the DoF can be so narrow that one of the subject's eyes will be in focus and the other won't be! I'll have a look and see if I can find a photo that demonstrates this..

Regarding focal length not affecting DoF... I believe it actually does. I was taught this at film school, I've experienced it myself when switching lenses, or even just going from wide to long on the same zoom lens. And numerous articles on the net say it's a factor. Such as this one from B&H (about 3/4 of the way down).

The Circle of Confusion is a concept I've only just come across in the last few days and I'm still getting my head around it! It may take several more reads for it to stick in my brain!

[Stagecoach]

I know I'm using the right term, and not mixing it up with 'sharpness of focal plane' (although, in my final example, using the 2x teleconverter with the 70-200 on the a6400 at F4.5, the DoF is so shallow that there is no sharpness at the focal plane).

If there's no sharpness at the focal plane (wherever it is) that is due to degradation caused by the 2x TC, or, camera/subject movement, it has nothing to do with DoF.

The examples in the link to CiC's article on DoF that Manfred provided are exactly what I'm talking about: there should be a distance in front of and behind the focal plane, where the image is acceptably in focus (ie. the DoF). My problem is that when I use anything but a wide lens, this area is horrendously thin, making it exceedingly difficult to focus.

That's where a good AF system helps

and usually have the Focus Area set to Wide.

I'm not familiar with the Sony focus system but as mentioned previously for best AF a single point is preferable and provides best accuracy when using wide apertures with shallow DoF

[revi]

@Bray:
What kind of unsharpness do you see?
Your remarks about needing at least 1/400s when shooting hand-held, with 105-200 mm focal length makes me wonder if what you see isn't a movement problem.

Rule of thumb there is that your shutter speed should be faster than 1/(focal length), and I noticed I can have some trouble keeping
the camera steady enough even then.

And if you say that the autofocus is worthless, do you mean that it doesn't lock on, or that the resulting picture is unsharp?
I see the problem when doing close-up work, where the AF has trouble locking on the subject.

[Bray]

I've put together an album on Flickr with examples of photos where I feel the DoF should be deeper, based on the aperture setting. All camera setting details are in the photos.
https://flic.kr/s/aHsmNtvM73


This is probably the best example of my issue, where the aperture's reasonably closed, the focal plane can be seen, and nothing on either side of it has any sharpness.
[IMG]DSC09440 - crop by Braydon Moloney, on Flickr[/IMG]

Unfortunately few pics in this album are representative of me saying that I was shooting with a stopped down aperture to get a sharp image (Indeed, if the image came out sharp, there's not much point putting it up, is there!). It can certainly be argued that for some of these examples I really should have stopped down the aperture further, and it can also be argued that I should have had a faster shutter speed, or that I shouldn't have pressed the shutter until I'd attained absolutely perfect focus. Regardless, these examples show that one desirable element was in focus, whilst another was not - but really should have been sharper given the proximity to the point of focus. Hence, my believe that for some reason, my depth of field is consistently too shallow. I've shot on various Canon cameras in the past, and just never had this trouble.

[Bray]

@revi
Thanks for the rule of thumb regarding shutter speed (1/focal length). Some of the examples in the gallery adhere to this, some don't, and movement certainly might be a complicating factor in some of those photographs. But others, like 1/1600 for a focal length of 400mm should be safe, right?

Regarding the AF system, I have my greatest troubles when shooting with long lenses, or at the long end of the 24-105. The AF hunts and hunts and hunts and often doesn't find the subject. Or it settles on entirely the wrong thing, and then I have to make it hunt again. And I then miss the shot! It's not great on macro, either. It always locks onto the wrong thing there.

@ stagecoach

I'm not familiar with the Sony focus system but as mentioned previously for best AF a single point is preferable and provides best accuracy when using wide apertures with shallow DoF

I feel like I should be very familiar with the Sony focus system by now, but it's still a mystery to me. I've read the Sony instructional material so many times, and read so many blogs and watched so many YouTube tutorials on the subject, and they all say different Focus Areas are the best. Some say Wide is best with AF, some say Zone is the only way to go, some say Flexible Spot (which I believe is the equivalent of single point). But it's incredibly clunky trying to move the Spot into the right part of the frame, and by the time you've done it, the animal is gone. Admittedly, once the spot is over a sharp edge it does find focus, and repeatedly finds that focus. But it's such a faff to employ, and often animals don't have sharp edges!!!
I've tried all the AF settings, and Wide seems to work the best, at least with wider lens or short focal distances.

But I'm getting a bit off topic with my autofocus issues though!

[Stagecoach]

This is probably the best example of my issue, where the aperture's reasonably closed, the focal plane can be seen, and nothing on either side of it has any sharpness.

I see no obvious plane in that image that looks sharper than anything in front or behind it.

If I were you I would undertake some serious testing using tripod, remote, mirror up e.t.c to check for front/rear focusing error using a static subject. Three AA batteries on a 45 deg angle is a good start.

[Bray]

I guess that will be my job for tomorrow then!

[Stagecoach]

[B]Or it settles on entirely the wrong thing, and then I have to make it hunt again. And I then miss the shot!

But it's incredibly clunky trying to move the Spot into the right part of the frame, and by the time you've done it, the animal is gone. Admittedly, once the spot is over a sharp edge it does find focus, and repeatedly finds that focus. But it's such a faff to employ, and often animals don't have sharp edges!!!
I've tried all the AF settings, and Wide seems to work the best, at least with wider lens or short focal distances.

But I'm getting a bit off topic with my autofocus issues though!

Not off topic at all with Autofocus. If you are looking to get focus where you want it (baring front/rear AF errors) for shallow DoF work auto and wide is not the way to go.

Reduce the number of AF points allowing faster changing of them, preset it where you think it will be needed or frame looser are all options.

Edit;

Looking at the ones on Flickr I see nothing unusual in any of them, DoF is what it is and if you have not got your focus plane in the best position you will not be taking best advantage of the field of focus available at the set aperture.

Does you Sony software show 'focus point/points' selected, if so this can assist evaluation of results?

[DanK]

although, in my final example, using the 2x teleconverter with the 70-200 on the a6400 at F4.5, the DoF is so shallow that there is no sharpness at the focal plane)

No, you are still mixing up DOF with sharpness at the focal plane. DOF affects only how quickly focus is lost as one moves away from the focal plane. I do a lot of macro work where the DOF is so small that a photo of a single flower can require compositing 20 different photos, and each of those photos has a very shallow region where focus is pin sharp.

You have three things going on here:

1. DOF
2. AF
3. The sharpness of the image created by those lenses, if focused optimally.

1. DOF is what it is, for any given sensor, aperture, and distance. The brand of equipment has nothing to do with it. It's just math.

2. AF. You found problems while focusing manually, so the core problem isn't AF. But you have been given good advice about minimizing AF errors. My main camera has 61 AF points, if I remember right, but I can't recall ever letting the camera choose among them all. If you use a camera that has features like face AF, it'd a different matter, but if your AF system is simply looking for an area with contrast, it will often focus where you don't want.

3. The quality of the lens. There are a number of reasons why a lens might not be sharp when properly focused. I know nothing whatever about the Sony lens and extender you are using, but some extenders substantially degrade sharpness, particularly when used with certain lenses. The higher the magnification of the extender, the more likely it is to cause problems. I have a Canon 1.4X II, which is now out of date but was considered a pretty good extender in its day, but I can see some degradation when I attach it to my 70-200 f/4. The lens itself could have a problem, e.g., an element that has been knocked out of alignment. I know that my Canon L lenses can take quite a beating without damage, but it can happen.

So, I would forget about looking for something unusual with DOF. You won't find it. I would instead do what Grahame suggested: put the camera on a tripod and focus manually on something that has a diagonal line in the center so that you can see focus closer than and farther away from the focal plane. A yardstick is ideal for this. If you can't get a clean image focusing manually, then I would look for a problem with the equipment.

This same arrangement can be used to test your AF for front and back focus, but given that you have AF on the sensor, there shouldn't be any.

BTW, even with a tripod, there can be camera motion when you press the shutter if you don't have a remote release. i would make sure the center column is down and use a reasonable shutter speed.

[Manfred M]

Regarding focal length not affecting DoF... I believe it actually does. I was taught this at film school, I've experienced it myself when switching lenses, or even just going from wide to long on the same zoom lens. And numerous articles on the net say it's a factor. Such as this one from B&H (about 3/4 of the way down).

I can't remember how many times one of my professors made a mistake every now and then. I suspect one of my film or photography profs likely made the same mistake, but once one understands the math / physics, it becomes quickly obvious as to why this is not correct and the CiC article that showed the link to explains the math and physics as to why this is the case.

What is really happening is the degree of magnification that impacts DoF. If you want to test this yourself, it's quite easy. Take a shot, using the same camera, at the same aperture with two different focal lengths, but make the subject the same size in the image. Examine the two shots and you will find that the DoF is identical. The reason for the misunderstanding that focal length is a factor comes about because we tend to use a longer lens to "magnify" our subjects.

Also please remember that the CoC / DoF is impacted by image size and viewing distance. Look at an A2 size image from 30 cm distance and from a metre away, you the DoF will appear different.

[Manfred M]

Rule of thumb there is that your shutter speed should be faster than 1/(focal length), and I noticed I can have some trouble keeping the camera steady enough even then.

Carefully said, there are a number of underlying assumptions here that impact that rule of thumb. That rule was based on shooting a 35mm camera and making an A4 / 8" x 10" print held 30 cm / 1 foot away.

Change those variables, and that rule of thumb goes right out the window. What variables? Image stabilization, sensor size, final image size and viewing distance.

[William W]

I interrogated several of the images in the file to which you linked.

There is nothing remarkable apropos DoF.

***

As one example - Image of two adult females and one infant: Data: F/5.6; Sony6400; FL = 38mm.

Forensic investigation on what appears to be the full frame of that image, establishes that the SD (Subject Distance) is approximately 2100mm. At that SD with that gear, using CoC = 0.016mm, expected adequate DoF for a 250mm x 200mm image viewed at about 450mm will extend 300mm behind the Plane of Sharp Focus and 240mm in front of the Plane of Sharp Focus.

The Plane of Sharp Focus appears to run through or near the Left Eye of the Woman in the green dress.

The eyes of the child are at the least 240mm in front of that woman’s Left Eye, and due to the woman’s carriage of the child and the child’s angular presentation to the camera, it is reasonable to argue the child’s eyes are more than 240mm in front of that woman’s Left Eye.

Additional to that matter of interrogating DoF, the camera has capture Movement Blur of the woman in the green dress and movement of the Child. These is evidenced by trailing edge blur on the woman’s Right ear decoration and because the eyes are in relatively sharper focus the most plausible conclusion is that she had terminated her head movement before the Shutter was released.

On the other hand and albeit not that one movement indicator for the Child is conclusive, the combination of similar blur patterns on: the blue bow; the R Ear; and the L shoulder of the white dress leads reasonably to conclusively evidence that child’s head was moving downward and to camera left, whilst the shutter was opened.

Mentioning Subject Movement Blur is relevant, considering that the complaint regarding inadequate DoF references the Child’s eyes as not being in acceptable sharp focus.

The bottom line is: 1/160s was too slow for this shot.

In a shot like this one of the two women and the child, and if you HAD to pull that shot at F/5.6, then you’d be better to Lock Focus on the Child’s eyes, knowing that, in this shooting scenario of a multiple tight head shot you will have the greater amount of DoF behind, rather than in front.

In any case – I’d want to be at F/8 (at least, probably F/10) for that formation of three and have the Shutter at 1/320s, at the slowest, whenever there is an infant involved in the shot.

*

I see no evidence in any of the other posted images where the DoF is “too shallow”.

I do see evidence that Adequate Focus has not been attained in some images and also that some images have captured Movement Blur.

*

Prima facie it seems you are having issues with Focus and understanding (the limits of) DoF and how that plays into your choices of Aperture.

Additionally, I suggest that you rethink your processes for the selection of your Shutter Speeds.

I think that AF (if available on the lenses you're using) on Sony gear would be reasonably slick, if it is used correctly.

There’s been good general advice on how AF works. I suggest this be a primary area of development for you.

*

A x2.0 tele-converter on any zoom lens will show Image Quality Degradation, and you’re pulling some of those shots with the lens at its Maximum Aperture. I haven’t used the Sony 70~200/2.8, but I reckon that it is a big ask to plonk a x2.0 on it, and then use the lens wide open, and expect anything to be tack sharp.

Let’s just assume, for the sake of argument, that the Sony 70~200/2.8 and their x2.0 equates to Canon the 70~200/2.8 L MkII and x2.0MkIII, which is the absolute best 70~200 + x2.0 extender I have ever used - I’d never use that combination with the lens wide open.

I also advise to do a Tripod Test as Grahame has suggested.

There are many matters which you need to sort and the best way of doing that is in a logical order.

The reference in the CiC tutorial, (extract below) is spot on the money. This is the Axiom of DoF and is very useful in the field, especially for Portraiture. I expect that you misread, didn’t read or didn’t understand the bit that I have underlined. If you were taught different to this at film school, then you were taught wrongly – I’d actually be interested in which school, and which teacher(s), if that is the case.

WW

Footnote -
"CLARIFICATION: FOCAL LENGTH AND DEPTH OF FIELD
Note that focal length has not been listed as influencing depth of field, contrary to popular belief. Even though telephoto lenses appear to create a much shallower depth of field, this is mainly because they are often used to magnify the subject when one is unable to get closer. If the subject occupies the same fraction of the image (constant magnification) for both a telephoto and a wide angle lens, the total depth of field is virtually* constant with focal length! This would of course require you to either get much closer with a wide angle lens or much farther with a telephoto lens" (op. cit.)

[William W]

(RE - image of cockatoo post #7)

I see no obvious plane in that image that looks sharper than anything in front or behind it..

I concur.

That image is an aggressive crop of the original frame.

The (assumed) full frame of that image was one which I interrogated. No (subject) area of the original is in tack sharp focus.

First suspicions would be:

1. Focus Error
2. General Image Quality degradation caused by x2.0 extender
3. Both of above
4. Exacerbation of already poor IQ by aggressive crop

Additionally, there is evidence of Subject Movement Blur in both wings, but the body and head show none.

WW

[William W]

Specifically on the B&H Article -

. . . Regarding focal length not affecting DoF... I believe it actually does. I was taught this at film school, I've experienced it myself when switching lenses, or even just going from wide to long on the same zoom lens. And numerous articles on the net say it's a factor. Such as this one from B&H (about 3/4 of the way down). . .

I read it once through. The article is not "wrong", per se. It does make a common illogical conclusion, which I suppose is in fact 'wrong' in a sense. I' shall contact Henry.

In the part where it concludes, "If you want comparatively shallower DOF, use a lens with a longer focal length. A wider-angle lens will give you longer DOF" (op. cit.) there is above a diagram of two Photographers one using a W/A and the other using a Tele lens... and they're standing in the same position, relative to the Subject, ergo, they are making two ENTIRELY DIFFERENT IMAGES - non sequitur.

Where is one ounce of logic in comparing DIFFERENT images to make the conclusion that lenses control DoF?

This is a common non sequitur appearing on the www. Which leads to the view that there is some magical wand controlling DoF which is hidden in Telephoto Lenses - there isn't: Mathematics says so.

WW

[Manfred M]

Braydon - I'd like to direct you to Daniel Parent's Flickr page. He is one of the best wildlife / bird photographers that I personally know. We are both members of the same photography club and he is probably the best photographer at our club, especially when it comes to birds.

https://www.flickr.com/photos/11107124@N02/

He shoots a full frame camera and uses some very long lenses in his work. I know he owns a 600mm lens that he uses when birding and I think he borrows or rents longer lenses on occasion. He also shoots a Nikkor f/2.8 - 70-200mm for closer stuff.

The nice thing about Flickr is that you can see the shooting parameters (aperture, focal length, shutter speed and ISO). He told me that he shoots at high ISO quite often as that is easy to fix in post-processing. As he put it, you can't fix out of focus or motion blur in post, so why take a chance there.

The issue you may be running into is that mirrorless cameras do not autofocus as quickly as DSLRs. That is unfortunately an issue of contrast detect autofocus used in mirrorless cameras versus the phase detect in DSLRs. Contrast detect cannot tell whether it is focused in front of or behind the subject so it takes longer to hit the correct focus. With phase detect, this information is inherent with how the autofocus mechanism works, so the focus lock by the lens is very fast. The contrast detect has one major upside; front focus / back focus are never an issue as the focus calculation is made from sensor data, whereas with phase detect the focus mechanism is a separate module that can be off a bit for any specific lens. This can be fixed with the right testing technique and tools.

Birders and sports photographers generally do not use mirrorless cameras, but rather top of the line full-frame cameras; usually Canons and Nikons..

[rpcrowe]

The only Sony cameras I have used are the A6400, A6500, A6600 and A7iii. However, I have had pretty extensive experience with each of these cameras.

I have no problems focusing the A6400 despite the focal length of my lens. I shoot with lenses ranging from the 12mm f/2.0 manual focus Rokinon through the 28-75mm f/2.8 Tamron and 70-350mm f/4.5-6.3 E OSS lens and also use the 50mm f/1.8 OSS and the 85mm f/1.8 lens.

Given proper focusing procedures, I have never had the least problems with the auto focus of any of those lenses. The OP mentions "But autofocus is useless on the a6400 as soon as I start using longer lenses. I just have to focus manually". Perhaps in focusing manually, you might be throwing the whole system off. I never use manual focus when I have the Tamron or any of my Sony AF lenses mounted. The only time I use manual focus is when I have a manual focus lens on the camera...

I wonder if the problem might be camera shake or with the 2x TC, simply unsharp images due to the addition of a 2x TC.

I have occasionally tried a 2x TC on my Canon lenses but have been very disappointed with the results. OTOH. They were never sharp! I have been happy with a Canon 1.4x TC on selected lenses such as the 300mm f/4L IS. I have "heard" but, never had the opportunity to verify that the results from the latest 2x TC on the latest Canon 70-200mm f/2.8 lens are quite decent.

Here are two images using the A6400 in AF mode with the 28-75mm f/2.8 lens. Both are quite sharp...

70mm or 105mm equivalent at f/5


75mm or 112.5mm equivalent at f/3.5


And here is an image shot with the A6600 (basically the same AF focusing system as the A6400) using 350mm (525mm equivalent) wide open at f/6.3...


In each case my point of focus were the eyes of each subject.

The key to good focus on the A6400 or any A6xxx camera is "proper focusing procedure". These cameras have a very involved focusing system and it seems that it might be easy to have "operator error" when using the camera.

Mark Galer's Alpha Creative Skills free YouTube videos have some of the best information for making the complicated focusing system of the A6400/A6600 as simple as possible.

[William W]

. . . he is probably the best photographer at our club, especially when it comes to birds. He shoots a full frame camera and uses some very long lenses in his work. I know he owns a 600mm lens that he uses when birding and I think he borrows or rents longer lenses on occasion . . . He told me that he shoots at high ISO quite often as that is easy to fix in post-processing. As he put it, you can't fix out of focus or motion blur in post, so why take a chance there.
The issue you may be running into is that mirrorless cameras do not autofocus as quickly as DSLRs. . . .

Birders and sports photographers generally do not use mirrorless cameras, but rather top of the line full-frame cameras; usually Canons and Nikons..

I concur.

A great idea - it would benefit to interrogate many of technical aspects of the mentioned Photographer's works.

I suggest adding that to the list of potential issues/problems, investigations and corrections.

I reiterate, it is my view that the above touches on only one of many issues.

***

BIF is similar in many ways to fast action sport: I've zip experience with the former and many, many years with the latter.

It's common to be pulling ISO1600 or faster on a sunny day, simply to keep the Tv at or faster than 1/2000s when Sports action demands that: I have two mirror-less cameras, one Fuji, one Canon, both are excellent and I have no complaints regarding their performance. But I do know the limitations of both and neither would ever be used for serious captures of Sports Action.

I'll also refer you to a Bird Photographer whom I know – here is a [LINK] to a photograph typical of his skills and experience, yet not the very best of his work.

You'll see for this capture he's used long glass a 600mm prime and a x1.4 on it: importantly he's bumped to ISO 3200 so he can hold 1/4000s as the Tv AND he's not using the lens wide open, but stopped down one stop ... yet he has still captured some slight Subject Movement Blurr on the wing tips.

Here is another one [LINK] with Blue Sky as background – note he’s bumped to ISO2500 to allow him to pull Tv = 1/6400s AND he’s still not using his 600mm Prime Lens wide open when he has the x1.4 on it.

As mentioned the same techniques apply to sports action, [LINK], adapting a suitable Tv for each action’s momentum and direction and distance to the camera and the FL of lens used – in this shot, Tv = 1/1250s was (only just) fast enough: note that is a sunny day with hard shadows, mid-afternoon in Summer, shooting with the sun. (relevance below, in the next section)

*

The above leads into another observation whilst interrogating the images to which you linked: specifically the image of the Seagull over water -

Forensic interrogation of this image reveals quite a few considerations if not facts:

1. Post Production Artefacts suggest the original exposure is about 1 Stop under

2. Although there appears to be a "shadow" on the water, there are no hard shadows on the body of the bird under the wing area and there is no PP evidence that area has been locally manipulated – which leads to the conclusion that (if it is a shadow on the water – more in a moment) that ‘shadow’ is a soft shadow

3. However considering the TYPE of light hitting the head of the bird and assuming the EXIF date and time recorded is accurate (0721.03.03.2020) and (assumed) the shot was pulled somewhere south of the Murray River and that sunrise in Melbourne, 03.03.2020 was 0707hrs – then:

3a) the shadow on the water is very likely not a shadow but a Reflection

3b) at 0710hrs in March, somewhere near the Victorian seaboard and assuming there are no clouds, then EV = 09~12 would be a realistic range for the estimate of the light on the scene, a wide range to allow for the rapid change at that time of the day

3c) taking EV 10.5 as ‘read’ – then pulling the shot as per EXIF data - 1/1250s @ F/8 @ ISO2500 puts the seagull 1½ Stops, underexposed

3d) IF the shot is underexposed, then the likely cause is the misinterpretation of the (mostly water and sky) Scene by the PATTERN Metering Mode which was selected and then the lack of Exposure Compensation applied by the Photographer

Each of the above is not per se a definitive conclusion, however, in toto they do comprise a compelling case for another area of investigation of the techniques being used for BIF might require attention - understanding of the functionality of TTL Metering and appropriate and timely use of EC.

*

Continuing (Seagull over water image) -

If it is a reflection (not a shadow) on the water, then considering firstly that the SD (Subject Distance) was a relatively a long distance and secondly the Seagull is relatively close to the water, then, although, pedantically, the reflection will be a smidgen in front of the Seagull, for real world analysis we can consider both the Reflection and the Seagull to be in the same Plane.

That established, the Reflection is indeed sharper than the Seagull above it - which is exactly the complaint being interrogated.

However, if we accept that these two ARE in the same Plane we MUST conclude that there is absolutely no DoF malfeasance at play here.

Moreover, a more logical conclusion is that the Tv chosen (1/1250s) was simply fast enough to arrest any perceivable Subject Motion Blur of the momentum and direction of the Water, and NOT fast enough to arrest the Subject Motion Blur of the Seagull - which is the reason why the Seagull appears less sharp than the water.

WW