Super Noob Question regarding focus.

[Coffee_Girl]

I feel so dumb asking this; My issue is i don't understand auto focus modes, I have a red box on my screen and everything outside of that red box is blurry. ...but what if the subjects are 10 people and the box isnt wide enough to fit them all in there? Do i have to walk further away...would the quality of my photo decrease?

I am practicing using dolls as subjects with a 50 mm lens...i sit about 3 feet away and the dolls not in that red box are blurry...i dont understand how to get rid of this box. I am also using an Aperture of 10





Notice the doll in the back is very blurry



I own a Nikon Z6II with an FTZii adapter 50mm lens AFS Nikkor 1.4G

 

[J2daV]

Try this Ricci video about autofocus modes and how they work.

it might be getting less sharp at f/10 from diffraction

https://photographylife.com/what-is-diffraction-in-photography/amp


if the lens always seems to have part that is out of focus, you could have a lens that is decentered. Meaning one of the lenses inside has moved and isn’t straight with the others.

 

[Laqup]

This is only partially an issue of "auto focus". The bigger part is understanding photographic basics first.

This is a fullframe sensor. You are using a lens approaching portrait focal lengths at a very short distance. This is not the way to get everything in focus with such a big sensor. The strong point of full frame cameras is "separation capability", which means sharp subject, blurry background. You are trying to achieve the opposite.

If you wanted to get a lot of things in focus at those short distances with a full frame camera you need a much wider lens (e.g. 24 or 28mm @ f/10). 24mm might already be too wide, which will lead to distortion effects on the image borders. Certainly not optimal for portraits.

With actual humans your method will work somewhat better, as you will have to maintain a much higher distance from your subjects. This will automatically lead to an increased field of depth = more in focus. Going very close to the subject is a typical trick to get best possible separation. This way even smartphones provide some out of focus areas without computational tricks.

I will not go into detail how to change focus mode, as this is part of the manual or can be understood by watching one of those very basic "AF modes of the Z6 explained" youtube videos.

 

[Vince P]

I feel so dumb asking this; My issue is i don't understand auto focus modes, I have a red box on my screen and everything outside of that red box is blurry. ...but what if the subjects are 10 people and the box isnt wide enough to fit them all in there? Do i have to walk further away...would the quality of my photo decrease?
I am practicing using dolls as subjects with a 50 mm lens...i sit about 3 feet away and the dolls not in that red box are blurry...i dont understand how to get rid of this box. I am also using an Aperture of 10



Notice the doll in the back is very blurry

I own a Nikon Z6II with an FTZii adapter 50mm lens AFS Nikkor 1.4G

It's never dumb to ask. If what you are focusing on is in focus then that's a good place to start. Everything that is the same distance away will also be focus.

There are some topics you may want to do some research on, but for this issue, first should be depth of field, which is related to aperture.

The 50mm 1.4 lens has a wide maximum aperture of 1.4 which means that when you shoot at 1.4 there is a large opening which let's lot's of light in so you can shoot in darker conditions and use higher shutter speeds. However it also means that objects closer and further away than where you are focusing will be blurry as you notice. Sometimes this is something you may want of they are distracting or you want to emphasis a particular subject. This distance in focus also varies with how far you are from the subject and focal length. So even at F10 )As you have found) at close distances (Or magnification) the depth of field is still not that deep.

This is a great lens to experiment with depth of field and how aperture affects it. As you close down the aperture (So making the F numbers higher) the more of the image will be in focus. This will mean that your shutter speed will need to slow down or you will need to raise your ISO (Which means the image won't look quite as good in terms of noise and colours but that's something to worry about once you get the hang of it. The easiest way to try this, whilst you are experimenting is to use Aperture priority "A" on the dial and set the ISO, to automatic, and then see how much is in focus when all you change is the aperture. You will see how the increase in ISO affects things.

Enjoy your new camera, it's a steep learning curve but one of the best things is that you never stop learning or using what you will learn in the first few days.

 

[Bob A L]

Do more study on your manual. Not necessarily everything in the red box will be sharp. It depends on what you told the camera to concentrate on. If you want one specific doll to be in focus, you need to use manual focus with a small focus spot on the desired doll.

And as others have said, the depth of field will be much deeper at 10 feet than it is at 3 feet, meaning more things can be in focus.

Study your manual, read lots of books and study up on depth of field.

 

[PLShutterbug]

Hey, thanks for giving me a good reason for finishing something I started over a week ago! This is cool. Someone who wants to learn.

I feel so dumb asking this; My issue is i don't understand auto focus modes, I have a red box on my screen and everything outside of that red box is blurry.

It's not that everything outside the red box is blurry. Note that the doll with the necklace on the left, and the one one in the purple dress on the right, are about as sharp as the two who are inside the box. The doll in the back, whose face coincidentally is outside the box, is not sharp.

What's happening is what another poster referred to: it's where the principal point of focus is, and the depth of field in the image based on your aperture settings.

...but what if the subjects are 10 people and the box isnt wide enough to fit them all in there? Do i have to walk further away...would the quality of my photo decrease?

I'll explain and illustrate below.

I am practicing using dolls as subjects with a 50 mm lens...

Good idea. You'll learn a lot about focus and depth of field this way.

i sit about 3 feet away and the dolls not in that red box are blurry...

I'll explain and illustrate below.

i dont understand how to get rid of this box.

Separate discussion, but what do you mean by "how to get rid of" the box? As you are taking the photo? When you view the photo you just took on the camera's monitor (that's what Nikon calls the LCD display on the back of the camera)? When you are viewing the picture after transferring it to your computer? Let us know exactly what you mean by "get rid of this box."

The box there shows you the part of the image you are about to take where the camera will try to autofocus within. Generally, the camera looks for the point closest to it that is inside the box. In this case, it is the probably the right hand of the second-to-right doll.

Play with all of the different autofocus modes and settings, carefully read the camera's manual, and come back here and ask questions. That's the best way to learn. You use those different AF settings (or manual focus) depending on what you are shooting.

I am also using an Aperture of 10

If you want to be a Real Photographer Nerd, you'll write "I'm shooting at f/10." The word "shooting" makes you sound more deadly. When you speak that last bit, it's just "F ten" - you don't say "F-hyphen-ten," but just "eff ten." But I digress.

Notice the doll in the back is very blurry

That's depth of field (or lack of it) biting you in the a**. See below ...

I own a Nikon Z6II with an FTZii adapter 50mm lens AFS Nikkor 1.4G

Nice setup.

Last weekend someone else asked about depth of field in relation to focus stacks (we won't get into that here) so I created the ruler you see in the photos below. What it does is show you how much of your image is in focus when you take a photo. The reason I did it is to illustrate a concept called "depth of field." You'll also see it referred to as DOF. Simply put, DOF is the amount of a photograph closer to the camera and further away from the camera than the "principal point of focus" that is "acceptably sharp."

The principal point of focus is a plane (not a point) at the distance at which the camera is focused. There is only one principal point of focus in an image. It extends left-to-right, and up-and-down, through the entire image. (Purists will argue about field curvature but we will ignore that for the purposes of this discussion.) It is parallel to the camera's focal plane.

Here is an illustration showing how DOF works in relation to these other terms.


Depth of field is a function of the diameter of the aperture of your lens. Lenses can vary that aperture. The wider the aperture, the smaller the depth of field. The narrower the aperture, the greater the depth of field.


Shot at f/3.

(For those of you who might be curious, that's a Kodak Polycontrast 8/10 100-sheet box from the early 1970s. Double weight. There is no bar code on the box, so it is from earlier than about 1975.)

Here, I've focused the lens at the 4" mark, so that horizontal line is razor sharp. (Note: this is not a 4" focus distance. It is just 4" on the scale you see. The actual focus distance from focal plane to the 4" mark was 31-3/4".) I used AF-S (single-shot focus), in pinpoint mode, and placed the pinpoint at the intersection of the 4" mark and the vertical line.

The batteries to the right are placed in the same plane as the 3", 4", 5", 6", and 7" marks on the ruler. The ruler was designed so that at the angle I'm shooting it, those marks actually represent exact distances in real life.

Note that the second battery, exactly lined up at the 4" mark, is also in focus. Again, the principal point of focus represents a plane that is parallel to your camera's sensor, not a point.

This first shot was taken at the widest aperture of my Nikkor Z 105mm MC lens. At this focus distance, that is f/3. At that aperture, depth of field is from about 3.9" to 4.2".

The focus box in this case covered the intersection of the 4" line and the vertical line and no more. The focus box was about 1/32" square in this image. So the focus box only represents where the AF system will look for focus. It doesn't represent the part of the image that will be in focus. The camera will generally focus on the closest object within the focus box.

Here is another shot, at a smaller aperture (larger f-number). I'm still focusing on the 4" mark.


Shot at f/5.6

This was shot approximately two f-stops "stopped down" compared to the first image, at f/5.6. This illustrates that as you narrow the aperture - as you increase the f-number - your depth of field increases. You can see that the words on the first and third batteries are easier to read even though they are still somewhat blurry. Depth of field has increased to about 3.8" to 4.3"

Here is a third shot, stopped down two more stops to f/11.


f/11.

Here, DOF is from 3.5" to 4.6". Note that DOF is subjective: only you can say whether any point in one of your images is "acceptably sharp." There are Official Tables (yes, I'm using capitals for emphasis), but "acceptably sharp" to one person may be horribly out of focus to someone else.

Note here also that the word "Kirkland" in the third battery, at 5", is sharper than the same word in the first battery. While DOF is measured as a distance, such as "one-half inch at f/5.6 with a 105mm lens at 32 inches" or " from 4 feet to infinity at f/16 with a 14mm lens", you will always see more "acceptably sharp" points further from the principal point of focus (PPOF) than closer to the camera. The general rule is that 1/3 of DOF is in front of the PPOF and 2/3 is behind it (though people will argue that ...). This image does illustrate that a point the same distance closer to the camera will be less sharp compared with a point further from the PPOF. Physics.

Here is a fourth image, this one stopped down two stops to f/22.


f/22

Now batteries 1, 2, and 3 are reasonably sharp. DOF is now from about 2.6" to 5.5".

Note also that as the aperture is stopped down, less light is let into the lens. To get the same exposure you must lengthen the shutter speed.

Finally, here is a shot at the lens's minimum aperture, f/36.


f/36.

At this aperture, all but the 5th battery are "acceptably sharp" and even that one is close. DOF is now from 1.8" to about 6.8".

Someone here mentioned diffraction. As you stop a lens down, to smaller and smaller apertures, at some point the lens actually becomes less sharp overall while more the the image becomes "acceptably sharp." This is due to a physics phenomena called diffraction. If you are concerned about the absolute sharpest image at the PPOF, every lens will have an aperture that provides that. For this lens it looks like the photo at f/11 is the sharpest. But unless you are really picky, the second battery in every image is "acceptably sharp" and even at f/36 every battery in the image is "acceptably sharp" except for #5 (at 7").

Note also that I refocused all of these images for each shot. Focus may have missed by a tiny amount between images. The "right" way to do this test would be to set the camera to manual focus, magnify the image in the viewfinder, focus critically, and then leave it for all five shots. I'm too lazy for that.

I shot all these images with a Z8 and Nikkor Z 105mm MC f/2.8 lens, from a tripod, using a two-second delay after I pressed the shutter to eliminate any shake from my having pressed the shutter, and at the camera's base ISO of 64. Here are the exposure settings:

1: f/3, 1/25s

2: f/5.6, 1/8s

3: f/11, 1/2s

4: f/22, 2 seconds

5: f/36, 5 seconds

So after all this, I hope it's obvious that to get all those dolls sharp you have to use a small aperture, probably f/22.

As you get further from a subject, depth of field increases at the same aperture. Since I was very close the DOF is measured in fractions of an inch at a wide aperture. If I was fifty feet away it would be measured in many feet.

The angle of view also affects depth of field, at the same distance. A 24mm lens at 5' focus distance will have a wider DOF at f/4 than a 50mm lens at the same distance and f-stop.

All of this takes practice and time. You'll get there, just keep practicing.

I hope this helps.

 

[SCoombs]

In a photo (or a video) everything that is a certain distance away from the camera will be in focus. When you adjust the focus, the distance at which things are in focus changes.

For instance, say you us the autofocus to focus on a rock that is 10 feet away. Now as you move the camera around and point it at different things, anything else that is also 10 feet away will be in focus, too. Things that are closer or further than 10 feet will not be in focus.

Well, actually, it's slightly more interesting than that because the reality is that there is a range of distance for what is in focus. It wouldn't really just be things that are exactly 10 feet away that were in focus in the above example, but things that are within a certain range approximately centered on 10 feet. Depending on a few different factors that range might be, say, 6 inches, so that everything you point the camera at that is 10 feet is away, or 9 feet 9 inches away, or 10 feet 3 inches away, or anything in between is in focus. Or, the range might be 2 feet, so that after you focus on that rock you can then get in focus anything else that is between 9 and 11 feet away. This is called depth of field.

There are several things that impact how wide the range is, but for now the simplest one to understand is that having a smaller aperture number (the f number) will make the range of focus smaller. If you have your camera set at f/4.5 you will have a more narrow range of what's in focus than if it's f/8.

So what is going on with your dolls? First understand that the red focus box isn't making everything inside of it be in focus. Rather, it's telling the camera what object to try to focus on. Here is a photo I was working on recently:



Notice that the chipmunk's face is in focus. When taking this picture, I actually had the focus box on his face. This told the camera to try to focus on his face (I was going for the eye). Notice that his nose is also in focus, as is the stick he is standing on. Even though the box was only on his eye, the nose and stick are in focus because they are about the same distance away as his eye. Meanwhile, other parts of the photo, like the chipmunk's feet and body and tail and the sticks behind him are not in focus. It is possible that some of these things were also in the red box, but they are not in focus. This is because the box doesn't make things be in focus: it just tells the camera it should focus on something inside that box. Depending on the camera and settings, it might choose whatever the closest thing is inside the box, or it might try to find a facial feature like an eye to focus on inside the box. Either way, it can only pick one distance inside that box to focus on.

So in this case, probably the box was covering his face and some of the body and sticks, but not the big stick he's standing on. The camera picked the eye to focus on and so the eye is in focus as well as things about the same distance away. This includes things inside the red box that are about the same distance away like the nose, as well as things not in the box that are nevertheless about the same distance away like the large stick. It means things not the same distance away, like the body and other sticks in the background, are not in focus even if they were in the red box.

Back to the dolls, the reason the two dolls in the red box are in focus is that they are about the same distance away. Other dolls outside the box just happen to also be behind these two, so they are outside the range of focus. Most likely, the camera either interpreted the face of the doll 2nd from the right as a person and focused on that, or else it saw the hair or chest of that doll as the closest thing inside the box and focused there. This makes the darker doll also be in focus since it's a similar distance away and, actually, the rightmost doll, though not in the box, is nice and sharp and in focus since it's also not much further away than the one in the box. The two in the back are not in focus as they're further away from the focus point (the blonde doll) and outside of the depth of field of this shot.

What if you had real people and wanted to get them all in focus? Three thoughts. First, you can try to have them stand so they're roughly the same distance away from the camera. With smaller groups this is pretty normal to do anyways since people often line folks up for group shots.

Second, if you need to have them in two rows or otherwise don't want them lined up, you can increase the depth of field by using a larger f number. For instance, if you stand about 6 feet away from your subjects with the camera and lens you report and use it's largest f number of 1.4, your depth of field is about 5 inches - but if you chance it to f/8, the depth of field is about 30 inches! There are other reasons for changing the f/ number, so keep in mind I'm just giving some examples. You may want a smaller depth of field or need to use a smaller f number since in darker light the smaller f numbers are better.

Third, you could stand further away from the subjects - something you'd likely be doing anyways with people vs. dolls. For instance, if we took that f/1.4 at 6 feet away which gives 5 inches of depth of field, if you moved back to 12 feet away the depth of field would be about 21 inches, which is probably enough to get two rows of people. This is a very rough estimate, but say you wanted to photograph 8 people in two rows of four. Let's go with 8 feet across as the amount of space you need. If I'm not mistaken, that would require you to stand about 11.5 feet away with that lens, putting your depth of field in that 20 inch range or so - and that's at the very small f number of 1.4. It would not be uncommon to use f/2.8 or f/4 or even f/5.6 for a group shot like that. Even at 2.8, a very common portrait aperture, you're getting around 3 feet of in focus area to work with. At f/5.6 it's over 6 feet if you are standing the 12 feet away we talked about.

My point isn't to confuse you with all these numbers and you don't need to constantly remember all of this or use a calculator (like this one https://www.photopills.com/calculators/dof) before you take every photo. Rather, my point was that if you're taking photos of real live human beings then you're going to be taking care of the "how far am I from the subject" stuff anyways just by the fact that you're photographing people, and so if you do something as simple as keep that f at 2.8 or 4 or so you shouldn't really have any problems with people being out of focus.

 

[SoCalAngler]

Nice summary I think.

One thing that may be missing (unless I missed it) is that there is no absolute definition of what "acceptably sharp" means. Or to put it differently, there is no specification that defines "acceptably sharp".

It is rather subjective and can depend on individual perception and preferences and aside from camera/lens settings, for each individual viewing an image, can depend on output size (e.g print size, size on screen, etc) and viewing distance.

For example, I have many images that I have saved captured with a 24mp full frame or APS-C sensors that do not look acceptably sharp to me when viewed at 100% on my 27" iMac, but when printed at 8" x 12" are acceptably sharp to me as well as others who have seen them as close as 18" away or even closer. I have some images that look fuzzy at 8x12 but fine in a 4x6 print.

I had a 20"x30" poster print made from a Nikon D40 image (6MP sensor) that was considered acceptably sharp for its intended purpose by the users of the print, which was to be placed about 8' above ground in a booth at a trade show where the nearest viewers were at least 12' away.

I see prints all time in folks homes that look great to them don't meet my standards for what I would print an display. On the other had I have prints on my wall that some viewers felt were not "acceptably sharp" by their preferences but I was perfectly satisfied with.

What I am getting at is that an image may appear a bit soft or out of focus, whether it be due to a lens issue, missed focus, diffraction, atmospheric conditions,maybe a bit of motion blur, or some other reason, may still be quite usable ("acceptably sharp" at a desired output size and viewing distance.

That said (written), I still want to understand all of the camera/lens/light parameters that affect the captured image data so that I can get the best data to work with. However if I don't get a result that is perfect when viewed at 100% on a computer screen, it still my be useful for a specific need - and examining the image may help me with improving my technique.

 

[PLShutterbug]

Nice summary I think.

Thanks.

One thing that may be missing (unless I missed it) is that there is no absolute definition of what "acceptably sharp" means. Or to put it differently, there is no specification that defines "acceptably sharp".

It is rather subjective and can depend on individual perception and preferences and aside from camera/lens settings, for each individual viewing an image, can depend on output size (e.g print size, size on screen, etc) and viewing distance.

I mentioned that in my screed, but not in great detail.

 

[SCoombs]

Nice summary I think.

Thanks.

One thing that may be missing (unless I missed it) is that there is no absolute definition of what "acceptably sharp" means. Or to put it differently, there is no specification that defines "acceptably sharp".

It is rather subjective and can depend on individual perception and preferences and aside from camera/lens settings, for each individual viewing an image, can depend on output size (e.g print size, size on screen, etc) and viewing distance.

I mentioned that in my screed, but not in great detail.

I think that all of this information about what "sharp" means is true, but I also think it's pretty far outside the scope of what the OP is trying to understand and is more likely to confuse someone trying to understand basic ideas about how autofocus works than to help them.

 

[Coffee_Girl]

Thank you so much, your answer really allowed me to understand things better especially with the squirrel as an example. you have no idea what a difference you have made in my photography journey!!

 

[Coffee_Girl]

This is an AMAZING write up, with educational photos, thank you! I was shocked to learn that your aperture could reach up into the twenties...mine stops at f16 ...is this normal or is it because of my lens or perhaps my camera wont get any narrower? ( Or maybe because i am using an adapter aka an older lens?)

 

[allanimal]

I was shocked to learn that your aperture could reach up into the twenties...mine stops at f16 ...is this normal or is it because of my lens or perhaps my camera wont get any narrower? ( Or maybe because i am using an adapter aka an older lens?)

The aperture range depends on the lens, not the camera.

 

[Coffee_Girl]

I keep reading and rereading your post and suddenly it became clear to me why so many youtube videos tell you to "find an anchor in the middle of the group" when taking group photos (like graduation photos where there are rows of people behind and in front).

They mean that you should find the most center person and hope that the camera's DOF can capture everyone in front and in the back (with the photographer standing a long distance away and with i assume a narrow f-stop)

 

[PLShutterbug]

This is an AMAZING write up, with educational photos, thank you! I was shocked to learn that your aperture could reach up into the twenties...mine stops at f16 ...is this normal or is it because of my lens or perhaps my camera wont get any narrower? ( Or maybe because i am using an adapter aka an older lens?)

Thank you!

That Nikkor only stops down to f/16. Minimum aperture is a function of the lens design, not the camera. The FTZ doesn’t have anything to do with it, either. This is purely the lens.

 

[PLShutterbug]

I keep reading and rereading your post and suddenly it became clear to me why so many youtube videos tell you to "find an anchor in the middle of the group" when taking group photos (like graduation photos where there are rows of people behind and in front).

They mean that you should find the most center person and hope that the camera's DOF can capture everyone in front and in the back (with the photographer standing a long distance away and with i assume a narrow f-stop)

Standing a long ways away only makes the image smaller. If you do that and then crop, you end up with the DOF of a larger aperture from a closer distance.

For groups with several rows of people you will generally be standing 10-15 feet away to get everyone in the frame. At that distance you can use f/8 or f/11 and you will have good DOF for the group.

Focus about 1/3 of the way from front to back, as I said in my earlier post. That gives you the best overall DOF for the aperture you selected.

You can and should also bracket your f-stops.

 

[SCoombs]

I keep reading and rereading your post and suddenly it became clear to me why so many youtube videos tell you to "find an anchor in the middle of the group" when taking group photos (like graduation photos where there are rows of people behind and in front).

They mean that you should find the most center person and hope that the camera's DOF can capture everyone in front and in the back (with the photographer standing a long distance away and with i assume a narrow f-stop)

Standing a long ways away only makes the image smaller. If you do that and then crop, you end up with the DOF of a larger aperture from a closer distance.

I'm fairly certain this is not true. First, every depth of field calculator out there takes as an input the distance to the subject and shows an increased depth of field with increased distance, and this is because the mathematical formulas at play do include focal distance as a factor.

Second, many, many articles comment on the impact of distance to subject on depth of field. Here are a few:

Understanding Depth of Field - A Beginner's Guide

Depth of field (DoF) is one of the most important concepts in photography. Understanding what DoF is and what affects it is critical for every photographer.

photographylife.com

bhphotovideo.com/explora/photography/tips-and-solutions/depth-of-field-part-i-the-basics

Depth of Field: The Essential Guide (+ Tips)

Take control of your photography with depth of field. Capture stunning images with the perfect balance of sharpness and blur.

digital-photography-school.com

I think you may be conflating the idea of perceptible sharpness - that as a subject becomes smaller to our field of vision it can appear sharper - with depth of field.



Here is the same photo cropped and uncropped.









The depth of field is the same in each photo. We can see this if we look at the larger photo and zoom in so that the goslings are the same size as in the cropped photo. However, the goslings appear to be more in focus in the uncropped version because they are small enough that we it's more difficult for us to perceive the difference in focus between them.



It's not that considerations of perceptible sharpness aren't worthwhile, but for the OP's purposes here what matters is that the mere fact that it will be necessary to stand further away from a group of people versus a group of dolls means that the very shallow depth of field making to of the dolls appear out of focus won't be a concern in the same way for a photo of a group of people.

 

[Coffee_Girl]

I was wondering about what difference it would be between 11" dolls and actual humans, It feels as though shooting humans in groups would be much easier than dolls. But the advice above about shooting in aperture mode and just testing out different apertures is something i have been doing

 

[Leonard Shepherd]

Notice the doll in the back is very blurry

I own a Nikon Z6II with an FTZii adapter 50mm lens AFS Nikkor 1.4G

If you are really new to photography try holding a finger up and focussing on your finger and something like a picture behind your finger on a wall - at the same time.

You cannot!

The reason is that the human eye "sees" a very narrow zone of sharpness.

To get round the narrow zone of sharpness the human eye rapidly records a series of images at different distances, sends them to the brain - and the brain processes the sharp bits from each image to create an illusion of front to back sharpness.

A camera can record a very narrow zone of sharpness at a wide aperture such as f1.4 - and blur the background - if you want viewers to concentrate on detail at a specific distance.

If you want the background sharp as well you can use an aperture around f11 or f16.

I speculate you took the photo at f1.4 - and f11 or f16 would have given you the effect you wanted.

When something is in focus, such as the front row of dolls, everything on the same line parallel to the camera back is usually also in focus.

Back to the eye recording images at different distances, it takes the brain time to process the information.

I cannot find an authoritative source. The time seems to be reported as between 1/60 and 1/125 of a second.

You can "blur" moving water or moving traffic with the camera stationary and a shutter speed of about a second, or "stop" movement much too fast for the eye to see with a shutter speed faster than about 1/1000 or electronic flash.

Once you have mastered how to control camera effects, images very different to what the eye/brain normally perceive can be taken.

Digressing somewhat, advanced Mobile phones can take several images without you realising to produce either a wider zone off sharpness or the exact moment of a smile. Olympus and some recent Canon have a camera setting to do something similar for the zone of sharpness, but not the smile.

--
Leonard Shepherd
In lots of ways good photography is similar to learning to play a piano - it takes practice to develop skill in either activity.

 

[Laqup]

Notice the doll in the back is very blurry

I own a Nikon Z6II with an FTZii adapter 50mm lens AFS Nikkor 1.4G

To get round the narrow zone of sharpness the human eye rapidly records a series of images at different distances, sends them to the brain - and the brain processes the sharp bits from each image to create an illusion of front to back sharpness.

You must have amazing eyes or maybe I missed a firmware upgrade, but my eyes/brain do not seem capable of focus stacking.

If I focus on a finger close to my face everything else stays blurry. #sad_story.