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

 

[AlainCh2]

...

... 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.

...

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

...

Ahahahaha!!!!

. 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".

...

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 do and keep doing !!!

I hope this helps.

Thanks.
That is one one the best DOF guides written for beginners.
You should do more of them and put it on a site !!!!!

It clarified to me that the DOF is related to the distance you shoot,
explaining why I do obtain a thin focus plane using macro.

I do need to use Tele instead, and find another way to blur the background

SOOC with 2 Meike ring >29mm<


I need 0.8cm Dof at least to get both the center and all the rest of the flower on the focus plane



Phone software adapts focus quite well.
You cannot really compose the lights and color as you want






Same flower same conditions







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Mid of French/Italian Alps - Hardiness Zone 8A
I Love all Carnivores, I have mostly Red Dioneas.
https://eu.zonerama.com/AlainCH2/1191151

 

[Ricosuavefoto]

Very good question...not dumb at all! I've seen lots of good answers here and I think you are getting some good info. All I will add is that you should take advantage of the best thing about digital cameras: you can take as many pictures as you want. Play with different shutter speeds and apertures to compare the difference. Also, try different doll arrangements (like lined up front to back) or take this group from the side and compare the effects. And try throwing a little more light on them...you might find you have more leeway to change settings and get different depths of field. Most of all: have fun with it.

 

[NikonMan09]

Very good question...not dumb at all! I've seen lots of good answers here and I think you are getting some good info. All I will add is that you should take advantage of the best thing about digital cameras: you can take as many pictures as you want. Play with different shutter speeds and apertures to compare the difference. Also, try different doll arrangements (like lined up front to back) or take this group from the side and compare the effects. And try throwing a little more light on them...you might find you have more leeway to change settings and get different depths of field. Most of all: have fun with it.

I would add that you should also experiment with positioning the AF box differently. Since the Nikon Z AF options give priority to the closest object, you can use that feature to advantage to get more precise focus of the desired subject. For example, positioning the AF box one row up will put the dolls' faces in the key row more in a closest object position. Being made aware of this has helped me get more in-focus shots of competitive swimmers in action with a Zfc.

 

[FingerPainter]

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".

I'm going to disagree, sort of, with that. There is a definition of "acceptably sharp". An object in a viewed photo is "acceptably sharp" if the diameter of its blur circle on the viewed photo is small enough that the viewer cannot distinguish the blur circle from a point at the selected viewing distance and print size, and given the viewer's visual acuity.

So there is a definition, but it applies to the viewing of a photo, not to the photo itself. Change the viewing distance, or the print size or who is looking at the photo, and the DoF changes. You allude to these factors below.

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.

 

[FingerPainter]

..

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.

Whether it is true depends on what your assumptions are regarding various unstated factors.

If PLShutterbug was assuming that focal length and f-number remained constant while subject distance changed and that a shot from farther distance was cropped to the same framing as the closest shot, then what he said may have been correct.

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.

Yes and every DoF calculator also takes into account the size of sensor used to make the photo. When you crop you have to use the size of the portion of the sensor that corresponds to the corp , not the size of the whole sensor.

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

https://photographylife.com/what-is-depth-of-field#camera-subject-distance

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

https://digital-photography-school.com/understanding-depth-field-beginners/

Yes as you increase subject distance, DoF increases. As you crop, DoF deccreases.

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.

DoF is all about perecived sharpness. Perceived sharpness is in the very definition of DoF.

Here is the same photo cropped and uncropped.





The depth of field is the same in each photo.

No, it is not. The blur circles in the bottom photo are only about half the size of those in the top photo, so the DoF in the bottom photo is deeper.

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.

But then you have changed the display size, and such adjustments change the DoF.

DoF is not a property of a photo. It is a property of the viewing of a 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.

And DoF is what we perceive to be acceptably sharp. And for a given viewer, this depends on display size and viewing distance.

It's not that considerations of perceptible sharpness aren't worthwhile,

in fact, they are necessary for a discussion of DoF.

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.

Yes, it is true that DoF relative to subject size in th doll photo will be much less than the DoF relative to subject size you'd get if you scaled up subject size and subject distance by the same factor. E.g. if you shot a 50mm lens at f/11 from 0.5m distance to shoot the dolls, and then used the same lens and f-number from 6 times the distance (3m) to photograph people that are 6 times the height of the dolls, then you'd get about the same framing of subjects, but the DoF in the doll photo would be about 1/5 of the height of a doll, while the DoF in the people photo would be a bit more than the height of a person. (This assumes that the photos were made on the same sensor size, printed at the same size and viewed at the same distance by the same person.)