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04-11-2016, 04:23 AM   #1
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where is the begining and end of sharpness in DOF calc, one interesting question

Well,

If I would intend to increase my sharp pics, in a manner to properly pick my aperture for the subject, I would stop down my aperture to 5,6 - 8, sometimes 11-16.

What I found out, is fact that I really don't know where is the exact depth of filed, where my subject is still sharp.

I mean, if you point your camera to the subject and nail focus on it, it would be sharp, but does that "sharp field" covers the space from that point forward or far from you and subject, or the sharpness also exist in the space in a front of you, and in a front of subject?

In other words, WHERE IS NAIL FOCUS POINT IN SHARPNESS FIELD. IN THE MIDDLE OF IT, JUST ON BEGINNING OR IN THE END OF IT.

From what I know, there is no way the nail focus point starts at the end of sharpness, because everything behind will be blurred, in smaller apertures like f8 or f16,
and it's not the case.

But the front field in a front of subject is questionable ... Is the nail focus from your camera on the beginning of sharpness, and everything in a front of is blurred,

or the nail focus is somewhere in maybe middle of that field.

WHY I'M ASK THAT?

because, when I try to catch some moving objects, and when I'm increasing my sharpness dof by stopping down aperture to f8, or f5,6, I want to know WHERE EXACTLY MY SUBJECT CAN MOVE AND STAY SHARP.

If the nail center of camera begin where sharpness begin, that means my subject can not move any closer to me, only away from me.

When I'm shooting some singers on the stage, I like to isolate them with blurred background, and because they constantly move, it's hard to guess where is your sharpness field.


I don't know am I do good explanation here, but I hope you understand... I can bring some graphics later to better visualisation

04-11-2016, 04:44 AM - 2 Likes   #2
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Have a look here, that may help

Online Depth of Field Calculator.

Typically 1/3 before and 2/3 behind the focused distance.
04-11-2016, 04:55 AM   #3
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thank you, that's pretty helpful
04-11-2016, 05:12 AM - 1 Like   #4
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QuoteQuote:
WHERE IS NAIL FOCUS POINT IN SHARPNESS FIELD. IN THE MIDDLE OF IT, JUST ON BEGINNING OR IN THE END OF IT.
The sharpest point will be exactly the distance your lens focus set (assuming no front or back focus).

Either side of this point are areas said to be of 'acceptable' sharpness based on print size, viewing distance, and even eyesight of viewer.

In using charts or calculators I would suggest taking the figure as guidelines only and perhaps consider using figures for wider aperture as a safety barrier. So say shooting f/11 use the DoF figures for f/8 or even wider.

Another calculator to look at along with Joergens DoF

04-11-2016, 05:17 AM   #5
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I just take images at various ƒ-stops and pick the best one. It's much faster than messing around. I do try and find something to focus on that's 1/3 of the way into the picture. But, it's surprising how many times the DoF setting i think would be good, is different from my preconceived idea of what it should be. Apart from picking a focus point 1/3 of the way into the area you want in focus, my only advice would be shoot with your lens wide open to ƒ 16 or 22, at least three or four exposures at different ƒ-stops. Decide what DoF you like visually on your computer.

And if you're really serious, shoot various focus points as well. Especially when shooting lenses wide open and with narrow DoF, it can be hard to predict what you want in sharp focus, and what you want to be blurred.
04-11-2016, 07:12 AM   #6
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I have found my mirrorless cameras (samsung NX20 and Lumix G1) very educational for seeing the depth of field [edit] when using them with MF lenses - the mode then is usually stop down aperture priority, so it's very WYSIWYG in terms of DoF and focus (if less so in other respects). [/edit] The advantage of the EVF is it doesn't get dimmer when you stop down (up to say f11 anyway, depending on ambient light), it auto-compensates the brightness. And the high mag focus assist means you can really zero in.
I've not found the stop down preview functions on my pentaxes so useful.

Last edited by marcusBMG; 04-11-2016 at 03:09 PM.
04-11-2016, 07:21 AM   #7
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QuoteOriginally posted by marcusBMG Quote
I have found my mirrorless cameras (samsung NX20 and Lumix G1) very educational for seeing the depth of field - the advantage of the EVF is it doesn't get dimmer when you stop down (up to say f11 anyway, depending on ambient light), it auto-compensates the brightness. And the high mag focus assist means you can really zero in.
I've not found the stop down preview functions on my pentaxes so useful.
Sounds like way to much fussing about for me. I tend to look for the no muss no fuss solution. Work quickly in the field, evaluate in front of the computer on a 27 inch 2560 x 1440 display.
04-11-2016, 07:24 AM   #8
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QuoteOriginally posted by marcusBMG Quote
I have found my mirrorless cameras (samsung NX20 and Lumix G1) very educational for seeing the depth of field - the advantage of the EVF is it doesn't get dimmer when you stop down (up to say f11 anyway, depending on ambient light), it auto-compensates the brightness. And the high mag focus assist means you can really zero in.
I've not found the stop down preview functions on my pentaxes so useful.
I was just trying to find out, is nail focus begin more in the front, exactly front, or closer to the middle of, what we called acceptable sharpness.

If I nail singer, from 3,4 m away, and he move after focusing 30 cm to me, with his body, will he be in focus if I choose for example f8 or even f11?
Or on the opposite side, If he move away 30 cm from me, after focusing.




Last edited by panonski; 04-11-2016 at 07:31 AM.
04-11-2016, 07:33 AM   #9
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QuoteOriginally posted by panonski Quote
I was just trying to find out, is nail focus begin more in the front, exactly front, or closer to the middle of, what we called acceptable sharpness.

If I nail singer, from 3,4 m away, and he move after focusing 30 cm to me, with his body, will he be in focus if I choose for example f8 or even f11?
Or on the opposite side, If he move away 30 cm from me, after focusing.

30 cm is quite a considerable movement. If you have a short telephoto lens, like 70-100mm and above, I doubt you will get sharp pictures if your subject moves that much. That is assuming you are not shorting from 100m away... The dof calculator linked above will tell you how much depth of field you'll have anyway.
04-11-2016, 07:35 AM   #10
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One Information is missing, the focal length you are using.

50 mm: 2,87 to 4.49 m 63 cm in front of the object and 99 cm behind. 1,62in total
70 mm 3,15 to 3,94 m 35cm 44 cm 0,79
100mm 3,32 to 3,70m 18cm 20cm 0,38

All numbers from the dofmaster.
04-11-2016, 07:38 AM   #11
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QuoteOriginally posted by kp0c Quote
30 cm is quite a considerable movement. If you have a short telephoto lens, like 70-100mm and above, I doubt you will get sharp pictures if your subject moves that much. That is assuming you are not shorting from 100m away... The dof calculator linked above will tell you how much depth of field you'll have anyway.

oh, sorry, 30 cm, could be 15, or 10 cm... I just want to know, where my accectable sharpness begins
04-11-2016, 08:07 AM   #12
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QuoteOriginally posted by panonski Quote
oh, sorry, 30 cm, could be 15, or 10 cm... I just want to know, where my accectable sharpness begins
In terms of depth of field calculations, the "standard" for acceptable sharpness was originally developed by a group of experts getting together and reaching a consensus about what looked sharp enough to them under specified viewing conditions. In other words, the basis for that concept is subjective. Fine by me. You have to start somewhere.

Once the experts agreed on what sharpness meant, they were able to reverse engineer the optical factors that produced the DOF required for sharpness. That's how they came up with the numbers that are used in DOF calculations.

It's up to you to decide what is acceptable sharpness for your own purposes. The best way to work that out is to get out there and systematically make pictures, evaluating results using viewing methods that reflect your intended use of your work.

If you need a good approximation of how experts see acceptable sharpness, work with a prime lens equipped with a DOF scale. Among other things, the DOF scale will tell you how much is sharp on both sides of the plane of focus.
04-11-2016, 08:35 AM   #13
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QuoteOriginally posted by John Poirier Quote
In terms of depth of field calculations, the "standard" for acceptable sharpness was originally developed by a group of experts getting together and reaching a consensus about what looked sharp enough to them under specified viewing conditions. In other words, the basis for that concept is subjective. Fine by me. You have to start somewhere.

Once the experts agreed on what sharpness meant, they were able to reverse engineer the optical factors that produced the DOF required for sharpness. That's how they came up with the numbers that are used in DOF calculations.

It's up to you to decide what is acceptable sharpness for your own purposes. The best way to work that out is to get out there and systematically make pictures, evaluating results using viewing methods that reflect your intended use of your work.

If you need a good approximation of how experts see acceptable sharpness, work with a prime lens equipped with a DOF scale. Among other things, the DOF scale will tell you how much is sharp on both sides of the plane of focus.

What he said...

All I can add is to repeat a point made a few times in other comments...Regardless of set aperture and anticipated DOF, there is only one focus point. Pixel peep, print big, or simply stand close enough to a print and "acceptable" sharpness becomes unacceptably soft. Step back, print small, or downsample to a lower resolution and all looks good.

I have used my avatar photo as an example in the past and will do so again today. Pretty deep DOF, eh? Consider the same photo at larger pixel dimensions...




Steve
04-11-2016, 08:44 AM   #14
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QuoteOriginally posted by panonski Quote
oh, sorry, 30 cm, could be 15, or 10 cm... I just want to know, where my accectable sharpness begins
I really do not think anyone can tell you unless you give specifics of camera, lens FL, focus distance and aperture and what size the image will be viewed at.

AFAIK the original calculations for DoF based on a 10"x8" print viewed at what is considered to be a normal viewing distance i.e. 1.5 -2x the length of the print diagonal. Even then you or I may not find the outermost limits of DoF to be acceptably sharp. Another factor is if you are initially viewing at 100% in your editing application you are looking at an image at a magnification of 3x that of a print from either an HP or Canon printer assuming you will print @ 300 ppi

You should really have a look and a play with the DoF charts and plug some figures in and then shoot some images using the figures or shoot first an plug figures in afterwards.
Taking the example shown below shooting with the camera and lens shown @f/5.6 you will have a total DoF of approx 1/3rd of a metre. But at f/16 you would have total DoF of approx 1 metre - problem here is that f/16 you will lose some IQ due to diffraction and you will need to decide from practical testing just where the images become unsatisfactory due to being unable to correct in post processing
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04-11-2016, 08:44 AM   #15
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QuoteOriginally posted by panonski Quote
is nail focus begin more in the front, exactly front, or closer to the middle of, what we called acceptable sharpness.
Roughly 1/3 of the perceived depth of field is in front of the focus point. But that ratio changes depending on aperture and distance to the focus point. Perceived sharpness is dependant on other factors as well, such as contrast and composition. Our brains do mental sharpening based on visual clues triggering our memory and we tend to mentally extend perceived sharpness towards the background, not towards the foreground. It seems to me that if you get one recognizable object in the foreground clearly focused, our brain fills in more out of focus areas than if you focus on something we can't tell if it is in focus or not because we don't know what it looks like in real life, or if the foreground is noticeably out of focus, we tend to see the in focus parts in the background as blurry.
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