Hyperfocal distance

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Does anyone know the Hyperfocal distance of the Yi's lens?

Id like to know at what distance i should hang up the moire pattern .
 
cant help directly as i dont have my yi yet but maybe point you in the right direction:
http://www.dofmaster.com/dofjs.html

circle of confusion for a sensor that size should be 0.004, f-stop is 2.8, distance does not matter.
the focal length should be contained in the exif - thats whats missing :)
 
Am I doing this correctly?

CoC: 0.004 mm
Focal Length: 3 mm (2.75 mm +/- 5%)
F-stop: 2.8

Hyperfocal distance 2.62 ft

Subject Distance: 2 ft ---> Near/Far Limit: 1.13 ft/8.42 ft
Subject Distance: 3 ft ---> Near/Far Limit: 1.4 ft/infinity
 
Yes thats correct. But my CoC value was rounded to much.
CoC of a multi color digital sensor is two times the pixel size (or unit size):
1.12 μm × 2 = 0.0024 mm
f-Stop: 2.8
focal length: 2.75 mm

Resulting in:
Hyperfocal distance 111.7 cm
Circle of confusion 0.0024 mm

Depth of field extends from 56 cm (half of the hyperfocal distance) to infinity. Any object in front of 56 cm is not sharp, any object behind 56 cm to infinity will be sharp.

So essentially you will need to put something 112 cm in front of you and focus the camera on this point to get "infinity sharpness".

My understanding is that correcting the lens should be done while focusing on something 112 cm in front of you for maximum deph of field BUT this is not necessarily the best focus point as 56 cm in front of the camera will be blurry.
 
Last edited:
Yes thats correct. But my CoC value was rounded to much.
CoC of a multi color digital sensor is two times the pixel size (or unit size):
1.12 μm × 2 = 0.0024 mm
f-Stop: 2.8
focal length: 2.75 mm

Resulting in:
Hyperfocal distance 111.7 cm
Circle of confusion 0.0024 mm

Depth of field extends from 56 cm (half of the hyperfocal distance) to infinity. Any object in front of 56 cm is not sharp, any object behind 56 cm to infinity will be sharp.

So essentially you will need to put something 112 cm in front of you and focus the camera on this point to get "infinity sharpness".

My understanding is that correcting the lens should be done while focusing on something 112 cm in front of you for maximum deph of field BUT this is not necessarily the best focus point as 56 cm in front of the camera will be blurry.
Normally it's best to focus it a little further away than that, or focus it while the camera is hot, otherwise infinity may go out of focus when the camera gets hot in midday sunshine.
 
I will test it out after getting my Micro-HDMI cable.
 
So I should focus my camera @ roughly 120cm (+- 4 feet)?
 
yes - did mine a week ago with hdmi on a 42" screen and snapping pictures on 3 lens positions
(marked the position with a white pencil, a grey one will probably do the trick too).

as expected i now got a slight blur on closeups.
i will use the camera mostly for motorcycle stuff on my helmet so i doesnt matter.

very happy with the results and the quality of this great 60 € camera.

edit::..
btw. i think the camera should have a normal operating temperature.
not to hot (continuous hdmi out will get the camera really warm) and not ice cold.
just let it record for a few minutes.
 
So I should focus my camera @ roughly 120cm (+- 4 feet)?
Hello
I'm a bit confused about hyperfocal value for the Yi.
Some say it is 112 cm, others 120 cm.

I found 43 cm but i'm not sure cercle of confusion value I used was right.

Sensor diagonal: 7.77mm (Sony Exmor R/IMX206)
Focal length: 2.73mm
F-stop: 2.8
Pixel size: 0.00134mm

CoC = (1 / ViewingResolution) / (250 / ImageDiagonal)
CoC=(1/5)/(250*7.77)=0.006216 mm
CoC cannot be smaller than 2 pixels (0.00268mm) on digital sensors so no problem here with value above.

Hyperfocal=(Focal²/(F-stop*CoC))+Focal
Hyperfocal=(2.73²/(2.8*0.006216))+2.73=43cm

So If focused at 43 cm, image should be sharp between 21.5 cm and infinite.

Is this right?


Links I used:
 
Is this right?
no. the general concept of hyperfocal distance:
its the nearest focus point in front your camera AFTER everything will be sharp. so every point after 112 cm is fine too.

112 cm or 120 cm or even 150 cm doesnt matter.
nigel and bosiwow set it at 120 cm so they can be sure to have the infinity sharpness
because even than you simply will not be able to focus exactly at 120 cm.
you cant focus your camera within one centimeter via hdmi you or even with pictures.
humanly not possible ;-)
 
Focal is not 3 mm, CoC is not 0.006 mm.
these values are extremely imported, you cant just round them with a sensor that small.
CoC is two times the unit size of a digital sensor - not more, not less. dont use formulas for film and printing images.

but you two go and focus your camera on a distance under 1 m while every tutorial says to focus it on
some point far in the room :rolleyes:
 
Focal is not 3 mm, CoC is not 0.006 mm.
these values are extremely imported, you cant just round them with a sensor that small.
CoC is two times the unit size of a digital sensor - not more, not less. dont use formulas for film and printing images.

but you two go and focus your camera on a distance under 1 m while every tutorial says to focus it on
some point far in the room :rolleyes:
Can you provide a link/source where it is stated that CoC is 2 times the pixel size for digital sensor?
I only found links saying that CoC cannot be smaller than 2 times pixel size.

Let's take a full frame like 5d mark II
CoC is 0.03mm as stated here
2 * pixel size is 0.0128mm

I may be wrong and if it's the case I'd like to understand why.
 
Focal is 2.7mm, but DoFmaster does not allow to enter less than 3mm
And for small-sensors, a CoC value of about 0.006 is appropriate.
Explain please if I am wrong...

Focal is not 3 mm, CoC is not 0.006 mm.
these values are extremely imported, you cant just round them with a sensor that small.
CoC is two times the unit size of a digital sensor - not more, not less. dont use formulas for film and printing images.

but you two go and focus your camera on a distance under 1 m while every tutorial says to focus it on
some point far in the room :rolleyes:
 
If you want to print your images via offset print with 300 dpi 0,006 is totaly fine.
but i am guessing you dont want to print your videos ;-) these values are based on the 35 mm film, crop factor and printing resolution.
but you are not printing your videos, you dont need to scale it for 300 dpi. 1 pixel in your video is 1 pixel on your monitor.
none of these calculation is actually with the sensor size and unit density.

lets break this down to the basics:
we dont want blur. tuning the camera to hyperfocal distance means max. sharpness.
as your coc gets bigger you will have more blur, smaller coc less blur.
let me quote dofmaster here:
"Note that the circle of confusion is subjective. Thus, some people use 0.025 mm as the circle of confusion for 35mm format, while others will use 0.030 mm.
There isn't a "correct" value."

But we know that the coc cant be smaller than 2 times the unit size of the sensor.
this is something you cant define for film (subjective per person). but for digital sensors we can say that the smalles possible coc is 2*unit size.

for the hyperfocal distance and ONLY for this distance the smalles possible coc value is the best choice.
0.006 or even 0.009 is fine (and your personal choice) but it is not the hyperfocal distance you will get.
you will get a blurry background with those values but your image might look good as the foreground improves.

if you really want to see it for yourself just focus the lens on a moire pattern or focus tester
(i really like http://www.traumflieger.de/desktop/fokusdetektor/fokusdetektor.php) with both distances (55 cm and 120 cm).
take a picture outside and post the same 100% crop here. i am not going to unglue with camera just to prove a point :p because my focus is really ****ing fantastic.
 
here is the default value export from YiCam jpg exif
Code:
Aperture                        : 2.8
Scale Factor To 35 mm Equivalent: 8.8
Circle Of Confusion             : 0.003 mm
Field Of View                   : 73.7 deg
Focal Length                    : 2.7 mm (35 mm equivalent: 24.0 mm)
Hyperfocal Distance             : 0.78 m
 
here is the default value export from YiCam jpg exif
Code:
Aperture                        : 2.8
Scale Factor To 35 mm Equivalent: 8.8
Circle Of Confusion             : 0.003 mm
Field Of View                   : 73.7 deg
Focal Length                    : 2.7 mm (35 mm equivalent: 24.0 mm)
Hyperfocal Distance             : 0.78 m

luckylz , is that info 100 % correct, i mean the hyperfocal distance ?
 
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