For advice, about hyperfocal distance.

Hyperfocal distance velocity algorithm (focal length estimation algorithm)

Hyperfocal distance's original calculation formula is:

Hyperfocal distance = lens focal length+(the square of lens focal length divided by the product of c and f). F is the aperture coefficient and c is the diameter of the diffusion circle. The early textbooks were all set to 0.05, that is, 1/20 mm, and the Jing Shenbiao on the old lens was drawn according to 1/20mm. Do not believe you can do the calculation according to your lens. Now they are all set to 1/30mm, and some are set to 1/40 mm. I think it has something to do with the photo size.

Because the focal length of the lens is much smaller than (the square of the focal length of the lens divided by the product of c and f), the general formula is written as:

Hyperfocal distance = the square of the focal length of the lens divided by the product of c and f.

In practice, the formula is improved as follows:

Hyperfocal distance = (square of lens focal length /c)/F Let (square of lens focal length /c)=K, temporarily called hyperfocal distance coefficient.

Hyperfocal distance =K/F

Then calculate the hyperfocal distance coefficient k when the common focal lengths are 16 mm, 20 mm, 24 mm, 28 mm, 35 mm and 50 mm, and the diffusion circle diameters are 1/20, 1/30 and 1/40 respectively. The results are as follows:

(k) (focal length) 16 mm 20 mm 24 mm 28 mm 35 mm 50 mm

The diameter of the dispersion circle is1/4010.241623.0431.4049100.

1/30 7.68 12 17.28 23.5 36.75 75

1/20 5. 12 8 1 1.52 15.68 24.5 50

For the convenience of memory and calculation, k is simplified to a lower value.

(focal length)16mm 20mm 24mm 28mm 35mm 50mm

K Jane 81116 22 32 64

What we are seeing now is a set of very familiar numbers, that is, the aperture coefficient (the first order number), and k is simply equal to the value of k when the diameter of the dispersion circle is 1/30.

Now it's easy to make hyperfocal distance with your mouth as long as you remember the K-simple value corresponding to the focal length.

For example, the hyperfocal distance of a 28mm lens at f/4 is 22/4=5.5m, the hyperfocal distance of f/ 16 is = 1.4m, and the hyperfocal distance of f/22 is 22/22 =1m.

For example, the hyperfocal distance of a 20mm lens at f/2 is1/2 = 5.5m, hyperfocal distance at f/116 is 0.7m, and hyperfocal distance at f/22 is 18.

Because both numerator and denominator are numerical values of aperture coefficient, the more calculation, the easier it is, because the numbers 1, 2, 0.5, 1.4 can never be found.

Some precautions:

1) Because the distance scale on the lens (distance scale, not Jing Shenbiao) is discontinuous, even if the exact value of hyperfocal distance is calculated, it is not accurate, so in practice (k Jane) can be approximately equal to k.

2) The zoom head can also use the k simple coefficient, as long as the focus is as close as possible to the fixed focus value. If you focus on two points in this focal length, just remember two numbers.

3) The focal length above 50 mm In actual operation, hyperfocal distance is often more than ten meters, so just follow your feelings. :-)

4) omit k Jane =45.

In hyperfocal distance's case, the depth of field is from the focus to infinity. Under this condition, you can take good photos with large depth of field.

Wide-angle lens is easier to achieve hyperfocal distance, and telephoto lens must be far-focused to achieve hyperfocal distance.

When the lens is in hyperfocal distance state, focus can be ignored and only exposure can be concerned. If the exposure at this time is also set in advance, it is easy to achieve instant capture and the shooting speed will be greatly improved.