Brenizer Method, Theory and Practice Introduction
is known that the Depth of Field or DOF for short in English depends on the focal length and aperture used in the following way:
- The lower the number the less DOF \u200b\u200bF, F2 has less depth of field F4 for the same focal length.
- higher the smaller the focal length 200mm F4 DOF in the DOF is less than 100mm F4
The X axis shows the opening of F1 to F22, the Y axis the focal length of 400 to 16mm, the smaller the number the smaller the DOF and the greater the degree of blur obtained. As we see a 50mm F2 lens (Value in the table = 8) has the same level of blur that a 400mm lens at F11 this is quite remarkable and we learn that if we want to increase the degree of blurring our photo shows:
a) Use longer focal length
b) Use a smaller aperture (not always the lens allows)
If a certain scene can be photographed in a certain focal length is clear that with a longer focal length scene can not be grasped in its entirety but it is necessary to assemble a panoramic photograph that is precisely what makes the method popularized by the fotógrao Brenizer Ryan Brenizer.
Brenizer's method is to reduce the DOF of a picture by assembling a panorama using a focal length greater than would be necessary for the taking.
To understand the method we ask the following exercise / scenario: Let a photo
35mm F2 and 50mm are several photos on F2 matching the same visual field as the 35mm photo. What we see is exactly the same in both photos but the DOF is different.
We will see that the degree of blur is larger pan which makes sense because each "frame" of the panorama has a lower DOF than 50mm F2 and the DOF is less than 35mm F2. So what is the opening of our panoramic? Clearly not as the DOF F2 35mm F2 is different from the DOF in 50mm F2 to see the openness that we have to calculate what the aperture is 35mm equivalent to 50mm F2. What
opening 35mm has the same DOF F2 in 50mm?
can search the table, we see that for 50mm F2 value is 8 and 35mm the value 8 corresponds to F1.4. The answer is then F1.4 therefore our panoramic F2 taken at 50mm and has an opening "virtual" blur F1.4 equivalent to taking a single shot on 35mm F1.4
What happens now if we take the scenic with a 50mm F1.4 lens? the result would be an opening below 1.4 and if we took many pictures emulating a much smaller focal length can reach values \u200b\u200bof openness unthinkable. Welcome to the realm of F0.4 and the like. Blurs
for openings as F0.4, F0.5 and others are possible taking enough photos. First
Brenizer method definition
Brenizer
The method is based on the construction of panoramic shots to reduce the DOF, thus increasing the degree of blur of the photo. Using focal large enough to take photos is possible, in principle, the DOF equivalent to any opening that we want even smaller openings to F1.
What lies beyond F1?
Most photographers are familiar with the F-Stops scale used to measure the openness that is: F1, F1.4, F2, F2.8, F4, F5.6, F8 etc. .. This scale is generated by the powers of the square root of 2.
SQRT2 ^ 1 = 1.4 SQRT2
^ 2 = 2 ^ 3 = 2.8 SQRT2
etc ... We therefore add
how to get exposure units (EVs) to calculate the next or previous open, if we Away from F1 we \u200b\u200bfind the following openings (1 stop difference between them):
F1, F0.7, F0.5, F0.3, F0.25, F0.18 ....
These openings are usually impossible with a lens can be emulated by taking into account views that emulate what is the DOF corresponding to the opening and therefore the amount of blur. Applications
method
Brenizer
The method can be used when the photographer wants to reduce the DOF of a shot, reduce the DOF increases the amount of blur by increasing the visual separation between the foreground subject and background. The images take on a three-dimensional, highlighting the funds lost more prominence to the subject. In portraits, product shots and even in some special situations in nature that can produce results that are aesthetically very pleasing.
is advisable to go through the page and Brenizer articles referenced at the end of the article to see that can be achieved with this technique. Grade
Bokeh Blur vs
We have not mentioned so far the magic word "bokeh" and is a good time to explain why. The "bokeh" refers to the visual quality of the areas out of focus in a photo with a special interest in the blur of bright lights. It is a subjective assessment on the quality of defocused areas and therefore has no direct relationship with the DOF or the degree of blur. While it is true that the more blur is in general a better bokeh "blur amount" is not synonymous with "quality blur" and therefore leave this popular photographic concept aside in this article.
Brenizer method in practice
Implement Brenizer method is quite simple, using a focal length longer than necessary for making the maximum possible aperture (smaller f number), focuses the subject and quickly take as many frames as needed to cover the visual field that we want in the final photo. Then based on these frames is assembled pan.
Special considerations:
- If the scene includes people who are there to ask them as still as possible and remove as soon as possible.
- The use of a very low power flash helps to freeze movement and avoid the subject moved to look at one of the frames we have learned, from people or potential movement of the flash is a fundamental tool.
- Programs for assembling panoramas are particularly inefficient if they need to assembly areas out of focus as far as possible each frame should have something in focus and when it is not possible as we seek a very large FOV may be necessary to the assembly of the pan with some degree of manual work by adding points to assemble control areas of focus.
Example:
35mm F1.1 This photo was taken using a 50mm lens with F1.8 aperture but has a FOV equivalent to a 31mm lens, opening is making virtual F1.1 ie it looks like if we had taken with a 31mm lens at F1.1, we see the sudden change of focus within walking distance focused and three-dimensional flower shooting.
The bottom seems endless but it is actually the view from a balcony that has a degree of blur such that buildings and other things you see are simply reduced to shadows in the background.
Those that are not interested in math can skip the next section of the article.
The method in theory
now explain how to deduce and use a formula to calculate the opening "virtual" pan using the method of Brenizer.
The input parameters we use are:
Fi = initial focal length (the lens that we use to take pictures)
Ff = final focal length (the pan)
Ai = initial opening (the one used when taking pictures)
The question is Af which corresponds to the final opening in the pan.
The final focal or Ff can be calculated easily using the panoramic FOV, all armed with panoramic software report the final FOV FOV based on the possible finding that focal length is the FOV. (For example you can use this online calculator )
'll use anything we know about Teleconverters (TC) for our calculations.
know that when using a teleconverter lose light stops, the number of stops we lose an estimated based on the magnification of the TC of the form:
stops = logsqrt2 (Mag)
logsqrt2
Where is the root of logarithm base 2 and Mag is the magnification.
logsqrt2 (x) equals log (x) / log (sqrt (2))
For example for a TC 1.4 is
logsqrt2 (1.4) = 1 and we know that with a 1.4x TC
logsqrt2 lose 1 stop ( 2) = 2 and we know that with a 2x TC
logsqrt2 lose 2 stops (1.7) = 1.53 ie a 1.7 TC lose 1 stop and a half
Using this we can apply the concept of a CT scan instead of bailing enlarge and instead of losing the gains stops (!).
The magnification can be calculated as the
Fi / Ff
For example if we get in 50mm and 35mm FOV emulate the magnification is: 50/35 = 1.4
logsqrt2 (1.4) = 0.97
This we knew because we know that a TC 1.4 "loses" one stop, if we are in the opposite way instead of losing a stop we won.
words, take on 50mm to 35mm emulating "win" by 0.97 stops of light. We turn now opening
initial EVs.
logsqrt2 Ev = (Ai) Example
If Ai = 1.8 then
logsqrt2 (1.8) = 1.69 to 1.69
EVs
Then we can subtract 0.97 to get the amount of virtual EV as we are winning the light which EV is lower.
logsqrt2 Ev = (Ai) - logsqrt2 (Ff / Fi)
In our case
logsqrt2 Ev = (1.8) - logsqrt2 (50/35) Ev = 0.72
Ev And we can convert to open using the power of root 2
SQRT2 Af = ^ (V)
SQRT2 ^ Af = Af = 1.26 0.72
which brings us to our final formula:
SQRT2 Af = ^ [logsqrt2 (Ai) - logsqrt2 (Fi / Ff)]
Simplifying:
Af = Ai / ( Fi / Ff)
Applying the formula in our example:
Af = 1.8 / (50/35) Af = 1.26
So if we get in with a 50mm F1.8 enough pictures for the panoramic equals a 35mm blur and DOF are those who would see with a 35mm lens F1.26
Acknowledgements We thank Gabor told me many key concepts to write this little article.
Special thanks to Ryan Brenizer person who helped with some basic data for the theoretical part of this article. References
Home Page of Ryan Brenizer
photostream on Flickr by Ryan Brenizer
Brenizer Blog entry explaining the method and with great photos
Brenizer Video Blog explaining how to make panorama fast
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