DEPTH OF FIELD

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When photograph is taken, a lot of presented elements that are not in the focus appear more or less blurry. But, there is a certain range of unfocused distances where shot elements are presented “acceptably sharp”. This range of distances defines “depth of field”.

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Web-site  http://www.dofmaster.com/doftable.html  (among others), enables Depth of field calculation (i.e.  min. and max. distances in the distance range that allows acceptably sharp vision) - in the function of concrete camera-type (model), chosen focal length, corresponding focal distance and adjusted aperture. 

 

APERTURE

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Aperture represents the opening of the diaphragm and it is described by the fraction number "f/N". But, aperture means more than the value that allows simple “division” of adjusted focal length “f” by 11, 16, etc.. Namely aperture is the key parameter that determines depth of visual field – i.e. distance range of “unfocused objects” that allow its acceptably clear vision (the smaller the aperture the larger depth of field).

 

SENSITIVITY OF CAMERA SENSOR (ISO-VALUE)

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The ISO qualitatively indicates the degree of details that can be precisely photographed: the lower ISO number, the finer details appear on photographs. But, bear in mind that lower ISO number desires much light.

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SHUTTER SPEED (EXPOSURE TIME)

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Shutter speed expresses the speed of shooting i.e. exposure time (time needed light to reach the sensor passing through the diaphragm).

Exposure time is described by the fraction of a second:   1/60, 1/80, 1/125 .... 1/500, etc. The most common cameras (semi-professional ones) usually have maximum exposure time of 30 sec.   

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A lot of practice approved that aperture values of  f/11 or f/16, shutter speed (exposure time) of 1/125 sec and ISO-value of  100 is the best combination to start. But, bear in mind that, in this situation, photo will be very dark (corresponding histogram will have peaks and  will not be centered, but shifted to the left – toward the zones where less texture is recorded by the sensor). Regard to that, mentioned parameters must be adjusted in a a way which allow both histogram  not to have extreme-peaks and to be centrally positioned (or slightly shifted tfrom the central position). In order to achieve that, very often the shutter speed (exposure time) should be changed only.

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If the shutter speed can not adjust the histogram in the previously described way (for example in an indoor spaces that demand 10 or 15 seconds of exposure), it is necessary to decrease  the aperture value - from f/11 to f/8 or f/5.6 etc.. 

Recommended indoor-shooting exposure is 10-15 sec.

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SUPPORTED IMAGE-FORMATS

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Supported picture-formats are: RAW,  JPG and TIFF.

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The RAW format pictures are the most quality ones, beside the fact that they are only influenced by camera sensor sensitivity (ISO), aperture size (f/N) and shutter speed (exposure time). But consequence is too large recorded file that occupies about 20MB - contrary to associated JPG of 5MB only. Previously mentioned is the best proof of extremely high RAW-picture quality: JPG-pictures are acceptable for restitution as well but lost of 15MB causes certain precision decrease (but not significant!!!).

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The second most used format is the JPG and then the TIFF.  JPG allows quality adjustment (as “High” (approx. 10MB), “Medium” (approx. 7MB) and “Low” (approx. 3MB)). The TIFF format images are high quality ones with low compression ratio and, in terms of memory, high capacity one (occupies even 70MB). Because of that, using TIFF images often causes ‘out of memory” problems (because of limited system resources) as well as hard manipulation with such “heavy” files. 

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In order to make compromise between system capacity and requested quality of the pictures, good start is the initial usage of “Medium quality” JPG format pictures (for perspective restitution and 3D-model generation). After that, 3D-model mapping (texturizing) should be performed by using “High quality” JPG format pictures, interchanged with previously used medium ones - under the same names (naturally, these medium- and high-quality JPG pictures must be shot under the same light conditions, using the same shooting parameters, and put at the same disc-place/folder).

More information about described terms, can be found in this  document: TG2 - TECHNICAL GUIDELINE 02/2012: "The Optical System Characteristics".