Back focus or flange depth

Nowadays a shallow depth of field is often demanded in film and television productions, in order to achieve the so-called “film look”. Here the subjects, for the most part in the foreground of the picture, are presented in sharp focus, while the background is kept out of focus (this is used as an artistic tool to emphasise certain features).
To obtain this film look the cameras used are usually digital cameras with a “single sensor”. The effect is rendered more telling, the bigger the sensor is.p>

With increasing resolution (SD, HD, UHD or 4K) particular care is needed when selecting the equipment. Equally it must be ensured that the back focus is absolutely right both from the camera (picture window/sensor levels) to the rear lens element, as well as the other way round. For zoom effects it is true that the optimum focus lies at the same level over the whole zoom area: That is where the light-sensitive layer of film roll or the image-converting layer of the sensor lies. If there are variances here, if the indications on the lens dial (focus ring) in focussing on the set do not agree with the distance of the lens to the image – the object will not be in focus.

In order to ensure that the back focus is right, there are a number of options for measuring it.

Chrosziel has offered proven technology for a number of years. With the Chrosziel Collimator C-LTB MKII the most precise of measurements can be taken.

With the Chrosziel Projektor P-TP6 too (from summer 2015) the back focus can be checked. In addition the projector allows for a visual check of a number of parameters, which make a statement about the validity of the optical effects checked.

The Chrosziel lens testing instruments (LTI) are tried and tested and have been used for several years, they have been continuously developed and distinguish themselves through their outstanding precision and robustness. Chrosziel has a variety of lens mounting versions available for the relevant optical formats.

Your benefits: the lens mounting versions suit the collimator and the projector! So one investment pays out twice the reward.

Contact us! For questions about our collimator or our new projector, we are available and happy to speak to you on +49 89 901 091-0 or answer your mails at info@chrosziel.com zur Verfügung.

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