An elegant little app to give a wee taste of the TrueDoF range of depth of field calculators.TrueDoF-Intro shares with its sister apps the same core features: A gorgeous interface, ease of use, real-time updating of output and, above all (but conveniently hidden under the hood, as it were), the most advanced depth of field algorithm youll find on the App Store. The TrueDoF range is unique in that its calculations take into account the effects of diffraction. This gives the user a MUCH MORE ACCURATE indication of how sharp the image will be and is a major advance in depth of field calculators.IMPORTANT: Just like every other DoF calculator, TrueDoF-Intro will show depth of field increasing if the f-number is increased. However, at particularly large f-numbers, the effects of diffraction start to intrude significantly, introducing so much blurring that image sharpness standards cannot be met. TrueDoF-Intro, therefore, will show depth of field begin to decrease, or even drop to zero, if f-number is made too large. You will instantly see which f-numbers are too large for adequate image quality. And youll probably be surprised to find that, if you use a camera with a small sensor (smaller than 35 mm full frame), those f-numbers are not very large at all.In use, nothing could be simpler: Depth of field depends on focal length, focus distance and aperture. In TrueDoF-Intro, you set these on the main screen, and the region of acceptable sharpness is shown on the distance display as the region between the two red needles.What is considered acceptable sharpness is determined in this app by the international depth of field standard, so all that the user need do is set the size of the cameras sensor (more advanced versions of the app allow the user to customise image quality standards).A few words on the other apps in the range:TrueDoF is a step up from TrueDoF-Intro. It offers both usability improvements and versatility enhancements, including:* A hyperfocal function - a tap of the HF button sets the focus distance so that the far limit of depth of field is at infinity. While the function is engaged, the focus distance and the near limit of depth of field change on the distance scale as you change focal length or aperture.* Buttons above and below the focal length scroll wheel that allow very rapid setting of common prime focal lengths.* Print/image quality is user-definable. Set the quality standard you desire - the depth of field will be calculated accordingly.* Support for medium format cameras.* An expanded aperture scale.TrueDoF-Pro is in a completely different league.It offers the features of TrueDoF, plus important additions that make the app a great tool for professional photographers and cinematographers:* Focal length presets - set the focal lengths of the lenses you own and use, for even faster selection of focal lengths* Set custom blur spot diameter (circle of confusion), or set print quality* Optional input of focus distance via keypad* Three user-selectable distance scales* Two user-selectable aperture scales* Aperture slider snap to half or third stops* Larger, easier-to-read digital readout display, including (on 4 inch screen) readouts of near and far limits of DoFThese additional features, far from adding to complexity, simply add versatility and allow customisability that actually makes the app much faster and easier and more pleasurable to use - youll never go back to another depth of field calculator.