ba­sics: cam­era lenses

For the next in­stal­ment of our Ba­sics se­ries, let’s start ex­plor­ing the cam­era

3D World - - CONTENTS - Mike Griggs Mike Griggs is a 3D and vis­ual ef­fects artist with vast ex­pe­ri­ence across the in­dus­try, as both a cre­ator and a tech­ni­cal writer. www.cre­ative­bloke.com

Which lens is best for the job?

If you’re new to CGI, you may feel that there are far too many tools to choose from in a dizzy­ing ar­ray of soft­ware. This se­ries aims to break ev­ery­thing in CGI down to the very ba­sics, so that ev­ery artist can be armed with the knowl­edge of which tool is best. This month we start our look at cam­eras and lenses.

The cam­era is prob­a­bly the sin­gle most im­por­tant tool in the world of CG. It is more im­por­tant than mod­el­ling and an­i­ma­tion and if the cam­era is point­ing the wrong way, even the light­ing won’t be seen. There­fore, mas­ter­ing how 3D soft­ware han­dles cam­era ma­nip­u­la­tion is cru­cially im­por­tant.

Over the next few in­stal­ments of the Ba­sics se­ries we will look at the var­i­ous func­tions of cam­eras in dig­i­tal con­tent cre­ation. To start with, let’s ex­am­ine the def­i­ni­tion of a cam­era in CG.

One of the most com­mon as­sump­tions for a new artist work­ing in CG is that the per­spec­tive view is the cam­era. While ‘tech­ni­cally’ true as the soft­ware has cre­ated a vir­tual cam­era to view the scene in the view­port, this is not the same as an ac­tual cam­era ob­ject.

A cam­era ob­ject is usu­ally iden­ti­fied as a film-style cam­era wire­frame in the view­port, and typ­i­cally has a prop­er­ties palette full of in­for­ma­tion which makes it anal­o­gous to real-life cam­eras.

The most im­por­tant of these fac­tors is the fo­cal length in­for­ma­tion, as this de­ter­mines the zoom or field of view (FOV), and this dic­tates what the cam­era is see­ing. Learn­ing about fo­cal lengths and how they can be used for scene ma­nip­u­la­tion is in­cred­i­bly im­por­tant for mak­ing shots be­liev­able in terms of scale, and once this has been mas­tered it can be­come a great tool for ma­nip­u­lat­ing images for more fan­tas­ti­cal briefs.

Most CG cam­eras de­fault at a fo­cal length of around 35mm, which is a very com­mon fo­cal length for cam­eras as a ‘do all’ so­lu­tion. How­ever, if the scene is of a por­trait of a CG head bust for ex­am­ple, then a 80-100mm fo­cal length would be more suited, as the longer a fo­cal length the less per­spec­tive dis­tor­tion oc­curs, mak­ing the bust look more re­al­is­tic.

Nat­u­rally the best way to learn about fo­cal lengths is to use an ac­tual cam­era, and this knowl­edge will eas­ily trans­fer to your CG projects.

01 View­port CAM­ERA

Although most dig­i­tal con­tent cre­ation ap­pli­ca­tions al­low ren­der­ing in any view­port, this is not the same as hav­ing an ac­tual cam­era ob­ject. A cam­era ob­ject usu­ally has a lot more op­tions for con­trol­ling fo­cal length, and as it is an ac­tual ‘ob­ject’ in the scene it makes an­i­mat­ing it a lot eas­ier. Some ap­pli­ca­tions al­low the de­fault front, top and side cam­eras to ac­tu­ally be seen and ex­ported, but be mind­ful of these as usu­ally they are best kept hid­den.

02 Wide-an­gle lenses

Wide-an­gle lenses (which tend to be classed as any­thing lower than 35mm) are good for wider scenes as they can catch a lot more de­tail. They are not great for close-up work as they dis­tort fea­tures, so are un­flat­ter­ing for char­ac­ter work. Ex­treme wide-an­gle lenses are com­mon in ar­chi­tec­tural work, but be mind­ful to straighten ver­ti­cal lines; this ef­fect can be achieved with tilt-zoom lenses, com­monly used in high-end ar­chi­tec­tural pho­tog­ra­phy, but can be re-cre­ated eas­ily in soft­ware.

03 tele­photo lenses

Lenses that are longer than 50mm tend to be called tele­photo lenses and are com­monly used for char­ac­ter and close-up work, but they also tend to be used for macro work. Most por­trait work is done in the 80-100mm range.

Ad­di­tion­ally, long tele­photo lenses in the 150-200mm range can be great for cer­tain types of scenes as they can be used to cre­ate in­ter­est­ing con­trasts be­tween the fore­ground and back­ground.

04 us­ing Zoom lenses

Zoom lenses are of­ten seen as the ‘poor cousins’ of prime lenses which have a sin­gle fo­cal length, but good use of zoom lenses in a scene can be a great way of achiev­ing some cre­ative ef­fects and looks. The ground-break­ing space­ship work in the TV re­boot of Bat­tlestar Galac­tica de­pended on zoom lenses, and they can be used to cre­ate a dolly zoom ef­fect – a tech­nique in which there is an ob­ject in the cen­tre of the screen while the back­ground ap­pears to zoom in or out.

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