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Where can I find a tutorial or explanation of this parameter on the camera panel?

These settings correlate to real photography, so I think instead of tutorials, you need information about photography optics and film formats. A good starting point is the concept of the image circle. You can find a good description of it at this excellent web site
Photonotes.org:image circle
You should search there also for 'film formats' and 'lens focal length'
Maxwell settings are very photography based.

Wagurto,

To try to make a quick answer to your point. Since there is no actual film issues in Maxwell, like film grain or tonality the main effect of changing film size will be depth of field in your rendering. This is due to the image circle as Joshh mentioned.

I assume you understand Depth of Filed (DOF) - how much of your background and foreground looks sharp based on your focal point.......

If you use an constant fStop of 8.0 for example you will find that a smaller film size will give you more DOF than a larger film size. So if you like everthing sharp then keep the film around 24x36 (like a 35mm camera), but if you want to really blur out the foreground or background then try changing the film size to 60x90 (like a medium format camera) or 200 x 300 (like a large fromat camera).

Also, keep in mind that focussing very close to an object will result in very little DOF. So if you are doing a rendering of a bottlecap, but want other objects to look sharp too, then try a very small film size of 5x8 and this can help.

adam, that's not technically the relationship... changing film "size" will have an effect on depth of field, but the direct relationship is on the focal length, which in turn affects DOF. Here's a quick primer on filmback size/focal length:




What's important to understand is that the actual Film Back size affects the Field-of-View. Different physical sizes of Film Back, even if they have the same ratio (like 1.85:1) yield completely different fields-of-view. This, in turn, affects how much depth of field is available for the shot. However, in Maxwell, the f-stop (since it's virtual) can be set to just about anything. For most photorealism, though, it's good to keep it within real-world limits for a given lens-size/filmback.



_Mike

Thanks Mike,

Uhhh.... O Yeah......I left that part out. That's what I get for typing this at work and looking over my shoulder for my boss.

I assume it to be easier (understood) to change the focal length (since its virtual too) to get the desired perspective/distortion and keep with apperture settings to those I am used to. I figured a novice can look up lenses from various manufacturers and duplicate them in MW, but not one with a fStop of 100 for example. Then of course go try to find my 5x8 film size !!! I made up.

Everything is so interrelated as you know. I like to set up my Nikon F4 with the viewfinder off and 50mm, put it next to my Rollei 6008 with 50mm and let people see directly onto the focussing screens to proove all this out. They are quickly educated ! What they have a hard time understanding is that both lenses have the same DOF, just different FOV/image circles.

thanks guys I need to star experimenting with this because in theory sounds a little complicate for a novice.

Experimenting is key, but it's really not complicated; these are just the basics of photography, and a huge part of the reason Maxwell renders so photorealistically, if you treat it as such. A few quick experiments and you will quickly discover how to handle the relationships, and begin approaching your scenes like you would with a real camera.

_Mike

Wagurto, for starters imagine that you are using a standard format camera, so no need to mess with filmback settings at all, only fstop and focal length to get the desired DOF. After you feel comfortable with that, experiment also with filmback and see what it does to your image.

Standard format implying what filmback size, Mihai? 36mm x 24mm? There is no actual "standard." That'd be a good starting point, but whatever you want to start with, I strongly recommend it reference a real-world camera, so all your other settings will behave predictably.

Personally, for all my stills, I begin with a "virtual" Canon EOS D1mkII sensor, which is 28.7mm x 19.1mm.

_Mike

Doesn't the D1mkII have a full frame sensor? Yes I ment by standard, 36x24mm sensor size, we have to pretend there is a standard size after all

The large majority of cameras before digital were 35mm film cameras, now with digital all sorts of crops where introduced, but I'd still like to think of 35mm equivalent as being the most widely used "standard" size, and then after that you have all the bigger sizes which are in the medium to large format families.

But a 35mm film camera doesn't refer to its filmback; only the focal length of a "normal" lens (50, or 35 usually.) 35mm film cameras have always had varying film back sizes, which always affected field-of-view/DOF. It's just that a lot of them had 36mm x 24mm filmbacks.

_Mike

This is getting confusing I thought 35mm film is called that way since it's 35mm wide. Why would you use a bigger filmback than 36x24mm (the size of the picture on 35mm film), if you're using 35mm film?

A very informative thread. Perhaps we should start a resource with standard settings for popular film/digital cameras and lenses? Or one better, Maxwell could include these as presets in a drop down menu?

Nik

But if you use the same Focal Length, (35mm) with a smaller or larger filmback, the Field-of-View will be different.

Ok, I think this is why I was confused. Correct me if I'm wrong but if I have a 50cm x 50cm filmback size, but in it I place 35mm film, the resulting image will have the same fov as if I had placed that film in a 36x24mm film back camera, no? I mean it's the light that falls on the actual film that counts, not the size of the film back it's put into.

Well that's a good question, I have never seen that. But if the optics are focused so as to restrict the image to 36x24mm even if the gate is potentially bigger, then yes it'd be the same. But if you somehow had 35mm film suspended in an actual 50x50cm gate, and the optics were set to fill that 50x50, then you'd have a different field of view, which was simply "spilling off" the edge of the film.

_Mike