[RESOLVED] Macro Photography (CG)

[cjwidd]

Looking for tips about setting up macro shots using Corona Camera in 3ds Max. I assume to go about it the same way as you would in the real world, but I am unclear about field of view, focal length, film width, etc. Any advice, tips, suggestions?

[Juraj]

You're correct, the very same thing.

The only difference between 'macro' lens and regular lens in photography is that they can focus in shorter distance (being closer to subject).
But nothing else fundamentally, so you have both 24mm Macro lens, and 105mm Macro lens, cheaper F4 and more expensive F1.8, etc..

So in Corona, you can pretty much do whatever you want. You can do any combination of those values you want, they will always give physically correct result, even if such lens could never be created in real life with our current technological level in optics & sensors :- ).

But some people really like to keep everything referenced, so you can start with common values. Film width is just sensor size, so pick the one you also use in real life, 36mm for full frame camera, 25mm for smaller APSC, etc. larger than that for high-end medium format cameras.
24mm Focal length for wide-angle dynamic perspective forcing you to be close to your subject, distorting the proportions with rectilinear lens. Or 105mm+ for that almost orthogonal peaceful look.

Here is what affects shallowness(/narrowness) of depth of field effect:

Film width/Sensor size: Larger sensor can create more shallow DOF. Full frame > APSC
Focal length: Longer focal length can create more shallow DOF. 105mm > 24mm
Field of View is different measurement of Focal length. While it's more logical than FocalL because you don't have to account for Sensor size, it didn't become popular. You can choose what you prefer to use. 84 degrees is 24mm Lens on Full-frame body. Use one or another. Smaller field if view creates more shallow DOF.
Aperture/f-stop: The smaller the aperture/f-stop number, the more shallow is DOF.

36mm sensor size ("35mm full-frame"), 105mm, f2.8 is common go-to macro lens for people butterflies chasers ;- ).

[cjwidd]

Juraj, thank you so, so much. I really appreciate you taking the time to offer your insight to the process :)

[romullus]

Everything is correct, except for the statement that focal length affects depth of field. This is common misconception, but actually focal legth has nothing to do with DOF. What really affects it, is magnification, i.e. how much the subject fills the frame. If you'll shoot an object at the same magnification, let's say a person filling the frame from head to toes, photograph will always have the same DOF, no matter what focal length, as long as sensor size and aperture will stay unchanged.

Edit: as for macro CGI, if you want physically plausible results, then the most important thing is to keep correct scale of your scene. That is, if you want to render an ant, you must make sure that it is realistically sized.

[cjwidd]

Romullus, in your description is magnification taken to mean the same thing as 'film width' or sensor size?

[romullus]

Not really. Sensor size is... well, sensor size, a physical value that you can't change without changing whole system. Magnification is relative value, it tells you how much of the frame your subject fills. A picture of person that fills whole frame, will have half magnification of picture with person taken from waist. You can easily change magnification by moving closer/farther from subject, or by changing lens focal length. If you move camera closer to subject and at the same time reduce focal length (increase field of view), you can have constant magnification and DOF will remain unchanged.

[Juraj]

Everything is correct, except for the statement that focal length affects depth of field. This is common misconception

I don't think what I wrote is incorrect at all without writing full theory behind magnification and perspective, OP asked what these settings do individually :- ).

The OP asked what the Focal Length does in this case, and Magnification is affect by both distance to subject and Focal Length, increasing magnification can be done by both, either moving closer or using longer focal length, both will decrease depth of field.
Magnification is culmination of Focal Length, Distance and Sensor Size, so it makes sense to write how changing each individually affects the Depth of Field. With DOF, we are always talking about magnification outside of aperture.

There will always be equivalency at which you will achieve identical depth of field with different variables of the system (or across different systems with sensor width).

It would be incorrect if I wrote "Focal Length affects perspective", which is the true misconception many photographers have (and also "zooming with your feet"). Subject shot with 50mm FL will look absolutely the same as from 105mm FL if both camera and subject keep standing at the same position. But that is not how lenses are used in reality, as you keep different distance from subject for each frame of your composition.
Otherwise you could just buy 24mm Equivalent Lens on 150 Megapixel Medium format and you keep cropping the photo to get all other lens :- ). Eventually, that's how all mobile photography will be done which is why they have 64+ Megapixel on ultra-tiny senzor, as the optics have nowhere to advance much.

Should I reframe the statement like this: "Lens with longer focal length will create more shallow depth of field of subject at same composition", because for the reader the result will be identical, but the nit-picking will be worthy of DPREVIEW forum :- ).
Maybe I will just add "from settings in physical camera" so it doesn't sound like what fundamentally creates the DOF effect in physical terms :- ).

[burnin]

:)

From my experience... Considering the word "photography" in the title, keeping knowledge (cognitive process) consistent and theory compliant with real world experience aka practice, Juraj wrote precisely what one needs to be aware of.

Magnification is just too general term in this regard (meaning almost nothing, but plain magnification itself) - especially in macro photography where details matter significantly when it comes to taking a shot by manipulating EV, DOF, focal length, F-stop, lens blur, lens curvature, bokeh, vignette, chromatic aberration, what kind of glass is used... to find the right balance, shooting a pleasing image. One shouldn't strive to be relatively, but absolutely real! But here and now, CGI is just a game, a virtual playground. Go analog, see what you can really create - of real light & matter. Then true understanding comes from being experienced ;)

Perspective, POV changes... and the whole impression of ambience changes with it. Even light, as it is "caught" at & in different wavelengths. 

[cjwidd]

I am misunderstanding what magnification means in the present context. I was under the impression that magnification, as it pertains to photography, describes the relationship between the size of the photographed object and sensor size, in which the object occupying the full sensor is 1:1(?)

[sebastian___]

Usually when the magnification is great, macro photos can have pretty strong chromatic aberration. I think that's a tell-tale of macro shots.

https://vigilantpilgrimphotography.files.wordpress.com/2015/01/imgp0622.jpg

https://www.mjewelry.com/wp/wp-content/uploads/2019/04/watch-service.png

http://ashtontracy.ca/wp-content/uploads/2019/05/cropped-Rolex-Daytona-1-3.jpg

[Njen]

Edit: as for macro CGI, if you want physically plausible results, then the most important thing is to keep correct scale of your scene. That is, if you want to render an ant, you must make sure that it is realistically sized.

This is good in theory, but in practice, it is easy to run into precision issues with Max when dealing with very big or very small numbers. If your entire scene is going to be very small, then make sure you use "good" numbers when choosing a scale to work at. For example, if you are rendering something at an "ant" scale, then it's probably best to choose to use millimetres. If you are working on something like a "house" scale, then decimetres are probably best. If you are working on something "skyscraper" scale, then metres is best, and so on.

[Juraj]

"house" scale, then decimetres are probably best.

Do you know how many architects now cried in horror :- ) ?

Btw I still remember how one professor explained to us in class something like "guys, not we are crazy enough to use milimeters anymore in drawings". That's why I am always annoyed when I download files from russians (like 3dSky) and they model everything in mm, no matter how huge the scene is :- (.

But honestly, very good suggestion I always forget how messy Max can be with precision, boundaries, etc..