OTOY Forums

cFrank78, as Roeland mention, You have to get horizontal camera direction in order to avoid vertical lines converging and Your problem will be solved..now what about those numbers.. I could advise one thing to remember in the end: it doesn't have to be right, it has to look right! =)

I dont get what you guys say - sorry!

In post NR 5 is picture 21.jpg - 2 bottles - 3 pictures - 3 focal lenghts. 18,34 and 55mm. I added the scene scaled correctly as a rar file. Try it in Octane to get results like in picture 21.jpg with my modeled szene. If you get the goal, i know its possible but at the moment i think octane has some big problems. I tried it yet for hours but MAN...why is this so complicated in Octane or am i too stupid? You have the szene/rar and the picture how it should look like. Please try it by yourself!

Regards Chris!

I'm in agreement with cfrank78, the camera system in Octane needs some work to be more user friendly in regard to how it is setup vs other major software packages AND real world cameras. We shouldn't have to do math equations to figure out how to set the correct focal length based on FOV, there should be a focal length slider with ticks marked for the most common focal lengths.

Another camera problem is the F-Stop does what it's supposed to do with making the image darker the higher the F-Stop goes, but it does nothing in regards to the intensity of the depth of field as it would be on a real-world camera, this is handled by Aperture in Octane. The higher the f-stop the more depth of field there should be(less blurry), lower f-stop the less depth of field (more blurry), it makes no sense as to why this part of F-stop was split into the aperture control. In fact Aperture and F-Stop should just be combined into one slider that handles both brightness intensity & DOF so it mimics physical cameras... which would also make one less slider to worry about.

I love this program and the more I use it the more I love it, but the octane camera system is something that needs to be finessed.

Octane doesn't model fish eye lenses or the barrel distortion you usually get with very wide-angle lenses (note that the right edge of the red bottle is not straight in the 18mm picture). So the images are never going to match exactly.

To get the same perspective your objects need to be in the same position in the render. In your pictures the blue bottle is standing against the wall. In the renders it is some distance in front of the wall.

About the impression that your bottle is a huge building: you get this because the camera position is set lower than in the pictures and it's looking up. An 18mm lens will create a lot of distortion in that case. Put your bottle on the edge of a table and take a picture with your 18mm lens from the same height as the tabletop, you will get the same effect in this picture.

The formula for the horizontal field of view angle is 2 * atan(sensor width / 2 / focal length))
For a 35 mm camera this yields
18mm → 90°
34mm → 55°
55mm → 36°
85mm → 24°

But there are various other camera formats out there. For a four thirds camera (sensor width is 17.3mm)
18mm → 51°

So a focal length slider isn't that straightforward.

The fact that changing the depth of field also changes the exposure is a limitation of how cameras work, I don't think it will be convenient if we emulate this in Octane.

--
Roeland

cfrank78 wrote:I modeled the objects in Rhino in mm and then imported them in octane - also in mm!

ok, this seems to be right. as roeland noted, the distortion comes from the strange camera position in octane - led me to think that the scale was wrong. you have placed the camera a few mm above the ground, where the real camera is about 10cm above the floor, right?

cfrank78 wrote:I made an object and put it in octane again and the results were the same. Try it yourself. I added the scene as an obj with the 280mm bottles. Try to get the picture and the perspective like in the photo 21 in the earilier post. I really hope you reach the goal and tell me how you made it! I am desperated here!

i did it: BUT those 18/34/55mm numbers are maybe not the complete truth either; what is the crop factor of the camera? here is a page, that calculates h/v fov for some camera types, and you'll notice, that the actual field of view is pretty different depending on the sensor: http://www.howardedin.com/articles/fov.html

anyway, you will still not get a perfectly matching result for wide angles, since octane has no zoom lens changing fov only shifts the perspective. octane is like a fixed lens, where you can artificially change the field of view (what a real camera can't do). to match wide angle photography, octane would need to have another camera model.

cfrank78 wrote:Also......how did you get this strange numbers? 111 and so on. Which plug in do you use? When i google and calculate the Full Frame 28x36mm Sensor at 18mm it gives me 99,34° angle, not 111,1. But nevertheless - 99 and 111 still make not much difference.

as i said: this "strange" numbers are based on another artificial camera model (from daz studio); i'd only wanted to show, that there is not only one correct number for the horizontal fov, as it is based on a number of factors. btw, the tests were done in daz studio, where i just entered the focal lengths above. i did another series using a crop factor of 1.5: imo these are matching the original photos better; of course still not matching the distortion for wide angles...

goumz wrote:Another camera problem is the F-Stop does what it's supposed to do with making the image darker the higher the F-Stop goes, but it does nothing in regards to the intensity of the depth of field as it would be on a real-world camera, this is handled by Aperture in Octane.

you are right, but we still do computer graphics, do we? imo it is pretty useful to control fstop and dof independently, and i bet every camera owner would love to do that too - as it is just impossible in real world.

my personal critisism would be, that exposure, fstop and iso do pretty much the same with diffrent factors - or is there something i'm not aware of, roeland?

photographers use software to get rid of distortions. if You aplly these filters in inverse manear on untouched render out image, You should get pretty much what camera sees, but..with expence of quality decrease.

Hi Everybody!

Thank you all for your help an time!

T_3 you made the pictures. Thank you. But the "horizont" in your picture is straight. The original pictures in post 5 are not straight, at least the horizont. Have a look. I made my pictures exactly like the horizont was. I placed the camera so that the horizont and the object itself were like on the picture. The 3 pictures were made with a full frame camera 24x36mm.

When you trigger the FOV slider - it works like a perfect zoom. 1= completely zoomed in, 180 = infinitely. In the real photography, infinity is not possible. It is physically not possible. So if you wanna bring 180° onto the sensor you have to distort the picture like for example in the ken rockwell picture=fisheye. Or look at some panorama shots where you stitch 6 pictures to a 180° panorama. The Problem with octane is, that if you take a wide angle, octane just zooms the objects extremely far away, which should not be! If you look at real wide angle pictures the objects are not zoomed so extremely far away, they are just distorted and just look like as they would be a bit more far away. So if you trigger the sliders like this, you have absolute no chance to get your picture like a real world wide angle picture....you have to guess play and save it as a png, then import it into photoshop and do the rest with distortion tools in photoshop! Not good! I tried is yesterday 7 hours. Absolutely no chance!

Reoland you mentioned that it is not a comfortable way to use the aperture like in the real world, cause the aperture would also afect the exposure. your right. it is very comfortable to use the aperture slider without affecting the exposure. BUT....i think you missunderstood our real problem. For example if you watch the imager tab in octane:

Exposure
fstop
ISO
gamma

exposure= darker, brighter
fstop= exactly like exposure - darker, brighter - so completely useless
ISO = brighter, darker - like exposure and fstop. 3 sliders. 1 is needed.
gamma=gamma=contrast for "lights"

For beginners that did photography a lot of years like me and for people who are used to vray, arion,....completely confusing!

In the real world:
Exposure = time that the shutter opens/closes and lets "light" on the sensor
fstop = Aperture = how big the "hole" in the lens is, that lets light through the lens and on the sensor and also generates the depth of field.
ISO= how sensitive is the sensor. LOW ISO = not much sensivity but very high quality an low noise and a high dynamic range of about 13 apertures from high to low in modern dslr. High ISO like for example 6400 = very sensitive = low dynamic (8 apertures), more (much) noise but very effective if you wanna catch bright lights AND dark areas, for example if you do indoor shots with a window in it or shots at a concert with lights in the background and so on!

I hope now you see what the confusing part is. You are right reoland, if you say that it is comfortable to work with depth of field without affecting exposure, but everything we know, we learned, is compeltely wrong in octane. We have to think completely diferent and thats what octane makes so complictated. If you are a director or a camera man or a photographer you are used to those values and you know how to work with them and you know what you have to do to get good results!

If i wanna make a impressive shot of my jewelry i know i have to take 60mm or 85mm, take an iso of about 400 and a macro glass with a aperture of about 13 for a good depth of field. Position the camera, put some lights, klick and voila, great shot. It is very fine to play with DOF without affecting exposure BUT what we mean is, that the numbers - the values are so strange. Exposure 1/100 should give the results that in the real world 1/100 would give. the NUMBERS are so confusing. fstop ....give us aperture values. F1,4 - F2 - F2,8 - F4 - F5,6 and so on!

I want a wide angle on a Full Frame. Give us focal length like 14mm, 18mm, 24mm, 35mm, 50mm, and so on. We can read that . We all learned that. Thats our business

Your user group are people that are used to those numbers. This is our business.

If i were a professional race car driver and i am used to km/h or miles / h - would you wanna give me my tachometer in mm/sec? You know now what i mean?

You have 3 sliders that do the same thing and only ONE of the is working like in real world. I hope i made my problem clear now and you guys understand me better!

Have a nice day everybody - Chris!

hi Chris,
as a photographer in the far past and a maxwell user in the past, i was a bit confused two years ago when i start to work with octane, but after a couple of months i found it confortable. sometimes, less fidelity but more flexibility is the right choice.
i agree with you that the f-stop value in the camera imager is useless, but i love to use the iso value a lot.
in general, for internal/external architectural shots, i set the exposer for the exterior at 100 iso and then rise the iso value for interior to 400/800 without changing the exposer value. this is just one way, probably other users have different ways
about the fov question, there are a lot plugins for every host application for doing perfect matching of real photo with a 3d view and can be easily exported to octane with no issue.
sometimes we all forget that octane is just a render engine, not a complete 3d generalist application, the best in my opinion bat always a render engine at the end
ciao beppe

about the fov question, there are a lot plugins for every host application for doing perfect matching of real photo with a 3d view and can be easily exported to octane with no issue.

Hi Beppe!

Thank you for your answer. What are sutch plugins? Can you post a view links? I would really be interrested, cause i have now about 30 requests by photographers that sent me compositings and want me to render tables, chairs, tv´s and so on, that fit perfectly in their scene with matching light and shadows!

Another question:

For example i have a 3:2 1024 x 786 picture i made in photoshop. Is there a possibility or a workflow to put this picture as a background in octane to match my imported 3d objects as good as possible in the sceen and wher i allways have shown that (non moved) background image? that would make my life much easier

Kind regards Chris!