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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

full frame or not?

S

samuel33

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i haven't got any knowledge in optics can someone answer me:

Red is made to be a full frame camcorder so why have we to make some mathematical things (x1.5 or something) to know what would be a lens on it.
A 55mm would done a 55mm on the Red, no? if it isn't why?
 
Hope you 'll find its useful to learn a little bit from RED One.

Stewart
 
Don't be lazy, do spend some time to read the DVXuser to improve .. they have had discussed it before you asked....

Stewart
 
Full frame ?

Full frame ?

The reason why both are full frame (but different) is very simple.

Still cameras use the 35mm film frame differently than a motion picture camera. One uses the width accross the frame, the other the length. So hence the multiplication factor - but its the same for 35 mm stills photography v's 35mm motion picture cinematography, as it is v's 4K RED cinematography, or v's most modern DLSR stills photography cameras. Or put another way image area of 35mm motion picture cinematography = 4K RED cinematography = most modern DLSR stills photography cameras.
 
Samuel,
every lens projects a circular image on a surface which is xxx mm away from it. the surfsce may be a piece of film or an image sensor. the distance from the lens to the surface (when the image on the surface is in focus at infinity) is measured in mm and it is called the focal length of the lens. now you are free to make use of the sharp image within the circle. some 50mm lenses project a big circle (they are designed for that), so you can easily use them for Hasselblad (6x6 cm image size) as a wide-angle. this way you make most of the available angle with which the lens projects the image on the film. if you choose to take the same lens for 35mm still photography, the part of the circle you use will be smaller, as your image will not be 6x6 cm but only 24x36mm. you use a smaller angle of the available projection and your lens is considered a `normal´ lens for 35mm stills. comes 16mm, even smaller image size, smaller angle - your lens becomes a `portrait´ lens. you are still using the same lens with the same focal length all the way, but you are using different projection angles for different image sizes. when it comes to factors, you compare image sizes and their relations to focal lengths. a 50mm `normal´ lens on a regular 35mm SLR (24x36mm) will behave like a 80mm `telephoto´ on a digital SLR because of it´s smaller image size (sensor), therefore the `factor´ will be 1,6. a digital SLR with a full frame sensor will have no factor.
focal lengths stay fixed, only the angles you use vary.
I hope this was confusing enough - sorry, English is not my native language.
Peter
 
peter roehsler said:
Samuel,
every lens projects a circular image on a surface which is xxx mm away from it. the surfsce may be a piece of film or an image sensor. the distance from the lens to the surface (when the image on the surface is in focus at infinity) is measured in mm and it is called the focal length of the lens. now you are free to make use of the sharp image within the circle. some 50mm lenses project a big circle (they are designed for that), so you can easily use them for Hasselblad (6x6 cm image size) as a wide-angle. this way you make most of the available angle with which the lens projects the image on the film. if you choose to take the same lens for 35mm still photography, the part of the circle you use will be smaller, as your image will not be 6x6 cm but only 24x36mm. you use a smaller angle of the available projection and your lens is considered a `normal´ lens for 35mm stills. comes 16mm, even smaller image size, smaller angle - your lens becomes a `portrait´ lens. you are still using the same lens with the same focal length all the way, but you are using different projection angles for different image sizes. when it comes to factors, you compare image sizes and their relations to focal lengths. a 50mm `normal´ lens on a regular 35mm SLR (24x36mm) will behave like a 80mm `telephoto´ on a digital SLR because of it´s smaller image size (sensor), therefore the `factor´ will be 1,6. a digital SLR with a full frame sensor will have no factor.
focal lengths stay fixed, only the angles you use vary.
I hope this was confusing enough - sorry, English is not my native language.
Peter
Click to expand...

Do you per chance happen to have a link to a visual representation of this? :o
 
Beatniq,
sorry, no graphs
I learned this stuff quite a while ago from a series of books by Time/Life on photography. You could still find them used.
Peter
 
peter roehsler said:
Samuel,
every lens projects a circular image on a surface which is xxx mm away from it. the surfsce may be a piece of film or an image sensor. the distance from the lens to the surface (when the image on the surface is in focus at infinity) is measured in mm and it is called the focal length of the lens. now you are free to make use of the sharp image within the circle. some 50mm lenses project a big circle (they are designed for that), so you can easily use them for Hasselblad (6x6 cm image size) as a wide-angle. this way you make most of the available angle with which the lens projects the image on the film. if you choose to take the same lens for 35mm still photography, the part of the circle you use will be smaller, as your image will not be 6x6 cm but only 24x36mm. you use a smaller angle of the available projection and your lens is considered a `normal´ lens for 35mm stills. comes 16mm, even smaller image size, smaller angle - your lens becomes a `portrait´ lens. you are still using the same lens with the same focal length all the way, but you are using different projection angles for different image sizes. when it comes to factors, you compare image sizes and their relations to focal lengths. a 50mm `normal´ lens on a regular 35mm SLR (24x36mm) will behave like a 80mm `telephoto´ on a digital SLR because of it´s smaller image size (sensor), therefore the `factor´ will be 1,6. a digital SLR with a full frame sensor will have no factor.
focal lengths stay fixed, only the angles you use vary.
I hope this was confusing enough - sorry, English is not my native language.
Peter
Click to expand...

Good morning Peter,

First off there is nothing wrong with your grasp of the english language. Your description of this often talked about subject is one of the clearest that I've read on this site. Just a slight admendment of terms though. The distance between the lens mount and the film/sensor plane is called the flange focal depth and it remains constant regardless of the focal length of lens used. Hopefully your explanation and the ones of others should put this puppy to bed!

Chuck
 
The Flange Focal Length

The Flange Focal Length

More about the Flange Focal Length read and see below via the links and at the picture.

Testing Flange Focal Distance During Prep
http://www.cinematography.net/Pages DW/TestingFlangeFocalDistanceDuringPrep.htm

Focal length and Perspective
http://www.photozone.de/3Technology/demos/focalCompress.htm

Adjasting the Flange Focal Length with Sony HDC f950

Flange_Focal_Lenght.gif
 
So if i have well understand a lens for 24x36 still camera is not the better choice
for the Red i have to buy a lens that is made for the new digital still camera because of the smallest size of their sensor, yes?
 
samuel33 said:
So if i have well understand a lens for 24x36 still camera is not the better choice
for the Red i have to buy a lens that is made for the new digital still camera because of the smallest size of their sensor, yes?
Click to expand...

You don't HAVE to buy a lens made for a digital SLR, you just need to be aware of the difference in field of view between a full frame SLR and an APS-C sized one or a Red. In fact there is an argument to say that you would be better with lenses designed for the full frame, as distortion and vignetting increase towards the outer part of a lens's usable area. Therefore using a smaller crop of the central part of a lens's FOV, you are probably using the better part of the lens.

Nick
 
You may want to check the mechanics of a lens made for digital SLRs: can you focus manually? Can you set f-stops manually? Can you zoom manually? Does it `breathe´ between different focus settings? Is the build good enough for professional standards?
You will be safer and better off by following Nick´s suggestion and get a full frame lens.
peter
 
Hi,

Bear in mind motion picture lenses do not have any adjustment, the lens needs to be adjusted using shims, as does the camera.

I don't think it will be possible to use a depth gauge onto the sensor so an autocolimator (or sharpmax) will be needed to check the infinity setting.

Stephen

The Third Man said:
More about the Flange Focal Length read and see below via the links and at the picture.

Testing Flange Focal Distance During Prep
http://www.cinematography.net/Pages DW/TestingFlangeFocalDistanceDuringPrep.htm

Focal length and Perspective
http://www.photozone.de/3Technology/demos/focalCompress.htm

Adjasting the Flange Focal Length with Sony HDC f950

Flange_Focal_Lenght.gif
Click to expand...
 
Stephen Williams said:
Hi,

Bear in mind motion picture lenses do not have any adjustment, the lens needs to be adjusted using shims, as does the camera.

I don't think it will be possible to use a depth gauge onto the sensor so an autocolimator (or sharpmax) will be needed to check the infinity setting.

Stephen
Click to expand...

Stephen,

the page/picture is from the Operation Manual of Sony's HDC-F950 4:4:4 High Definition Camera that should be the most expensive Cinealta, US $115,800.00 U.S. List Price.
http://bssc.sel.sony.com/BroadcastandBusiness/minisites/cinealta/shoot/hdcf950.shtml

Operation Manual>>Chapter 3-4(E)>>English
http://bssc.sel.sony.com/BroadcastandBusiness/minisites/cinealta/docs/hdcf950_opmanual.pdf
 
It´s understood that zoom lenses for videocameras do have backfocus issues. This could be caused by bad alignment and/or dirt on different camera mounts and also by a change of flange focus distances of one camera due to heat problems while in operation and the fact that these cameras use 3 ccds versus one in Dalsa, Genesis, Arri and RED. Also mechanical stress on the lens during transport can make re-adjusting neccessary. Cine lenses are built to withstand more vibration than video zooms. The are hard-mounted in the camera mount. Nobody questions the flange focal length of a movie camera, if it is off, the camera has had a major accident. If a lens is off, you measure it on a collimator and add or remove shims or use other mechanical means to adjust it.
peter
 
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