Is BACK-FOCUS on Red-One ESSENTIAL ??

[George D.]

I realize checking/adjusting the back-focus for each and every lens on a Red-One is supposed to be essential, but in wildlife documentary work it is just too time consuming to do every single time you change lenses. Often times, I have but seconds to change lenses so we can catch the action.

Therefore, if we are not concerned about infinity focus, is it still something that MUST be done each time or we risk jeopardizing the sharpness and focus of the image on the sensor?

In other words, if I am not concerned about infinity at the moment, but MUST change lenses fast, is it really that big a deal not to do a back-focus check?

Thanks.

.

[Colin Sheldon]

If the back focus is off, then all of your markings are off and if it is severe you loose the ability to focus at infinity. Other then that the lens will function.

Checking the back focus with every lens change seems to be a bit on the extreme side.

I can understand daily, or even twice a day. But unless there are large temperature shifts or the lens seems to be out, I wouldn't worry that much about it.


Colin

[Peter Borosh]

George,

Colin is correct in his reply. I just want to add that telephoto lens used commonly in wild life photography have a large Depth of Focus (not Depth of Field) behind the lens. It is only when you would use a wide angle lens or zoom out wide that you will find that you have an issue with focus.

The Red One is usually quite good with keeping Back Focus unless you put an heavy lens on the camera. (My Opinion). Even in extreme temperature, I don't think the mount would change shape too much that the Depth of Focus cannot handle on telephoto lenses.

Pete

[Nick Gardner]

I set the back focus on my red one once, and it was good for the rest of it's life. Traveled all over the world, long lenses, large zooms (optimo etc), extreme hot in africa, very cold on the east coast of the US.

I set my epic once, and haven't touched it since. It really shouldn't change.

Nick

[Jeff Kilgroe]

When you set the mount on the RED One, it should be good under most circumstances for a long time. I always check it when prepping for a new job or after extreme environmental changes. Some people consider that to be overkill, but if you have the tools to check then you may as well.

When you collimate lenses and make sure they are properly mounted, that is something that should be done whenever the lenses are serviced by a lens tech. Typically not something most people do themselves.

Proper back focus (or flange focal depth, FFD) on a PL mount is crucial. Same with proper collimation and maintenance of the lenses. If you are shooting with SLR lenses, then it's a different story, they are typically made with a lot more slop in their design and are more forgiving of tolerances on the mount. But they have their own issues to contend with...

[Colin Sheldon]

I just came off a shoot where we had some back focus issues with the Red One, so I'm a little bit more cautious now, but it definitely hasn't happened a lot.

We tend to just test it during prep... when there is one, haha.



Colin