How to set back focus

[Mike Krumlauf]

Im having real issues getting the back focus set on my red one.. when my lens is at f3.5 and set to infinity focus, the image is not sharp. im using the sigma 18-250 lens, its less then a month old. how do i know im getting the sharpest image from my camera/lens setup, this back focus stuff is frustrating.

 

[David Battistella]

http://www.reduser.net/forum/showth...on-my-Sigma-35mm-(art)-with-Dragon&highlight=

 

[Ben R.]

Thanks for the details David!

 

[Julio Quintana]

I always found it difficult to nail back focus on my Red One because tightening the two Allen bolts on the side of the mount would always throw the back focus off that I had just finished adjusting. I found the best technique was to loosen the bolts on the side of the mount as little as possible, just loose enough to turn the collar to adjust the back focus.

 

[Scott Crawley]

Save yourself a lot of headaches and bring it to a local tech. There is a saying that goes "If you have to ask..." . It applies here I think.

 

[Julio Quintana]

Save yourself a lot of headaches and bring it to a local tech. There is a saying that goes "If you have to ask..." . It applies here I think.

I'm sure you were trying to be helpful, but there was a time when that "local tech" didn't know how to adjust the back focus and he had to ask someone to explain it to him. I believe that saying you quote is the antithesis of a forum like Reduser.

 

[Scott Crawley]

I'm sure you were trying to be helpful, but there was a time when that "local tech" didn't know how to adjust the back focus and he had to ask someone to explain it to him. I believe that saying you quote is the antithesis of a forum like Reduser.

I am... Trying to be helpful that is. I know this adjustment has to be spot on and it can be very difficult to zero in. I honestly feel that having it done is the best advice for him, even if he has to send it out. I could have been wrong but I didn't think sending him off to toil in futility was the most helpful thing to do.

Edit:
You may be right about the quote, by the way. I've heard many variations of it and I'm not sure what the original is, but the one that comes to my mind first is "If you have to ask you can't afford it." ;-) We have sacrificed so that I can own mine, but I wouldn't trade it for the world.

To to be clear, what I was saying to the OP was; If you have to ask it may be best to have a trained person do it for you. Alternatively he could get himself trained but it isn't a thing I advise trying to learn via internet forum or a YouTube video. My intentions are good, but it is merely my opinion. You may both take it or leave it, naturally.

 

[Stephen Pruitt]

I'm not sure the procedures being offered here are helpful for the RED One with a Canon EF mount, but I could be wrong.

Stephen

 

[Douglas Underdahl]

First videos I ever posted to Youtube:

https://www.youtube.com/watch?v=IhmolBMtDzg

https://www.youtube.com/watch?v=pRicc1HU44c

You can do it, but you must have a Known Good Lens, preferably a wide angle prime. Also a large monitor with Seimens Star helps (download from Google Images.)

If your lens is not sharp, it is likely not the flange focal distance, what us techs call depth, and what camera owners call backfocus which is leftover from 3 chip video lenses. A backfocus that is off will simply shift the focus of your lens so that your focus marks will be off. You will still be able to focus it by eye, which is what most users here do.

 

[Scott Crawley]

I remember seeing these years ago and thinking what a nice thing it was for you to share. I have to say you make it look fairly easy, but I'm still intimidated. I have a lot of respect for the skill and knowledge required to diagnose and set this up correctly.

First videos I ever posted to Youtube:

https://www.youtube.com/watch?v=IhmolBMtDzg

https://www.youtube.com/watch?v=pRicc1HU44c

You can do it, but you must have a Known Good Lens, preferably a wide angle prime. Also a large monitor with Seimens Star helps (download from Google Images.)

If your lens is not sharp, it is likely not the flange focal distance, what us techs call depth, and what camera owners call backfocus which is leftover from 3 chip video lenses. A backfocus that is off will simply shift the focus of your lens so that your focus marks will be off. You will still be able to focus it by eye, which is what most users here do.

 

[Stephen Pruitt]

Doug's videos were terrific for the Nikon mount. Indeed, his Nikon mount was, I believe, the first stills mount available for the RED One. But again, depending upon what EF mount the OP is using, it may not be valid for setting back focus. For example, it won't work for the Birger EF mount since the entire lens mount had to removed to install the Birger (which is what caused the while RED/Birger blow up in the first place).

Stephen

 

[Scott Crawley]

I thought he had one for the Birger as well...

 

[Stephen Pruitt]

The Birger backfocus videos seem to have all vanished into the ether, I'm afraid, and are of no value whatsoever if your Birger doesn't output distance marks (like mine).

Stephen

 

[Douglas Underdahl]

Well the OP says he has a Red One MX with Nikon mount.

Yeah, the Birger was it's own thing; you had to replace the whole front adjustment collar for it to fit and at one time, RED said that it's use would void your warranty AND you wouldn't receive any trade in value!

EOS aka EF mount has shorter flange focal distance so if you have one of these for Red One you might have to remove that collar also, but some just squeaked by and still allowed you to use the collar, I think. Ebay search would turn up examples.

 

[Stephen Pruitt]

Too funny. I saw no mention of him having a Nikon mount. I saw Sigma and immediately (obviously erroneously) assumed he had some sort of Canon mount.

Indeed, in looking over the OP again, I just now saw it at the bottom in his signature. Sorry about that!

Thanks.

Stephen