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Red 18-50 Question

Rick Darge

Rick Darge

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Hey Reddddders,

Question for all you out there with the 18-50 zoom..

Ok, you zoom in at 50mm, you focus on your subject.. Then you zoom out to 18mm.. Your subject is now soft.. you focus your subject at 18mm.. You zoom back in to 50mm, your subject is soft.. You focus at 50mm, you zoom out, slightly out of focus, you zoom back in to 50mm, everything is good since the focus was set for 50mm..

Normale ?
 
This is the difference between true zooms and 'variable primes'.

A zoom will hold focus as you zoom out, unless the flange depth (aka backfocus) is out.

It's a compromise made for this lens at this price point.
 
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That's what I thought Nate.. I just wanted to confirm this fact with other Red zoom owners.. The more I use this camera, the more particular I become about every little aspect :holloween:
 
NateWeaver said:
This is the difference between true zooms and 'variable primes'.

A zoom will hold focus as you zoom out, unless the flange depth (aka backfocus) is out.

It's a compromise made for this lens at this price point.
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This is not quite correct Nate. Arri make a set of vari primes and so do some other cine companies and they all hold focus through the zoom. All that "variable prime" means is that the lens has to short of a zoom to be very useful for actual zooming.

RDG what you are seeing here is how a still zoom mechanics work. Still zoom lenses do not compensate to hold focus through the zoom like a cine zoom mechanics are built to do. Hence the reason why still zooms are not the best choice for cine use and why the red zoom has no witness marks. If a person wants to use still glass for cine use primes are the best choice.
 
Finner said:
This is not quite correct Nate. Arri make a set of vari primes and so do some other cine companies and they all hold focus through the zoom. All that "variable prime" means is that the lens has to short of a zoom to be very useful for actual zooming.
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Aha. I was under the impression that the Arris in particular did not, in exchange for better optical qualities than they otherwise would have if they were true zooms.
 
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Finner, are you saying the Red zoom is not sufficient, equivalent to a still lens?if that's the case, why did I spend $6500 on this lens rather than just buying a rehoused Nikon PL prime set?
 
rgdfilmsRED said:
Finner, are you saying the Red zoom is not sufficient, equivalent to a still lens?if that's the case, why did I spend $6500 on this lens rather than just buying a rehoused Nikon PL prime set?
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Take you lens to a reputable lens tech - your camera's may also be out of whack, which with the new mount is easy to fix. If the lens is indeed out of calibration send it back to Red. Repeat until they send you a good one.

A checkup with with a good lens tech should be considered essential on any new or used lens you buy.

Matt Uhry
www.mattuhry.com
 
Richard,

I enjoyed meeting you this past week.

As Matt said, have a good lens technician check out all lenses you buy, whether new or used. Your particular 18-50 could simply need to be calibrated. You could also have a PL mount that needs some adjustment, thus your back focus may be off.

That said, my RED 18-50, which is collimated correctly, and used on the upgraded PL mount on all six of our RED cameras, holds focus well throughout the zoom range.

Again, my guess is your lens or mount needs some adjustments.

How many recorded shots are you going to be running through the whole zoom range from 18mm to 50mm, or vice versa? If you're focusing by tradtional cine methods, and you have a monstrous full zoom range shot to take, then wandering focus through a zoom could be a problem. But if you're sight focusing as the operator, and you faced a situation like that, a simple rack of focus could correct it.

On this forum you'll find that traditional focusers necessarily seek hooks, tapes, accurate lens markings, etc. - and they should for their methods of operation. But sight focusers aren't worried about hooks, tapes, ACs, or hyper-accurate lens markings for their sight focusing needs. They use and trust the electronics in RED ONE. Both methods are valid, and each is a workflow choice. I use both at times, and yes, I've worked with Finner and Matt Uhry on a couple of professional projects. These guys know their craft, but as you know, my approaches to using RED ONE are usually different then theirs, although sometimes similar or identical. You need to realize that the field workflow or tech advice you get on RED User (or elsewhere) is filtered through the experience of the person giving the advice.

After six months of heavy use of the 18-50 my opinion is that it is a very good lens for the price - its performance to price ratio is very good. If you wanted perfect zoom action, lens markings, etc. in a short cine zoom, you could have opted to pay 5 or 6 time what you paid to get that.

Traditional cine shooters are used to well defined workflows and mechanics of the lenses they use. But RED ONE is now, and will increasingly be used by professionals who come from the other professional imaging disciplines: still photography, television, and video. Those other pros expectations and field workflows will be different as will their approach to using RED ONE. Their alternate approach is perfectly valid for their work.

Finner and Uhry were invited members of my LART team. They tested a lot of lenses, including the 18-50. Here's a paste of their analysis of the RED 18-50 which they submitted to me, and I posted on the LART forum, along with my endnotes on the 18-50:


Red 18-50 Zoom
PRO's: Very sharp, minor barrel distortion at wide end (much better then many wide zooms though), Minor chromatic aberration in corners (again better then many lenses out there), Does not flare easy and very neutral tone with glass and lens coatings, Very little breathing.

Con's: Focus scale quite short (better then stills lenses but worse then cine), No focus witness marks, Slight image shift due to lens moving inside housing, Mechanics are weak and do not compare with cine lenses.

Conclusion: Better mechanics and ease of use than a stills lens but not in the same league as cine lenses. Please note RED 18-50 $6,500 compared with cine zooms of same focal length costing more then 6 times as much.

Gibby note 2: I've owned and used widely the RED 300 and RED 18-50 for almost five months now. Though the 18-50 has the mechanical use nuances mentioned, I've been completely happy with the results of the images from it. My 18-50 has been used widely in about every genre and style of production except narrative cinema. My RED 300 has also been an excellent lens: crisp, clean, and accurate. It was my 300 tested by Matt and Finner, and I also believe it was my 18-50. Matt and Finner do a lot of cine-style production, whereas I do a lot of EFP style production, with a moderate amount of cine-style. The challenges they mention in mechanical use of the 18-50 have not been drawbacks for most of the work me and my crews have done with it - EFP, underwater, aerials, mobile cine style, etc.
 
If the lens is sharp zoomed in and goes soft on the way out, that should be the back focus but you first need to make sure your depth is set first on the camera. My 18-50 is good but I had another customers here that was out.
 
It sounds like it could be a simple back focus adjustment.
Although, I have yet to see a RED 18-50mm and I am not certain as to how the focus mechanics work.

I agree with what others are saying about price-to-quality balancing.
You can pay ~$6,500 for a nice lens from RED, or you can pay upwards of $50,000 for an Angenieux 15-40mm Optimo.
Is it worth +/- $35,000 more?
In my opinion, yes... lol
But that's just me. I've been looking at and servicing lenses every day for the past 6 years and appreciate a well composed coalition of aluminum and glass.

If a back focus adjustment is in fact the only problem, the lens is no worse than that with a five-figure price tag. Even the big-ticket optics require adjustment from the factory. For the record, I do not accede to plugging specific businesses exclusively:innocent: , but I would suggest a quick check and service at a lens shop.
 
It is likely that the back focus (flange depth) is wrong. But this is where I don't like the idea of people just resetting their camera's lens mounts. Because what you don't know is whether the mount is set wrong on the camera or the depth is set wrong on the lens. Simply adjusting them to one another is like chasing your tail, and it means that (1) you're going to have to redo it for every lens and (2) you'll never know if you're right until it's too late, especially on wide lenses.

You need to have your lens checked on a collimator to make sure it is set to proper depth. This is an absolute standard. Then you can set your camera to this and everything is correct. Even Jim noted that the lens mount depth is not something to be changing in the field.
 
Thanks everyone for the feedback. For the record, I really love the Red 18-50 zoom. It's a great little lens and very lightweight. Makes really silky smooth pictures.. Now if I could only get it to match focus, all would be good.. It was nice meeting you as well Gibby, I'll see you at NAB
 
rgdfilmsRED said:
Finner, are you saying the Red zoom is not sufficient, equivalent to a still lens?if that's the case, why did I spend $6500 on this lens rather than just buying a rehoused Nikon PL prime set?
Click to expand...

I definately did not say that. Very few still zooms hold focus through the zoom length so for cine shooting in theory a still prime should work better then a still zoom (testing still lenses against each other is a must to determine this.). I have felt that the red 18-50 is a rehoused sigma 18-50 for quite a while now but recent findings from a person that dropped and broke open a 18-50 have shown there is much more to that lense then just a simple rehousing and that rear elements seem to be situated differently then the sigma. Because of my belief that the lens is a rehoused still lens is why I suspect there are no witness marks on it. Please note for $6,500 there is no new PL option by any other company anywhere even close to that price.

Gibby said:
You need to realize that the field workflow or tech advice you get on RED User (or elsewhere) is filtered through the experience of the person giving the advice.

Traditional cine shooters are used to well defined workflows and mechanics of the lenses they use. But RED ONE is now, and will increasingly be used by professionals who come from the other professional imaging disciplines: still photography, television, and video. Those other pros expectations and field workflows will be different as will their approach to using RED ONE. Their alternate approach is perfectly valid for their work.
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This is one of the best descriptions of opinions that I have heard here. I own a cooke zoom and I love it but for some people that own optimo zooms my cooke would be a POS.

It's simply all about whats best for your type and style of work.
 
Matthew Duclos said:
It sounds like it could be a simple back focus adjustment.
Although, I have yet to see a RED 18-50mm and I am not certain as to how the focus mechanics work.

I agree with what others are saying about price-to-quality balancing.
You can pay ~$6,500 for a nice lens from RED, or you can pay upwards of $50,000 for an Angenieux 15-40mm Optimo.
Is it worth +/- $35,000 more?
In my opinion, yes... lol
But that's just me. I've been looking at and servicing lenses every day for the past 6 years and appreciate a well composed coalition of aluminum and glass.

If a back focus adjustment is in fact the only problem, the lens is no worse than that with a five-figure price tag. Even the big-ticket optics require adjustment from the factory. For the record, I do not accede to plugging specific businesses exclusively:innocent: , but I would suggest a quick check and service at a lens shop.
Click to expand...


RDG I can not recomend the Duclos team highly enough. Paul was accommodating, extremely precise, very favorably priced and a pleasure to deal with. Matt recomended them to me and when I was in LA for LART I had them do some work on my cooke. I hope you take down the lens and your camera to them and would be really interested to hear the results. You may even be able to have them engrave focus witness marks on the barrel as this would be a big benifit that the lens currently does not have and may be part of the reason why it is so much cheaper then other current similar cine versions. I would also be interested to hear about how the T-stops hold up and you could get them to test that there as well. Please note that every cine zoom lens is not 100% truely accurate with its T-stop marks as all are slightly off, most being off by very miniscule amounts. There are actual tollerances that are acceptable for these differences. I would be very interested in hearing how your lens fairs with that testing also.
 
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