Brevis soft focus issue, help!

Clay. When I can, I bring a focus chart to the set when I set up. When it is inconvenient I use a variety of ways to focus. However setting up on a focus chart with your video camera wide open will show you exactly what you are really photographing and you will often see that the best focus at the center is not the same as at the corners. I
Once you get used to finding a best mid-point focus (often a hair past the center) then you can figure out how you like to do it best. But you should learn your adapter on your camera.

I always double check my focus on a real picture. Sometimes I think i set everything up perfectly, look through the lens and its soft. Maybe it got bumped a touch. Dennis says it can change with temperature. So I will sometimes adjust by eye in a 17" monitor.

I know this is different than most manufacturers tell you to do it, but for me its been more accurate.

Lenny
 
Sounds pretty ballsy to do it that way. I'm working on a 15 day shoot, sometimes shooting for 10 hours at a time while switching from sticks, to a jib, to a dolly and back again (switching base plates)... so just being conscious of it wouldn't be enough i don't think. I'll play around with it though.
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I've used gaff tape before and even though it held the ring down firmly the camera slowly started to misadjust. Don't trust electronic focus to stay exactly where you left it. After turning the camera off and on and temperature changes the backfocus will start to shift slightly and you may not notice it until a bunch of your footage ended up soft. I check my backfocus at each setup change. It takes about a minute but is well worth it.

The edge softness I see in your stills should not be happening. I don't know what I would recommend except to add even more spacers (just look at the huge spacer tube that the SGpro comes with to prevent edge softness). Unless your achromat or ground glass is defective I would blame your HVX. The lens isn't as problematic as the EX1's but it definitely requires a workaround when using adapters.

Marco
 
ClayM said:
Sounds pretty ballsy to do it that way. I'm working on a 15 day shoot, sometimes shooting for 10 hours at a time while switching from sticks, to a jib, to a dolly and back again (switching base plates)... so just being conscious of it wouldn't be enough i don't think. I'll play around with it though.
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Thats what an AC is for :)
I use cam tape and write ALL settings on the camera both on the LCD and on the barrel next to the zoom (Z number/Focal Length, ect). It serves as a visual aid and as a reference for anyone near camera, whether I'm the DP or AC, the settings are always double checked before rolling. So gaff is never needed unless hands are around camera during the shot.

I had this same issue with my Brevis. I removed the achromat from the barrel and the lens mount and realigned while pointing at a chart. I fixed the sharpness slightly on the corners but it still had that warped, soft look on the right side (primarily the top corner). It was good enough for the remainder of the day. I think that with time, you have the adjustments necessary on the Brevis, but it can be difficult to nail edge to edge with those set screws.

I completely agree with lenny. I use the zoom feature on my pana monitor (I have the 8.4" model) and it does a superb job for focus between corners and center. It also depends on what the DP wants. For music videos, I have been asked quite a few times to keep sharpness biased toward the center, which is their decision. Regardless, there is a happy middle ground that can found, especially if you're on a particular focal length.
 
marco0782 said:
The edge softness I see in your stills should not be happening. I don't know what I would recommend except to add even more spacers (just look at the huge spacer tube that the SGpro comes with to prevent edge softness). Unless your achromat or ground glass is defective I would blame your HVX. The lens isn't as problematic as the EX1's but it definitely requires a workaround when using adapters.
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It's not the HVX. Like I mentioned earlier I hooked the Brevis to another HVX, with the same exact results.


My footage looks nearly identical to the softness that is seen here in Lenny's chart test.

http://www.leonardlevy.net/HVX200 wOrig Brevis, SGPro (Rev2)/HVXop_Br_N1,4_22FC.pdf

And before somebody claims that its because the HVX is wide open in this test, I've found that the edges I'm getting don't change at all as the HVX is stopped down.

Here's a picture of my setup with the spacers in

DSC_9165.jpg
 
I think Marco was trying to say that it's because of the HVX's lens. Adapter manufacturers are now working on camera specific Achromats (at least Wayne from SGpro camp and the Le Brothers from Letus are as far as I know) that'll help with edge to edge.

Remember, the camera wasn't made to take 35mm adapters.

Have you tried the edge focus thing yet?
 
Kholi said:
I think Marco was trying to say that it's because of the HVX's lens. Adapter manufacturers are now working on camera specific Achromats (at least Wayne from SGpro camp and the Le Brothers from Letus are as far as I know) that'll help with edge to edge.

Remember, the camera wasn't made to take 35mm adapters.

Have you tried the edge focus thing yet?
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Gotcha. I'm going to print that chart off in a minute and am going to test it tonight.
 
You got a shelf of DVDs or a poster?

Slap on your fastest lens (50mm 1.4 is mines), center up on the shelf or the Poster, plug your cam into a large monitor, TV, etc and check your edges.

Then slowly roll the focal ring until the sides are more in focus and even with the center.

You can use the chart, but if you don't have it this is a good way to check as there's still detail in the image to judge.

Actually, do it with a wider lens. I haven't tries this yet myself but it should help with the gamut.
 
Looking at your picture you don't have the spacers in the right place. It needs to go in this order:

RIGHT WAY
HVX > Achromat > Spacer(s) > Brevis

WRONG WAY
HVX > Spacer(s) > Achromat > Brevis


Try that and let us know if it works. You should get much better edge to edge now.


Marco
 
The spacers are in the wrong place as I mentioned, but the reason you need spacers is that they help the HVX focus to the ground glass in a more even manner. This is the same with the Redrock or SGpro. The Redrock is sharper with a spacer and the SGpro even includes a long spacer tube.


Marco
 
The Redrock + Spacer? Never heard of it. Maybe something I didn't know while I owned it.

I have heard of Hardmounting. The Spacer on the Brevis looks like it's adding space between the unit and the camera.

The Redrock's ring setup is a hardmount. The Brevis is supposed to be hardmounted from the get go, correct? So what's the need for spacers?

I asked Dennis this (as I often don't get questions answered by Dennis =P), but I thought the Brevis achromat may have been too close to the lens? I'm probably not accurate about that.

Hardmounting and Spacer: Two different things.
 
Avenger007 said:
Why were spacers added?
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To try and correct the problem... it didn't help. I'll switch it around and see if it does anything. Cinevate doesn't really promote using a spacer on the HVX, but I've seen several people that have so I thought it was worth a shot.
 
I'll switch it around and see if it does anything. Cinevate doesn't really promote using a spacer on the HVX, but I've seen several people that have so I thought it was worth a shot.
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It will do something. It will fix the problem. :)


Marco
 
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Alright, after a quick test it seems as though the flipping of the achromat and spacers, combined with Lenny's focus trick has corrected the problem, atleast to some degree. I'm now running settings of 72 zoom with 17 MF for more edge to edge sharpness, and 72 zoom 16MF for perfect center sharpness. I'll keep everyone posted.
 
Hey guys. Just wanted to say thanks for bringing the center focus/edge focus issue up. I would always just focus on the center of my Brevis GG and last night I found a compromise between center and edge sharpness that I can live with for now.

Thanks.
 
Lenny's owed a lot of credit for that. I've been doing it ever since with my Letus and with the super wides and my crappy glass it really helps.
 
I dont lock down either. I kinda just add it in to that run-down you do before you hit record. Brevis on? Zoom correct? Focus right? ok, now record. For me MF09 and Z77 (on hvx) are reliable enough in many cases, but slight adjustments to the focus ring (within the MF09) range are sometimes needed.

I need to work on compromising that center focus for the overall image. Its habit to go tack sharp on the center and then I'm like "aww..." in post when i get a good look at my wides. Thanks for the ongoing testing and posting of your findings that you guys do.
 
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