My STILL ongoing journey of achieving M2 Edge to Edge sharpness

S

sotty

Active member
Sample shots-

http://www.dvxuser.com/V6/showthread.php?t=79948


I had the M2 for 45 days. I have been adjusting and tweaking for 10-20 hours a week. I use the Marshall monitor, a Sony 32” HDTV and a Sony 60” HDTV. I have several lens,
Nikon’s and Zeiss and have use every combination of F-stop there is on both the lens and camera.

Bottom line is I never could achieve edge to edge sharpness, with the left side somewhat sharper than the right. That the left is sharper than the right it still wasn't dead center sharp, and for that matter I was never able to achieve isolated edge sharpness at all. So after 200 hours of adjusting every which way imaginable, reading the support forums, watching the online video steps, and still not getting edge sharpness, it dawned on me, it’s not a problem with the image element or lens or settings but the HD Achromatic lens and maybe more so of the relationship with “my” HVX200. On my HXV with only the HD Achromatic lens attached and using the 82mm to 72mm step down ring you would think after screwing it in that it would be almost near perfect, left/right, up/down alignment, but its not. On my HVX the right side is favored more, considerably more. Being the left edge drops off the screen before the right edge. At Z37 the left side is off the screen but I have to zoom in until Z55 before the right side falls off. Again, there is nothing to adjust, the HD Achromatic lens gets screwed in, hard mounted right to the front of the HVX lens via the 82mm to 72mm step down. There is no cross-threading involved and I duplicate this 30+ times of unscrewing everything and putting back together and back on the HVX. That’s problem #1. The next problem is that no matter what setting I use, it's impossible for me to get edge sharpness period, whether the center was out of focus or not, and with only having the HD Achromatic lens attached.

My tests and therapy;

I unscrewed the HD Achromatic, stabilized it with a custom rig where I could move the HD Achromatic up/down, left/right, in/out in extreme small movements in millimeters.

I flattened a piece of sandpaper to a box and placed it 4” in front of the HD Achromatic and lit it with a 500 watt light. At this close range you can really see the surface of the sandpaper.

When moving the center of the HD Achromatic to the edge of the HVX lens the edges start to shapen. Edge on edge, its soft.

Keep in mind, vertically, top/bottom of image was always sharp, it’s the left/right edge that wasn’t. Oddly enough this leads me to believe that there is slight right/left distortion with the relationship between the HVX lens and the HD Achromatic lens and is not one that’s 100% pure. Based on my test I'd say more like 95%. I applaud those that have achieved edge to center to edge sharpness as I believe it is more a stoke of luck of having pure equipment than that of minute tweaking. So for me it comes down to tolerance. Do I live with the soft edges or shoot without the M2. Or order another HD Achromatic lens to see if there is a defect and/or order another HVX200.

But here is the kicker, my DP has the exact same setup, HVX and M2. And low and behold we achieved the exact same results.

This is simply my ongoing journey of obtaining edge to edge sharpness, for what its worth and understand why some of you are pulling your hair out…for those that still have hair…...until then.
 
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If you can, post a clip or two of some real world shots, I'd like to see how "soft" is soft, in regard to what you are finding.

Thanks for posting.
Pete.
 
Only thing that comes to mind is if you were using say a Nikon 50mm f/1.4, full open, there is known softening on the edge, as highlighted by Ken Rockwell. Upon re-reading your thread, I now realise you mentioned trying all f-stop combo's, etc. Sorry to hear you have spent so much time trying to get satisfactory images. What have the chaps at RR said in response? I would be interested to hear how this story ends.
 
sotty,
Its a little hard to diagnose this from your post, but a number of thoughts come to mind.

I can't imagine the achromat is at fault unless it is very wacko so it sounds like you are playing with the wrong element.

I see 3 possible problems

1 - You may not be looking dead-on centered at the target area of the ground glass in the M2. This would explain one side being closer than the other and also explain why the motor doesn't seem to be centered.

Is the motor centered? - you didn't mention. If its not you could be looking at it from slightly to one side. This would make one side focus closer than the other.
One way to test this is to get the adapters to make a "hard mount " connection (mainly a 55mm M-M & a 72-55 step down adapter) then screw the whole thing together. This will absolutely center the M2 on the HVX.

Working backwards you can then loosen the allen screws on the camera plate and slide the M2 onto the rails. Then adjust the allen screws so that when they're tight the M2 will stay aligned with the M2.

2. This should eliminate side to side focus differences unless there is a problem in the manufacture of the M2.

3. The next thing to see is if you are centered on the motor- both up and down and side to side. Mine wasn't and though its easy to lower or raise the motor, there is no side to side adjustment.
What i did was lower one screw on the motor mt so it shifted the ground glass a bit to the side. This allowed me to get left and right side to leave the frame at the same Zoom #.

4. This took a long time to figure out as this process wasn't exactly posted, but once set it has been very easy to repeat in practice.

5. the other issue is that the precise distance of achromat to M2 is critical for getting corners and center to focus at the same point.
I found that the hard mt distance was wrong for our rig.
What i do - is have a 55mm M-M adapter ring on the M2 then a 55-72 step down adapter. (I can't remeber if there is another 55mm spinning ring in there, but i think we removed it). I slide the 72mm step down ring until it just snugs into the threads of the achromat, but i don't screw it in. This seems like pretty much the right distance.

I'vee never gotten real corner to center focus perfect, the corners are always softer, but its not bad and its always even.

Good luck, let me know if this helps.

Lenny Levy
 
Thanks Lenny for the valuable info. I use different (hired) rigs all the time, to date I've been lucky. Hopefully I won't need this stuff...but you never know.

Pete.
 
Thanks for the reply. I will try and get some footage up. Lenny, yes, everything is dead center. I have everything hardmounted and I tried without being hardmounted. I adjusted the motor up/down, the ground glass in/out.

I experimented with every distance, achromat to HVX, achromat to m2. I use gauges to check everything is dead on. Left/right falloff is perfect.

Again the problem is just getting edge sharpness at all. I'm trying to at least get isolated edge sharpness, not worrying about the center. I just can't understand why the edges of the ground glass (image element) won't focus.

I may be making to much of it as I see many, including yourself that have soft edges. But I see other samples with very sharp edges.
 
I don't understand, if you are dead center why does one side go off the edge of the zoom before the other?

I'm confused also by your statement earlier that left and right seem to focus at different points - that indicates a serious problem.

If it is just corner to center sharpness, I agree it is not perfect. i assume it is the nature of the beast though I've been meaning to send a chart pdf to Brian at redrock for his opinion.

Maybe we should all post those. That might be interesting as we don't have a clear idea of how good this should get.

I made big blow-ups of resolution charts - 4' and 3' and always use those when setting up the M2 .

- Lenny Levy
 
The image element and motor is dead center. What I'm referring to when I say one side falls off before the other is the Achromatic lens. If you view with just the Achromatic lens attached you can see the edge when you zoom out. Now zoom in and I have the left side falling off before the right. Z37 the left edge of the Achromatic lens is off the screen but I have to zoom in until Z55 before the right falls off.

I find this very odd as it is hard mounted with the step down ring.

The edge softness with all attached is another story.
Redrock is sending me another image element, but I don't think this is the problem.
 
Hmm I don't have mine in the house right now so I can't compare. sounds pretty weird though. Maybe it is a bad achromat
 
I think its the achromat or the other glass inside the adapter.
Who knows where the glass comes from... it is the weakest link in the optical chain.

I'd bet if the M2 glass was from Zeiss or Shneider or Panavision, the image would be in focus edge to edge.

The M2 does what it does for a decent price and I don't expect perfection from it.
 
HVX200+Redrock M2+Zeiss 85mm. No color correction.
Here's some screen grab samples. Using Zeiss 85mm. Cloudy day.

baby.jpg



The head on pillow was inside, using a $9.00 500w work light from Walmart.
Zeiss 50mm.

head-pillow.jpg



Outside, cloudy day, Zeiss 50mm. Text to show edge softness.

box.jpg



Outside, night, using $9 500w work light. Zeiss 50mm.

pink-flower.jpg
 
I'm sure you've checked this, but my ACHROMAT had the GLASS in backwards, resulting in the problems you've described. Redrock confirmed that some of the lenses were mounted backwards. You'll need a filter wrench to take the Achromat apart and reverse the lens.

Hope this helps...
 
How much light loss are you dealing with? The 'head on pillow' shot looks a lil dark for something with 500w splashed on it.
 
>but my ACHROMAT had the GLASS in backwards

I was actually was thinking of this and did check. It would be a stretch I thought but you said you had this problem. So I will revisit this again.

>How much light loss are you dealing with?

I'd say a full stop.
 
how did you know it was in backwards? hard to believe.



brm said:
I'm sure you've checked this, but my ACHROMAT had the GLASS in backwards, resulting in the problems you've described. Redrock confirmed that some of the lenses were mounted backwards. You'll need a filter wrench to take the Achromat apart and reverse the lens.

Hope this helps...
Click to expand...
 
Hi Sotty. Looking at just the first shot, "Using Zeiss 85mm. Cloudy day."... what aperture was the Zeiss and the HVX set to? How were you monitoring focus? What is it about the shot that don't like?

On the text shot, what were the settings and how close were you to the object? Tripod? The object looks slightly curved, is that correct?

Pete.
 
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The settings were always on 5.6 on the camera and 5.6 on the Zeiss. The text shot was 3'10" away. Using the marshall 7" monitor outside and a Sony HDTV for inside. I'm a focus nut so I know it was best I could get. Everything appears to soft to me, thats what I don't like. I'm shooting a feature in Feb on a $100k budget. I can't afford to have a soft image.


The box was tilted but not curved and if it was only by a millimeter. The hvx without the m2 at same distance and focal length is very sharp. It shouldn’t be that poor of a downgrade when adding M2/Zeiss.

I believe its the image element. I think its distorted. Redrock is sending me another. Interesting I can flip the element and have the shiny side outwards and get better results. So I will assume redrock sent me the M2 setup properly.
 
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Sotty,
Do you have a blow up from a resolution chart.
If not, download one from the web ( I think there's one on the Redrock forum somewhere.) I could prob email you one.

Anyway - go to Kinko's, blow it up to 4' wide and use that to test these issues. I can't tell anything from those stills
A res chart is essential for me. It goes with me to every shoot.

Also, I would pull that glass filter out of the Redrock . What is it there for? buy a lens cap instead.
 
You MUST be hard mounted to get accurate results. The 72mm achromat is better than the 55mm original version.

Here's a chart I shot with a 17-35mm 2.8 lens at F4.
http://www.steveshovlar.com/chart.tif
Right mouse click and "save target as".

I have found using Nikons wide open is not the way to go. Try F4 or 5.6 if you have enough light. Wide open leads to sofer edges, and its the Nikons rather than the M2.
 
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