Vignette problem

Gerald Loidl · March 7th, 2008, 11:56 AM

Quote:

Originally Posted by Dustin Carpio

I must have gotten lucky. I haven't experienced any of the problems that so many have had on this thread and my camera was bought in January. I do see a tiny vignette in some of my footage, but nothing that's noticeable and it seems to be only at certain zoom lengths. I've been trying to get my camera to show the problems I hear about on this forum, but beyond the small vignette in the upper left hand corner at some zoom lengths, it's fine.

Hopefully Sony will honor the warranties longer then 90 days, because cameras with focus and vignette problems are lemons.

Dustin,
when reading your description you do have the typical vignetting issue if you allready notice it in your footage. Its only there at certain zoom lengths - thats the typical symptom. Most of us only have it in certain corners. There are cameras out there which do not show any vignetting at all - and there shouldn´t be any. So I would not say that yours is problem free... ;-)

Dustin Carpio · March 7th, 2008, 01:41 PM

Quote:

Originally Posted by Gerald Loidl

Dustin,
when reading your description you do have the typical vignetting issue if you allready notice it in your footage. Its only there at certain zoom lengths - thats the typical symptom. Most of us only have it in certain corners. There are cameras out there which do not show any vignetting at all - and there shouldn´t be any. So I would not say that yours is problem free... ;-)

You're correct, it is a problem. But when I look at frame grabs people have shown on here mine is a lot less noticeable. You really have to look to see it and then it's just barely there. I'm not happy that it's there, but it's not a huge deal breaker for me.

I'm taking it to the Grand Canyon on a tech scout all this week. So, I'll have plenty of time to really work the camera out. If it's visible at all I should be able to see it and exaggerate the vignette in the very bright canyon scenery.

Gerald Loidl · March 11th, 2008, 05:59 AM

my camera came back from service yesterday. The vignette is gone - but it still has a back focus problem with ND on...

Florian von Westerholt · March 11th, 2008, 08:33 AM

Gerald, did you read, what the German guys have done here:
http://www.videotreffpunkt.com/threa...user=0&page=56
In the Service menu you find the option "auto fb adjust". But maybe you loose your warranty by using this option.

Lonnie Bell · March 11th, 2008, 08:36 AM

Florian,
did they fix your backfocus issue?

Gerald Loidl · March 11th, 2008, 08:38 AM

Hi Florian,
I´ve tried this procedure about 20 times with some success.
I think I could fix it by 90%, but there is still a difference between ND and no ND. I did a splitscreen video and can clearly see the difference between the filters. It´s much better than before but still not acceptable for me.

thanks,
Gerald

Florian von Westerholt · March 11th, 2008, 09:07 AM

Quote:

Originally Posted by Lonnie Bell

Florian,
did they fix your backfocus issue?

They fixed it, yes. I made a detailed test with a technician. But I need some further tests and some work with the cam for a few days so I can really say, its all o.k. No time for the moment, will last til April, my first real docu-shot with the ex 1 will just start in May. So im not pressed for time.

BTW: I love this machine, the workflow, the pictures, the possibilities, great advance for my work.

Michael H. Stevens · March 11th, 2008, 10:42 AM

How can an ND filter effect back focus?

Eric Pascarelli · March 11th, 2008, 11:18 AM

Putting any filter in the optical path behind the lens will affect back focus because the glass has a different refraction index from the air that it replaces. It will make the lens focus farther back by about 1/3 the thickness of the glass (if I remember correctly). That's a huge distance when speaking of the tolerances of back focus on a 1/2" chip.

That said, I don't know exactly why it affects the EX1. Cameras usually have a clear "comp" filter that goes in the place of the ND so that the light travels through the same amount of glass in all filter settings. Even the EX1 reads "ND: Clear" on the LCD display when you switch the ND filtering to "Off."

My theory, as stated earlier in this thread, is that the EX1 has no clear filter inside but instead relies on a servo driven compensation for the absent ND filter and that in some cameras, this compensation is incorrectly calibrated or not working for whatever reason.

Just a theory but I can't think of another reason why back focus would change with the filter settings. Unless the internal filters themselves are the wrong thickness or something bizarre like that?

Bill Ravens · March 11th, 2008, 11:31 AM

The only way a zero power, planar piece of glass could affect focal point is if the glass was mounted at a angle relative to the mean light path. I doubt that Sony is building powered ND filters.

Eric Pascarelli · March 11th, 2008, 11:51 AM

Bill - not true.

Glass (versus no glass) will extend the back focus. The rays will still converge at the same angle when exiting the glass as when entering (because the faces of the glass are parallel), but they adopt a shallower angle when "inside" the glass, thereby extending (or pushing backward) the back focus.

This shallower angle inside the glass makes the effect equal to about 1/3 the thickness of the glass.

Bill Ravens · March 11th, 2008, 12:25 PM

Eric,
You are right if the incoming light rays are convergent. What I said is true when the incoming rays are collimated. Do you think Fujinon optical engineers are dumb enough to put the ND filters in a convergent beam? This would really be rather unwise. I'm not being argumentative, I really want to know. If they really DID do this, they'd be forced into having a powered optic, which would drive cost unrealisitically, and complicate alignment requirements.

Perhaps, since the ND filters come with the camera body, and the lens is an add-on, they incoming rays are, indeed, convergent. Holy jeez!! What a thought.

Eric Pascarelli · March 11th, 2008, 12:44 PM

Bill,

I would doubt that there is the luxury of a collimated beam anywhere in that lens in which to insert an ND. I am assuming that the filters are behind the optics (as is the case in interchangeable lens cameras and gel filtration on film cameras) and hence in a converging beam. There's no need for there to be a powered optic as long as its application is consistent with all filters (or compensated for) and accounted for in the design. In fact, the automatic back focus adjustment (which is purportedly LUT based) would take care of it automatically.

Anyway, there is no way I can conceive of for a filter to affect the backfocus unless it's doing what we see in that illustration. Don't you agree?

Would be nice to know what's going on inside that lens rather than speculating. The answers lie in the palms of our hands if we are willing to dissect our cameras to find out!

Bill Ravens · March 11th, 2008, 12:55 PM

Eric...yes, I quite agree. A clear piece of glass in place of an ND filter would be a cheap solution.
LOL...I'm not brave enough to try disassembly of my EX1.

Michael H. Stevens · March 11th, 2008, 04:28 PM

You are all forgetting this problem only effects one particula camera so it is not a design issue. My guess is that one of the ND filters has come loose. Definately a return to SONY and then let us all know what is happening.

March 11th, 2008, 08:36 AM	#590
Lonnie Bell Major Player Join Date: Mar 2006 Location: Las Vegas, NV United States Posts: 361	Florian, did they fix your backfocus issue? __________________ Lonnie Bell mamas boy productions Las Vegas, NV

March 11th, 2008, 11:51 AM	#596
Eric Pascarelli Major Player Join Date: Nov 2007 Location: Los Angeles, CA Posts: 498	Bill - not true. Glass (versus no glass) will extend the back focus. The rays will still converge at the same angle when exiting the glass as when entering (because the faces of the glass are parallel), but they adopt a shallower angle when "inside" the glass, thereby extending (or pushing backward) the back focus. This shallower angle inside the glass makes the effect equal to about 1/3 the thickness of the glass. Attached Images

March 11th, 2008, 05:59 AM	#588
Gerald Loidl Regular Crew Join Date: Feb 2008 Location: Austria Posts: 122	my camera came back from service yesterday. The vignette is gone - but it still has a back focus problem with ND on...

March 11th, 2008, 08:33 AM	#589
Florian von Westerholt New Boot Join Date: Mar 2008 Location: Kiel Germany Posts: 6	Gerald, did you read, what the German guys have done here: http://www.videotreffpunkt.com/threa...user=0&page=56 In the Service menu you find the option "auto fb adjust". But maybe you loose your warranty by using this option.

March 11th, 2008, 08:38 AM	#591
Gerald Loidl Regular Crew Join Date: Feb 2008 Location: Austria Posts: 122	Hi Florian, I´ve tried this procedure about 20 times with some success. I think I could fix it by 90%, but there is still a difference between ND and no ND. I did a splitscreen video and can clearly see the difference between the filters. It´s much better than before but still not acceptable for me. thanks, Gerald

March 11th, 2008, 10:42 AM	#593
Michael H. Stevens Major Player Join Date: Sep 2007 Location: Palm Desert, California Posts: 311	How can an ND filter effect back focus?

March 11th, 2008, 11:18 AM	#594
Eric Pascarelli Major Player Join Date: Nov 2007 Location: Los Angeles, CA Posts: 498	Putting any filter in the optical path behind the lens will affect back focus because the glass has a different refraction index from the air that it replaces. It will make the lens focus farther back by about 1/3 the thickness of the glass (if I remember correctly). That's a huge distance when speaking of the tolerances of back focus on a 1/2" chip. That said, I don't know exactly why it affects the EX1. Cameras usually have a clear "comp" filter that goes in the place of the ND so that the light travels through the same amount of glass in all filter settings. Even the EX1 reads "ND: Clear" on the LCD display when you switch the ND filtering to "Off." My theory, as stated earlier in this thread, is that the EX1 has no clear filter inside but instead relies on a servo driven compensation for the absent ND filter and that in some cameras, this compensation is incorrectly calibrated or not working for whatever reason. Just a theory but I can't think of another reason why back focus would change with the filter settings. Unless the internal filters themselves are the wrong thickness or something bizarre like that?

March 11th, 2008, 11:31 AM	#595
Bill Ravens Join Date: Nov 2001 Location: santa fe, nm Posts: 3,264 Images: 10	The only way a zero power, planar piece of glass could affect focal point is if the glass was mounted at a angle relative to the mean light path. I doubt that Sony is building powered ND filters.

March 11th, 2008, 12:25 PM	#597
Bill Ravens Join Date: Nov 2001 Location: santa fe, nm Posts: 3,264 Images: 10	Eric, You are right if the incoming light rays are convergent. What I said is true when the incoming rays are collimated. Do you think Fujinon optical engineers are dumb enough to put the ND filters in a convergent beam? This would really be rather unwise. I'm not being argumentative, I really want to know. If they really DID do this, they'd be forced into having a powered optic, which would drive cost unrealisitically, and complicate alignment requirements. Perhaps, since the ND filters come with the camera body, and the lens is an add-on, they incoming rays are, indeed, convergent. Holy jeez!! What a thought.

March 11th, 2008, 12:44 PM	#598
Eric Pascarelli Major Player Join Date: Nov 2007 Location: Los Angeles, CA Posts: 498	Bill, I would doubt that there is the luxury of a collimated beam anywhere in that lens in which to insert an ND. I am assuming that the filters are behind the optics (as is the case in interchangeable lens cameras and gel filtration on film cameras) and hence in a converging beam. There's no need for there to be a powered optic as long as its application is consistent with all filters (or compensated for) and accounted for in the design. In fact, the automatic back focus adjustment (which is purportedly LUT based) would take care of it automatically. Anyway, there is no way I can conceive of for a filter to affect the backfocus unless it's doing what we see in that illustration. Don't you agree? Would be nice to know what's going on inside that lens rather than speculating. The answers lie in the palms of our hands if we are willing to dissect our cameras to find out!

March 11th, 2008, 12:55 PM	#599
Bill Ravens Join Date: Nov 2001 Location: santa fe, nm Posts: 3,264 Images: 10	Eric...yes, I quite agree. A clear piece of glass in place of an ND filter would be a cheap solution. LOL...I'm not brave enough to try disassembly of my EX1.

March 11th, 2008, 04:28 PM	#600
Michael H. Stevens Major Player Join Date: Sep 2007 Location: Palm Desert, California Posts: 311	You are all forgetting this problem only effects one particula camera so it is not a design issue. My guess is that one of the ND filters has come loose. Definately a return to SONY and then let us all know what is happening.