Sony confirms backfocus problem

Eric Pascarelli · April 27th, 2008, 12:07 PM

Zachary,

All pro lenses go past infinity by a bit.

The infinity mark should be infinity, not the lens stop position.

This is not indicative of the backfocus problem.

If you have to roll your focus to significantly less than infinity at wide angles to improve the focus of distant objects, then that's the backfocus problem.

For example, some have said that their best wide angle focus for distant objects appears when the lens is focused at 3 feet.

On my camera, despite several careful backfocus adjustments, I have to bring my focus to the 15' mark or a bit less for the best focus of distant objects when fully wide. I would call mine a mild backfocus problem.

Zachary Fink · April 27th, 2008, 12:26 PM

Thanks Eric - I thought as much, but I was surprised that my infinity focus is best a few mm on the close focus side of the dial of the actual infinity mark. I'm testing the BF outside, and am having difficulty discerning if I have the problem or not. I'm guessing that's because I don't - even though my firmware is v1.02. Worth sending it into Sony for an upgrade if I have a few weeks before my next shoot?

Eric Pascarelli · April 27th, 2008, 12:42 PM

Yours sounds like it's the same as mine. I will send mine in eventually, but in the mean time, I just cheat the focus closer when I'm doing wide shots.

I'm waiting until July or so when the new firmware comes out for the EX1 - it is rumored that we will be able to install it ourselves. I also have 1.02 but unlike many with the classic backfocus problem, my focusing is the same with all ND settings.

Matt Davis · April 27th, 2008, 05:00 PM

Quote:

Originally Posted by Eric Pascarelli

I just cheat the focus closer when I'm doing wide shots.

Just had a little 'ah-ha' moment...

There's a thing called the 'hyperfocal distance', which means, given the apature of a lens at a given focal length, is the optimal focus setting to get acceptable focus from infinity to something close up.

So if you take a PD150 zoomed out to the widest it will go, dial in F4, set focus to about 2 meters, infinity to about a meter and a half is going to be in focus. According to Christina Fox @ Urban Fox (purveyors of fine training to the BBC):

http://www.urbanfox.tv/workbooks/sonyz1/z1focus.htm

The Z1 is better - set at 1 meter, but she doesn't mention the F4 bit.

Anyway... IIRC, an attempt at hyperfocal distance didn't work for me before I did the 12-chart test. And even then I fluffed it because I didn't take into consideration the 1/2" chips effect.

Does the FB issue put infinity just outside of reach of the end stop, or a little bit before it? I felt that it was always a bit beyond the end stop which is why I never could get it.

Eric Pascarelli · April 27th, 2008, 05:09 PM

Still, distant objects should be sharper (or just as sharp) at infinity than at hyperfocal.

My experience on the EX1 is that the world gets softer at infinity than it is at a closer setting - so I use the closer setting.

Most other posts that I have read say that focus for distant objects gets sharper at closer settings, so it ca be said that infinity in before the end stop, not past it.

Tom Roper · June 25th, 2008, 09:14 AM

My camera shipped with the 1.05 firmware and has the non-parfocal behavior. It does not have the problem of different backfocus for different ND settings.

I don't understand how firmware is expected to solve the non-parfocal behavior in a mechanical lens design. This makes me skeptical. The exception would be if one of the focal elements is servo controlled even while in full manual.

If firmware was used to compensate for a fundamentally non-parfocal mechanical lens by adjusting the position of a servo controlled backfocus element within the group, it would be because the mechanically linked focus element is out of position.

I'm hesitant to perform the back flange procedure. My camera is pin sharp.

Although it would be extremely convenient to zoom in on the subject, focus and zoom out, Sony has provided effective tools for acquiring focus at wide angles, vis-a-vis the peaking controls which are the best I've seen.

The peaking has 3 color choices, but more importantly by choosing low, mid or high you can choose how much peaking to overlay the scene.

I found that by setting the iris to f1.9 and turning on the peaking, I can manually focus distant, featureless landscapes at wide angles, and observe the broader effect on the overall frame, near objects as well, by painting the image with yellow peaking. It's more trouble, but it's more effective for accurately getting all the desired subjects within the frame in focus than arbitrarily choosing one object in a parfocal method (even if it worked, which I'm not convinced it will.)

The expanded focus also works well, for getting a subject's face in focus from a wide angle, without first zooming in manually.

The improvement Sony could give us in a firmware update, would be to enable peaking and expanded focus at the same time.

I know there are strong opinions counter to this. I'm just giving you mine. I don't completely trust zooming in for focus, and then zooming back out even on lenses that are known to be parfocal, which in the case of EX1 Fujinon, there's reason for some doubt.

Piotr Wozniacki · June 25th, 2008, 10:21 AM

Quote:

Originally Posted by Tom Roper

I don't understand how firmware is expected to solve the non-parfocal behavior in a mechanical lens design. This makes me skeptical. The exception would be if one of the focal elements is servo controlled even while in full manual.

And indeed it is, Tom - the EX1's lens is never fully "mechanical", AFAIK.

Also, Wikipedia says (http://en.wikipedia.org/wiki/Parfocal_lens):

"Many so-called "zoom" lenses, particularly in the case of fixed lens cameras, are actually varifocal lenses, which gives lens designers more flexibility in optical design trade-offs (focal length range, maximum aperture, size, weight, cost) than parfocal zoom, and which is practical because of auto-focus, and because the camera processor can automatically adjust the lens to keep it in focus while changing focal length ("zooming") making operation essentially the same as a parfocal zoom"

I have bolded out the fragment, which confirms it can be done by the electronics (with a little help of some servo, of course).

But if you say your camera is pin sharp, I wouldn't adjust anything, either. And you're absolutely right that while the expanded focus feature is great, it would be even more useful with peaking on!

Serena Steuart · June 26th, 2008, 12:14 AM

Quote:

Originally Posted by Matt Daviss

Just had a little 'ah-ha' moment...

There's a thing called the 'hyperfocal distance', which means, given the apature of a lens at a given focal length, is the optimal focus setting to get acceptable focus from infinity to something close up.

Purely for the record: the hyperfocal distance represents a special case of depth of field in which objects at infinity, as well as near, are of acceptable sharpness. If the lens is focused at the hyperfocal distance, all image points between one-half that distance and infinity will not exceed a specific diameter of circle of confusion (i.e. acceptably sharp). That's how a fixed lens (non-focusing) camera is set up.
That distance (H) is determined by focal length squared divided by the product of f/stop and dia of circle of confusion. So the higher the f/stop, the shorter is H. As you know, H is a variable in DOF calculations.

Steven Thomas · July 1st, 2008, 02:58 PM

One thing for sure...

I'm finding the auto back focus feature on the EX1 to be very sensitive. I have the latest software 1.05 and regardless of ND on or OFF it can be a pain to get it set correctly. Also, I've seen nothing on my camera that shows I need to run the back focus on all ND filter conditions.

I've heard some say you can set it up at 3 meters away, and others mention more than 4 meters.

On mine, it seems to work best if you're over 4-5 meters away.
Also, the target must be larger and of course on the same plane with nothing else in the field of view when wide.

Honestly, I really WISH Sony would offer the FB (Flange Back) back focus adjustment with manual assistance control. This would allow accurate back focus settings.
This would be one featue I'd like to see implemented in the upcoming software release.

Peter Rixner · July 12th, 2008, 04:03 PM

Hello :)

This is my first post as a EX1 owner and after reading the entire thread, one of the first thing to do was to set the back focus with the described procedure.
Of course I checked it before and it was definetly off.

So: setup Siemans Star on the wall, clearded the obstacles in the room and EXECUTE.

Only one time executed and it's perfectly in focus now over the entire range. Nice :)

Before and after this, there was and is no difference between no, 1st and 2nd ND.
Which make sense to me as it's mechanically brought into the way as one can clearly hear by swithing it to the different positions.

Thanks!

I guess I have several posts here in the near future, now exploring all the functions of this beautiful camera :)

Peter

Tom Roper · July 13th, 2008, 04:58 PM

So do the numbers on the focus scale match the distance to a far away target when the zoom is wide?

Manu Pinto · June 13th, 2010, 09:28 AM

I've same issue, on my ex1 after focused on a obect and pull back the zoom everything is blurred. only with ND1 and ND2.
can I do the fix procedure only for ND? without ND focus is perfect...
I saw the video on Vimeo by Paul Kellett and I realized that the fix is very simple, but what are the conditions? (Distance, light)

Firmware 1.11

Edit:

Procedure ok and ex1 works fine
__________________________________________________
CameraStylo Film | SHOWREEL

Dominik Krol · November 17th, 2010, 12:42 PM

On my ex1 the backfocus can never be achieved perfectly.

When zoomed out, I will always get a sharper image when I turn the focus ring to Infinite distance. Especially on objects closer to the lens, I can see the sharpness gain when focusing far.

The problem only occurs when zoomed compleetelly out. Just a little zoon in, makes the image much sharper, and at the correct distance focus.

The auto BF dosent fix the problem, alltho it seems to do it... Right after the OK confirmation, the image is as sharp as it can be.. Then after 5 seconds when the focus wheel reclaims control, the image goes slight out of focus. When "MF assist" is enabled, I get reconfirmed that something is wrong.

I focus on an object 3 feet away. Zoom out, enable MF assist, and the focus turns all way to infinite. Image becomes sharper.

The things I mention here are subtle, and you can probalby only see the defocus on a good and large monitor, while focusing on the starchart.

However ever since I bought the camera (used) I had the feeling that the zoomed out image was softer than it's used to be on the rental ex1's I used before.

June 13th, 2010, 09:28 AM	#132
Manu Pinto New Boot Join Date: Oct 2005 Posts: 14	Is it possible? I've same issue, on my ex1 after focused on a obect and pull back the zoom everything is blurred. only with ND1 and ND2. can I do the fix procedure only for ND? without ND focus is perfect... I saw the video on Vimeo by Paul Kellett and I realized that the fix is very simple, but what are the conditions? (Distance, light) Firmware 1.11 Edit: EX1 back focus demo on Vimeo Procedure ok and ex1 works fine __________________________________________________ CameraStylo Film \| SHOWREEL Last edited by Manu Pinto; June 14th, 2010 at 09:06 AM.

April 27th, 2008, 12:07 PM	#121
Eric Pascarelli Major Player Join Date: Nov 2007 Location: Los Angeles, CA Posts: 498	Zachary, All pro lenses go past infinity by a bit. The infinity mark should be infinity, not the lens stop position. This is not indicative of the backfocus problem. If you have to roll your focus to significantly less than infinity at wide angles to improve the focus of distant objects, then that's the backfocus problem. For example, some have said that their best wide angle focus for distant objects appears when the lens is focused at 3 feet. On my camera, despite several careful backfocus adjustments, I have to bring my focus to the 15' mark or a bit less for the best focus of distant objects when fully wide. I would call mine a mild backfocus problem.

April 27th, 2008, 12:26 PM	#122
Zachary Fink Regular Crew Join Date: Feb 2005 Location: San Francisco, CA Posts: 134	Thanks Eric - I thought as much, but I was surprised that my infinity focus is best a few mm on the close focus side of the dial of the actual infinity mark. I'm testing the BF outside, and am having difficulty discerning if I have the problem or not. I'm guessing that's because I don't - even though my firmware is v1.02. Worth sending it into Sony for an upgrade if I have a few weeks before my next shoot?

April 27th, 2008, 12:42 PM	#123
Eric Pascarelli Major Player Join Date: Nov 2007 Location: Los Angeles, CA Posts: 498	Yours sounds like it's the same as mine. I will send mine in eventually, but in the mean time, I just cheat the focus closer when I'm doing wide shots. I'm waiting until July or so when the new firmware comes out for the EX1 - it is rumored that we will be able to install it ourselves. I also have 1.02 but unlike many with the classic backfocus problem, my focusing is the same with all ND settings.

April 27th, 2008, 05:09 PM	#125
Eric Pascarelli Major Player Join Date: Nov 2007 Location: Los Angeles, CA Posts: 498	Still, distant objects should be sharper (or just as sharp) at infinity than at hyperfocal. My experience on the EX1 is that the world gets softer at infinity than it is at a closer setting - so I use the closer setting. Most other posts that I have read say that focus for distant objects gets sharper at closer settings, so it ca be said that infinity in before the end stop, not past it.

June 25th, 2008, 09:14 AM	#126
Tom Roper Trustee Join Date: Jun 2004 Location: Denver, Colorado Posts: 1,891	My camera shipped with the 1.05 firmware and has the non-parfocal behavior. It does not have the problem of different backfocus for different ND settings. I don't understand how firmware is expected to solve the non-parfocal behavior in a mechanical lens design. This makes me skeptical. The exception would be if one of the focal elements is servo controlled even while in full manual. If firmware was used to compensate for a fundamentally non-parfocal mechanical lens by adjusting the position of a servo controlled backfocus element within the group, it would be because the mechanically linked focus element is out of position. I'm hesitant to perform the back flange procedure. My camera is pin sharp. Although it would be extremely convenient to zoom in on the subject, focus and zoom out, Sony has provided effective tools for acquiring focus at wide angles, vis-a-vis the peaking controls which are the best I've seen. The peaking has 3 color choices, but more importantly by choosing low, mid or high you can choose how much peaking to overlay the scene. I found that by setting the iris to f1.9 and turning on the peaking, I can manually focus distant, featureless landscapes at wide angles, and observe the broader effect on the overall frame, near objects as well, by painting the image with yellow peaking. It's more trouble, but it's more effective for accurately getting all the desired subjects within the frame in focus than arbitrarily choosing one object in a parfocal method (even if it worked, which I'm not convinced it will.) The expanded focus also works well, for getting a subject's face in focus from a wide angle, without first zooming in manually. The improvement Sony could give us in a firmware update, would be to enable peaking and expanded focus at the same time. I know there are strong opinions counter to this. I'm just giving you mine. I don't completely trust zooming in for focus, and then zooming back out even on lenses that are known to be parfocal, which in the case of EX1 Fujinon, there's reason for some doubt.

July 1st, 2008, 02:58 PM	#129
Steven Thomas Trustee Join Date: Sep 2005 Location: Gilbert, AZ Posts: 1,896	One thing for sure... I'm finding the auto back focus feature on the EX1 to be very sensitive. I have the latest software 1.05 and regardless of ND on or OFF it can be a pain to get it set correctly. Also, I've seen nothing on my camera that shows I need to run the back focus on all ND filter conditions. I've heard some say you can set it up at 3 meters away, and others mention more than 4 meters. On mine, it seems to work best if you're over 4-5 meters away. Also, the target must be larger and of course on the same plane with nothing else in the field of view when wide. Honestly, I really WISH Sony would offer the FB (Flange Back) back focus adjustment with manual assistance control. This would allow accurate back focus settings. This would be one featue I'd like to see implemented in the upcoming software release.

July 12th, 2008, 04:03 PM	#130
Peter Rixner Regular Crew Join Date: Mar 2005 Location: near Munich, Bavaria Posts: 139	Hello :) This is my first post as a EX1 owner and after reading the entire thread, one of the first thing to do was to set the back focus with the described procedure. Of course I checked it before and it was definetly off. So: setup Siemans Star on the wall, clearded the obstacles in the room and EXECUTE. Only one time executed and it's perfectly in focus now over the entire range. Nice :) Before and after this, there was and is no difference between no, 1st and 2nd ND. Which make sense to me as it's mechanically brought into the way as one can clearly hear by swithing it to the different positions. Thanks! I guess I have several posts here in the near future, now exploring all the functions of this beautiful camera :) Peter

July 13th, 2008, 04:58 PM	#131
Tom Roper Trustee Join Date: Jun 2004 Location: Denver, Colorado Posts: 1,891	So do the numbers on the focus scale match the distance to a far away target when the zoom is wide?

November 17th, 2010, 12:42 PM	#133
Dominik Krol Regular Crew Join Date: Oct 2010 Location: Copenhagen Denmark Posts: 70	On my ex1 the backfocus can never be achieved perfectly. When zoomed out, I will always get a sharper image when I turn the focus ring to Infinite distance. Especially on objects closer to the lens, I can see the sharpness gain when focusing far. The problem only occurs when zoomed compleetelly out. Just a little zoon in, makes the image much sharper, and at the correct distance focus. The auto BF dosent fix the problem, alltho it seems to do it... Right after the OK confirmation, the image is as sharp as it can be.. Then after 5 seconds when the focus wheel reclaims control, the image goes slight out of focus. When "MF assist" is enabled, I get reconfirmed that something is wrong. I focus on an object 3 feet away. Zoom out, enable MF assist, and the focus turns all way to infinite. Image becomes sharper. The things I mention here are subtle, and you can probalby only see the defocus on a good and large monitor, while focusing on the starchart. However ever since I bought the camera (used) I had the feeling that the zoomed out image was softer than it's used to be on the rental ex1's I used before.