Sharp center, soft everywhere else (Z280)

[David Anderson]

I just completed a shoot for a client and discovered the center of the image is sharp but it's soft and basically out of focus everywhere else. Anyone got any ideas?

Just bought the camera from LensRentals and it only had 310 hours on it.

https://f.io/St9zRFEv

I went from 2.8 to 8 and it made no difference. It is more noticeable on the right side of the frame but it's definitely noticeable on the left as well. Center is the only place that is sharp.

Any advice would be appreciated.

Thanks,

David

[Doug Jensen]

David, I can tell from the clip's metadata that you have the Macro switch turned on. Try another test with it turned off. I'm not sure if it will make a difference or not but you need try that before sending it in for repair or for a refund.

[David Anderson]

Doug - thanks,

That didn't do the trick. I can tell you there is a humming/buzzing coming from the lens area that almost sounds like a short circuit. If I move the ring back to the manual focus position the noise stops. This is when the camera is fixed in place and focused on a fixed object so it's not as if it is tracking and moving around.

I'll be calling lensrentals Monday and seeing what they have to say. They sold me this as an excellent condition camera.

Thanks again,

David

[Christopher Young]

Also, make sure you are not shooting much past F/5.6 to avoid diffraction which becomes more apparent as you resolve further from the center of the lens. The Z280 seems to prefer F/4.0 or wider to get the best out of its lens. I think Doug with his experience with the Z280 may attest to this as well.

The Z280 1/2" sensor is 6.4mm x 4.8mm. This means a diameter of = 8mm. On that basis, you have a 4096-pixel width sensor with photosites (pixels) of 1.56µm width.

As you can see from the accompanying images a sensor with the above specs or close to them will start to exhibit diffraction at F/5.6 and beyond. For a 4K 2/3" sensor you start to run into diffraction at around at just under F/8.0. For sports OB shoots 1st-grade stadiums have specifically mandated very even lighting requirements for TV coverage, The minimum lighting for those stadiums is set at a level where modern 2/3" cameras can shoot at F/8.0. Setting F/8.0 avoids diffraction and helps the close-up cameras work with as much DOF as possible for the fast-moving action. The CCU operator will set the cameras at F/8.0 and no more adjustments are made to the apertures unless a director calls a camera off the pitch lighting into a crowd shot or similar where the lighting is of a lower level.

I find with the 1/2" cams, especially the 4K ones if you can stay at F/5.6 or wider then generally you will get the best results. The Z280 if stopped down below F/8.0 can go quite soft. Especially in 4K at the longer end of the lens. But then this type of diffraction performance applies to any 1/2" chip camera. Like Sony's earlier version EX and PMW series 1/2" cameras.

Sensor calculations based on sensor dimensions in millimetres

https://www.vision-doctor.com/en/cam...sor-ratio.html


Diffraction limits

https://www.cambridgeincolour.com/tu...hotography.htm

Chris Young

[David Anderson]

Thanks for the info. Per Dougs advice my main shoot was at 2.8. The video link above was between 1.9 and 8 just to see if there was any difference (there was none).

There is something definitely wrong with the camera/lens. It should not be soft at all on the outside ends of the frame with people on the same plane.

https://f.io/AD-UVksJ

If you look in that photo the person sitting to the right is completely out of focus and even the person in the center is sharp in only parts of the shot. I couldn't get a 2 up shot of people because of this.

I'm hoping Lensrentals will do the right thing and take care of this. I bought this less than 30 days ago and have only used it on 2 shoots. The other shoot was of a single person and there was enough distance between them and the background that I didn't really pay attention to the outer sides of the frame figuring it was DOF causing the background to look OOF.

https://f.io/N2lmLodJ - You can see I purchased the one with "exceptional glass".

Thanks!

David

Originally Posted by Christopher Young

Also, make sure you are not shooting much past F/5.6 to avoid diffraction which becomes more apparent as you resolve further from the center of the lens. The Z280 seems to prefer F/4.0 or wider to get the best out of its lens. I think Doug with his experience with the Z280 may attest to this as well.

The Z280 1/2" sensor is 6.4mm x 4.8mm. This means a diameter of = 8mm. On that basis, you have a 4096-pixel width sensor with photosites (pixels) of 1.56µm width.

As you can see from the accompanying images a sensor with the above specs or close to them will start to exhibit diffraction at F/5.6 and beyond. For a 4K 2/3" sensor you start to run into diffraction at around at just under F/8.0. For sports OB shoots 1st-grade stadiums have specifically mandated very even lighting requirements for TV coverage, The minimum lighting for those stadiums is set at a level where modern 2/3" cameras can shoot at F/8.0. Setting F/8.0 avoids diffraction and helps the close-up cameras work with as much DOF as possible for the fast-moving action. The CCU operator will set the cameras at F/8.0 and no more adjustments are made to the apertures unless a director calls a camera off the pitch lighting into a crowd shot or similar where the lighting is of a lower level.

I find with the 1/2" cams, especially the 4K ones if you can stay at F/5.6 or wider then generally you will get the best results. The Z280 if stopped down below F/8.0 can go quite soft. Especially in 4K at the longer end of the lens. But then this type of diffraction performance applies to any 1/2" chip camera. Like Sony's earlier version EX and PMW series 1/2" cameras.

Sensor calculations based on sensor dimensions in millimetres

https://www.vision-doctor.com/en/cam...sor-ratio.html


Diffraction limits

https://www.cambridgeincolour.com/tu...hotography.htm

Chris Young

[David Anderson]

Just to add - here is an audio file of me with the camera on and moving between manual and auto focus and I'm not changing the zoom at all and it's a fixed subject. The focus is not moving but you can clearly hear some type of motor humming/buzzing sound.

https://f.io/tntobq0A

Thanks again!

David

[Doug Jensen]

Originally Posted by David Anderson

Doug - thanks, That didn't do the trick. I

Yeah, I didn't think it would fix the problem, but worth checking nonetheless. Hopefully LenRentals will stand behind it. I do know that LenRentals and Sony have some kind of official relationship because every time I get demo gear from Sony it come via LensRentals.

[Doug Jensen]

Originally Posted by Christopher Young

Also, make sure you are not shooting much past F/5.6 to avoid diffraction which becomes more apparent as you resolve further from the center of the lens. The Z280 seems to prefer F/4.0 or wider to get the best out of its lens. I think Doug with his experience with the Z280 may attest to this as well.

Yes, that is all true. I shoot 99% of everything with my Z280 at f/2.8, which is really easy to do thanks to the variable ND filter. About the only time I'll go smaller than that is in really strong brightlight and I've maxed out the internal ND and I don't have a ND filter handy to put on the lens.

I wish it was possible to map the iris ring on the lens to change the ND filter instead of the apergure. That way I could lock the lens at f/2.8 but still make my on-the-fly exposure changes with the iris ring. That would be a damn cool feature to put on a camera.

Here's a video I produced a few years ago to address diffraction and back-focus on the Z280.

YouTube (Short URL)

[Christopher Young]

Originally Posted by David Anderson

If you look in that photo the person sitting to the right is completely out of focus and even the person in the center is sharp in only parts of the shot. I couldn't get a 2 up shot of people because of this.

Yes, this is beginning to sound more like a centring/tilt issue with one or more of the lens elements. Time for it to be replaced. With camcorders, it's best to replace the whole lens assembly as a single unit not 'fix it'. I know a really good Sony factory-trained tech who says ever since the advent of the EX1 camcorders this is the only real way to fix lens-related issues with the one-piece camcorders. Good luck with Lensrentals. Roger Cicala has a good reputation so I think you should be fine.

Chris Young

[David Anderson]

Good to hear from you and Doug that Lensrentals is a stand up company. I'm hoping that will prove true tomorrow when I call them. I'm newer to the higher end of the videography market but have been in photography for 30 years. I've done all sorts of lens tests over the years and I understand what should and shouldn't look right.

I don't think I'm making a huge issue of something small, it's a huge issue and needs to be rectified. I can't deliver footage like that to my clients.

Thanks for all the input and encouragement.

Best,

David

Originally Posted by Christopher Young

Yes, this is beginning to sound more like a centring/tilt issue with one or more of the lens elements. Time for it to be replaced. With camcorders, it's best to replace the whole lens assembly as a single unit not 'fix it'. I know a really good Sony factory-trained tech who says ever since the advent of the EX1 camcorders this is the only real way to fix lens-related issues with the one-piece camcorders. Good luck with Lensrentals. Roger Cicala has a good reputation so I think you should be fine.

Chris Young

[David Anderson]

Well this is the best proof I have. About 30' from the subject - just a sign. It's obvious the picture is not sharp around the edges and I'm even beginning to question the center sharpness (It's not as tack sharp as I'd expect).

This was shot wide open.

https://f.io/EaoLlMu9

Wish me luck on my call with Lensrentals tomorrow!

David

[Christopher Young]

Yes, not good at all. That is really beginning to look like out of focus on the near side on one edge and out of focus on the far side on the other edge. A sign that one or more elements are not sitting parallel to the film/sensor plane. Trust you get it sorted out soon.

Chris Young

[David Anderson]

Submitted videos and photos to Lensrentals yesterday. They had to escalate it to upper management since I'm outside the 14 day window. The camera shows zero signs of ever being dropped or any physical damage so I'm curious as to how that happened.

I treat it with kid gloves and it's either on a tripod or in a pelican. I'll update as I find out more.

David

[Pete Cofrancesco]

In a span of few years I had two camcorders with lens/focus issues. Both I believe were open box specials with low or no hours. They don't need to be dropped to have an issue the manufacture had to replaced the lens. I'd imagine the manufacture would need to examine it and do the same.

[W. Bill Magac]

I’m curious how LensRental described the Z280’s condition when they offered it for sale? Do they test the cameras/lenses prior to putting them up for sale?