Strange vignetting problem

Hi,

I dive with a Sony TRV 33 housed in an Amphibico Dive buddy. When I use the 120° WA port, I get strange vignetting.

Strange because it's intermittent, the vignetting moves slowly in and out of the image.

I posted a small demo of what I'm refering to here 208 KB WMV. You will see that when I bump my shoulder and the unit moves , vignetting appears and then slowly resides.

Please note that the camera is absolutely and positively NOT moving within the housing (it's the first answer I always get, getting annoying as it's obviously the very first thing I checked, and check I did many many times).

I was able to replicate it somewhat:

If the camera "steady-shot" is on

and

the unit is underwater

and

the unit is vibrating or shaken sharply

and

alignement of the camera withing the housing is not absolutely perfect.

I say somewhat because even with all those condition, the vignetting I get topside doesn't behave like it does on footage taken at depth.

I'm at a lost to explain this, anybody seen something like this before? Or any suggestion as to who I could consult to help me solve this (please don't say Amphibico...).

Thanks.

Hi, no idea what your problem may be, but I moved the topic to the video area as it may get more attention here.

Luiz

Bullshark (name?),

I have experienced a similar problem underwater with my FX1 in the Phenom housing. It almost appears as if the camera is moving in the housing (but i don't believe it is). while filming mantas in open water the vignetting would be moving back and forth. i have been told this is related to stead shot be in the "on" postition. when i tested with it in the "off" position, i did not observe a differnce. regardless, i would recommend putting steady shot in the "off" position as this has been the cause of such issues for others in the past. I would also make sure your flip filters are not moving in/out of the frame when bumped. let me know if this is of any help.

-shawn

Sorry, don't have the ability to download your clip.

Is this the Amphibico WA lens that is a push on lens on top of the other port?

What you describe makes me think that this may be the case. If you put the push on lens on top of the other port before getting in the water you will end up with an air bubble between the two which would account for the problem.

To fix you need to get into the water with the add on WA off the camera and add onto the lens once in the water

M

Is the problem only on the widest part. I used the 120 and had to zoom it in a little to fix the vignetting. Though I never seen it 'Move' at all. That might be a refraction defect caused by light abnormality in the water...

Then again it might be lens defect only seen in water.

Then again what the fook do I know...

Dive safe

DeanB

I have experienced a similar problem underwater with my FX1 in the Phenom  housing. It almost appears as if the camera is moving in the housing (but i don't believe it is). while filming mantas in open water the vignetting would be moving back and forth. i have been told this is related to stead shot be in the "on" postition. when i tested with it in the "off" position, i did not observe a differnce. regardless, i would recommend putting steady shot in the "off" position as this has been the cause of such issues for others in the past. I would also make sure your flip filters are not moving in/out of the frame when bumped. let me know if this is of any help.

And I haven't tried getting footage at depth with steady shot "off" so I'm not quite sure it is in fact the problem.

If you've looked at the footage, you can see that the vignetting is very sharp; any attempts I made at moving the camera inside the housing, or getting thing in front of the lens resulted in blurry and fuzzy looking obstruction, not the kind of sharp vignetting I get in my footage. Is that what you're getting also with your FX1?

Is this the Amphibico WA lens that is a push on lens on top of the other port?

Thanks for the reply, and thanks to the mod for moving to the appropriate forum (honnest mistake on my part, I'm kind of new around here...)

/Martin

Is the problem only on the widest part. I used the 120 and had to zoom it in a little to fix the vignetting. Though I never seen it 'Move' at all. That might be a refraction defect caused by light abnormality in the water...

 

Then again it might be lens defect only seen in water.

Do you dive with "steadyshot" on on the camera?

And it does seem to be worst the deeper I go strangely enough. Shaking the housing in my pool did give me some vignetting, but nowhere near as extreme as what I'm getting at depth nor did it behave the same.

/Martin.

Based on your clip, this looks like the standard issue with electronic stabilization with a lens that can not cover the entire sensor without vignetting.

It looks like with that lens, everything is OK as long as the image is being taken from the center of the sensor. With electronic stabilization, the image is cropped from a sensor larger than the actual image. When stabilization moves the cropped area out to the edge of the sensor, you get vignetting on that side. That slow drift you see is the stablization trying to dampen the camera movement.

If you just handhold the camera above water and really watch a fixed spot near the edge of the picture, I think you'll see that same type of "drift".

For underwater shots, you should always turn off Steady Shot/image stabilization /OIS. There are too many elements without the terrestrial gravity to make sense for OIS to work. Recently I forgot to turn it off on the first dive and it caused my clip to jump all over the place in minute but noticeable movements.

I too have noticed slight movement of the vignetting on my VX2K/Gates if I've failed to zoom in a little bit from maximum wide. I alway assumed it was slight movement of the camera or a side effect of auto focus. I never considererd the steady shot. Thanks for the tip guys!

Nick

Thanks for all the inputs guys.

It is the steady shot function which is the culprit, when I made test topside I couldn't see the effect because I was just looking at the viewfinder, but when I recorded and imported footage in my NLE I was able to see the same vignetting.

I was wrongly assuming the viewfinder to be full frame when I was testing (duh).

So, solution turn out simple, either switch steady shot off or keep it on but zoom in a little.

Again thanks, I really was scratching my head with this one.

Wow - so useful these forum discussions. I am just about to spend three days testing out my new A1+housing in the field and had convincend myself that 'steady shot' would be a useful feature to have switched ON underwater with all that motion etc. I think you guys just saved me another time-sink of angst (so common with this game.....) Thanks!

NickJ

You do know you have to switch on the WA converter mode on the A1 otherwise you'll have the same problem topside.

Ya, i learned these lessons the hard way...when you see the vignetting bobbing in the picture while editing, it's almost unbelievable that the "steady shot" could do that ...very strang. Since turning off...no issues.

System check sah!

STEADYSHOT=OFF

CONV. LENS=WIDE CONV

WHITE BAL.=ONE PUSH

MARKER SET=ALL items OFF (A1 will not send ANY data to an external monitor, eg housing LCD with any of the screen markers ON - serious angst on this for a while the other night)

what about

BLACK STRTCH=ON

FULL SCAN=??

what about

BLACK STRTCH=ON

FULL SCAN=??

With steady shot off, you might as well turn full scan on. Why throw away resolution?

I don't know about black stretch. That's part of what I want to test.

Based on what I have read, you might want to turn down sharpening a little. The camera seems to over sharpen a bit which seems to make artifacts worse, particularly in low light.

I plan to try the Cinegamma set to 1. Seems to give a less harsh tonal curve.

Good luck with your testing. It will be interesting to compare notes in a week or so.

OK good advice. Thanks for starting the other specific thread. Will report back, rushing for airport now .....