Need help identifying a lens problem

I'm shooting a Sony HC-9 in a Light & Motion Bluefin housing with a standard 80 degree wide angle lens and am sometimes getting a strange white speck in the frame. It's not a bubble on the lens. It only shows up occasionally.

I've circled it in white on this frame grab:

Any help would be appreciated.

Showing up in the same spot when you do see it?

Showing up in the same spot when you do see it?

Yep, same spot. (roughly)

Also forgot to mention that the record lamp is turned off.

Yep, same spot. (roughly)

Also forgot to mention that the record lamp is turned off.

I would've first guessed it to be an out-of-focus bubble before I read your whole post.

I noticed there's a silver button on the left side of the HC9 lens barrel. Think there could be external light reflecting off it? How much play is there in the Bluefin mount? Maybe there's just enough to allow a little light to pass the front of the lens. I had a similar problem with an old poly housing, if the lens wasn't flat up against the port, I'd get strange reflections when shooting in bright overhead light.

If it was the record lamp, I think it would be red.

Looks like a reflection of some sort.

 

I would've first guessed it to be an out-of-focus bubble before I read your whole post.

 

I noticed there's a silver button on the left side of the HC9 lens barrel. Think there could be external light reflecting off it? How much play is there in the Bluefin mount? Maybe there's just enough to allow a little light to pass the front of the lens. I had a similar problem with an old poly housing, if the lens wasn't flat up against the port, I'd get strange reflections when shooting in bright overhead light.

 

If it was the record lamp, I think it would be red.

The silver button has one of the housing controls touching it. There isn't any play with the mount

at all. It's got to be a reflection of some sort since it comes and goes on the same dive depending

on lighting conditions. I've been thinking of taking a sharpie and blacking out the Carl Zeiss, Sony, etc.

on the front of the lens barrel just to be safe but I doubt that is what's causing it.

I think you will find the spot is caused by reflection of light that enters the housing via the clear side control plate.

The reason it is intermittent is that the window is often obstructed from getting direct light and so is not always a problem

This can easily be remedied by either blacking out ( or other covering ) the clear port or by fitting a shield to stop the transmission of light.

My suggestion would be to use strip of neoprene fixed to the inside of the housing that acts as light shield. The camera will scrape past the neoprene when it is inserted in the housing and the neoprene will form / mould along the side of the camera and have the required light blocking effect thereby eliminating the annoying little spot.

Beers will be fine.

Anything else shiny inside?

I think you will find the spot is caused by reflection of light that enters the housing via the clear side control plate.

 

The reason it is intermittent is that the window is often obstructed from getting direct light and so is not always a problem

 

This can easily be remedied by either blacking out ( or other covering ) the clear port or by fitting a shield to stop the transmission of light.

 

My suggestion would be to use strip of neoprene fixed to the inside of the housing that acts as light shield. The camera will scrape past the neoprene when it is inserted in the housing and the neoprene will form / mould along the side of the camera and have the required light blocking effect thereby eliminating the annoying little spot.

 

Beers will be fine.

I assembled the housing and camera without the lens to see if I could see anything that would reflect light. I doubt it's the window but it sounds like you've experienced this problem so I'll trust you and try to experiment and see if I can recreate it in the water. If you're right, I owe you a Guiness or three.

I see something similar with an HC-7 in a Gates housing when sunlight enters the back of the housing, reflects off the polished barrel of the camera, and then bounces off the port into the camera. Keep experimenting with your setup to see if you can isolate the cause. If it is light bouncing off the barrel, putting a barrier in the housing or black tape on the barrel may fix the problem.

Pat

I this weekend put a Sony HC7 in a Gates housing for the very first time, and shot some tests in a pool.

I noticed a similiar Diamond shaped spot in my videos in some scenes. Mine however was almost dead center, slightly upper in the frame. However my object appears DARKER than the background subject, and only appears when the subject is very high key, i.e. like the wall of a sunlit pool. The object in my shots does not move at all. As I pan, it remains fixed in location in the screen, nor does it change in darkness nor intensity. It is consistent, but only seems to dissapear when the subject is darker than a bright white.

But whats really odd I also noticed that in shots with the CC filter inplace or in somewhat less high key shots, the "spot" is gone. It dissappears totally in not so very bright lighting, darker shots.

Perhaps mine is just a speck of dust or such somewhere in the optics.

After taking the camera out of the housing and setting the shutter speed to Auto, it has gone away. Its definetly not a bubble, as those were crystal clear and in focus on my port. (that Fathom WP25 port is amazing!)

My tally light has been turned off on the camera. And the lens barrel shiny portions "blackened" with a ink pen (or so I think) I have yet to blacken the wording on the lens itself, but thats next.. Perhaps I need to look for dust in my camera lens itself. The port looks perfectly clean.

I was throwing together some stuff I shot last weekend and noticed it appears in other places - even on the opposite side as before.

Interesting....

Hey Cdoyal, I was pondering your reflection..

Is your screenshot example taken from the video movie or was that taken with the "still" photo mode of your camera.

The reason I am asking: if the reflection appears when taking still images then perhaps the Video camera's built-in flash is going off inside your housing and causing the reflection.

I make sure that I set my HC7 in both video and still modes to no flash prior to closing up the housing.

Hey Cdoyal, I was pondering your reflection..

Is your screenshot example taken from the video movie or was that taken with the "still" photo mode of your camera.

The reason I am asking: if the reflection appears when taking still images then perhaps the Video camera's built-in flash is going off inside your housing and causing the reflection.

I make sure that I set my HC7 in both video and still modes to no flash prior to closing up the housing.

Good thought but no, it's a frame grab from video.

I did have an interesting experience today though. The housing is sitting on a shelf in a room full of windows. The front port/lens is off the housing but the camera

is mounted in the housing. As I walked past it, I saw a sparkle out of the corner of my eye and it was sunlight reflecting off the beveled area of the camcorder lens barrel.

I bet light is coming in through the front port and reflecting off that shiny, black beveled area on the camcorder lens. Now I'll just have to figure out something

to cover it with and see if it helps.

I saw a sparkle out of the corner of my eye and it was sunlight reflecting off the beveled area of the camcorder lens barrel.

I bet light is coming in through the front port and reflecting off that shiny, black beveled area on the camcorder lens. Now I'll just have to figure out something

to cover it with and see if it helps.

I'd bet that is the culprit.

You have a HC9 right? and that is supposed to be black all over, I have a HC7 that is not. That same bevel corner (actually there are two beveled surfaces on my camera), I had to whip out a "marks a lot" black felt tipped pen, and I "painted" all around my bevel edges the lens barrel. It sure makes the camera a bit ugly.. but hey.

I considered screwing into my lens a Cokin 39mm A Series adapter. Its basically piece of black aluminum, but had a large outside diameter and could bock out these reflective surface. The problem is however in my housing there is no clearance to attach this adapter, it interferes with the CC filter holder.

Another crazy idea.. perhaps "paint" the bevel surface with either flat black modeling paint, available at a hobby shop, or Ive also heard of "gunsight" paint.. that again is supposed to be flat black and non specular. Just some ideas.

I considered screwing into my lens a Cokin 39mm A Series adapter. Its basically piece of black aluminum, but had a large outside diameter and could bock out these reflective surface. The problem is however in my housing there is no clearance to attach this adapter, it interferes with the CC filter holder.

That's a good idea. I could just remove the cc filter since I don't use it anyway.

Or better yet, how about a rubber lens hood trimmed to shape?

That's a good idea. I could just remove the cc filter since I don't use it anyway.

Or better yet, how about a rubber lens hood trimmed to shape?

I like the rubber lens hood idea.. especially if you could make it extend and fit snug against the inside the dome then you'd have a perfect light tight solution. I may consider doing that for my macro port. Great idea.

I like the rubber lens hood idea.. especially if you could make it extend and fit snug against the inside the dome then you'd have a perfect light tight solution. I may consider doing that for my macro port. Great idea.

That's just the thing, you can roll it out to fit the opening. I think it might just be the ticket,

especially since the lens on the camera sits perfectly in the center of the opening.

Is the reflection always an almost perfect square as shown above? Just curious. An example of stuff I've done with still shooting is when I have hexagonal shaped backscatter. Its air bubbles on the port. I'm not sure how relative this is to video but I did notice it was odd that it was almost a perfect square.

I like the rubber lens hood idea...