Interesting phenomenon, why do eyes see perfectly sharp but a lens cannot focus in aquarium?

I have been taking shots of a new planted aquarium (COVID project:-)) I setup. I know about refraction and all that and know there will be issues with photos where the light is traveling through water and glass (acrylic in my case).

One interesting phenomenon I notice is that I can only get in-focus shots if I am shooting with the lens parallel or close to parallel with the glass and at the level of the subject (i.e. light path is perfectly perpendicular through the glass). If I attempt to "shoot down" at an angle at a subject (through the glass and water), like getting a partial top view, my lenses cannot focus at all.

My Panasonic cameras have manual focus assist where you get a 6x magnifier box and can see if fine details are in-focus.  The lens will not focus at all on anything. There is a point where it is "least blurry" but at no point can any part of the subject be brought into focus unless per above, I drop the camera down so the light path is perfectly perpendicular through the glass.

The interesting part of this phenomenon is that when "shooting down" my eyes see a perfect sharp crisp subject while my camera lens cannot.  Is this due to having a brain to process the image or because of having two eyes vs. one lens?  Or just some limitation of cameras?

kelpdiver wrote:

Jeeter001 wrote:

The interesting part of this phenomenon is that when "shooting down" my eyes see a perfect sharp crisp subject while my camera lens cannot. Is this due to having a brain to process the image or because of having two eyes vs. one lens? Or just some limitation of cameras?

I wonder if this is a matter of our brains processing the continuous read into sharpness, same way that we are happy with 24 frames per second on film movies. The individual frames aren't great, but continuous works as our brain fills in the bits.

I would have suggested your manual focus test, perhaps not a 6x zoom however, unless you're using a tripod. At that level of mag, your ability to keep it steady is questionable.

Personally I struggle a bit - brain hurts when I look at the extreme angles. Now I want an aquarium to try this out. Also wonder if the home size, where the acrylic is relatively thin, is different from the large aquariums with hundreds of thousands or millions of gallons and much thicker panels.

IBIS and optical stabilization make it plenty easy to keep the image steady, even when looking at a 6x digital zoom for manual focus assist.  I'm usually using my 30mm macro  (60mm equiv) so that is not hard to steady that, even without IBIS & I.O.S.

That is an interesting similar phenomenon.  When we look at the individual frames in a movie they do not look nearly as nice as the fluid movie, our brains either sharpen it up for us or some other trick at play.

Does your camera use some sort of infrared focus assist?

I'm suspecting your camera is focusing on the acrylic itself.

PHXAZCRAIG wrote:

Does your camera use some sort of infrared focus assist?

I'm suspecting your camera is focusing on the acrylic itself.

No I am in manual focus mode, turning the focus ring.  That's what interesting about it.  If I turn the focus wheel while looking through the EVF the image gets less blurry to a point and then starts getting more blurry.  It never reaches focus.  There is no feature in the image that ever comes into perfect focus.  If I drop the camera down so the light path is near perfectly perpendicular with the glass, then I can get features in the image to come into focus.

Here's an illustration of what I'm talking about:

Jeeter001 wrote:

PHXAZCRAIG wrote:

Does your camera use some sort of infrared focus assist?

I'm suspecting your camera is focusing on the acrylic itself.

No I am in manual focus mode, turning the focus ring. That's what interesting about it. If I turn the focus wheel while looking through the EVF the image gets less blurry to a point and then starts getting more blurry. It never reaches focus. There is no feature in the image that ever comes into perfect focus. If I drop the camera down so the light path is near perfectly perpendicular with the glass, then I can get features in the image to come into focus.

Here's an illustration of what I'm talking about:

Nice illustration...

It may have to do with the border angle for total reflection that demand domeports for wide angle photography UW. When you exceed this angle it will not be possible to see into the aquarium at all. When you adjust the zoom of your camera to give similar angle of view than your eye, the images must be the same (the retinas are just the sensors of our internal cameras (our internal sensors are, however, curved, not flat, what also could make some difference under borderline conditions)). Position of camera and eye must be exactly identical, not just roughly similar, to make comparisons meaningful...

It also may be that you just exceed the focus range of your camera and you are too close: when going further away with the camera, the picture should become sharp then...

It would be helpful to present an "unsharp" image from your camera, so that we know what you are talking about...

Wolfgang

Got it.

It it interesting. What does 'the transition' look like, when you gradually move the camera from perpendicular to a problem angle? Does the phenomenon creep across the frame? Show up suddenly?

A couple of shots would be nice, so we can see what the camera is doing.

Also, is this strictly angle, or does moving the camera farther back help any?  Wondering if minimum focus distance has changed.

Depth of field issue. When you focus, you open the diaphragm of the camera to fine tune the focus. With the tilted view, consider it like a tilt-shift pense on your camera. Our eyes have a great depth of field, camera doesn’t.