Macro Lens Glass Distortion? How to get around it?

[RoboPhung]

Hi,

I'm trying for the first time, some aquarium photography. I tried capturing some shots of my gf's newly set up 12 gallon Nanocube, and I'm having a great deal of difficulty focusing on subjects.

I shoot with a Canon 40d and a 100mm f2.8 Canon Macro. I didn't attempt to use a tripod, but I bumped the ISO to around 800-1000, and set the appropriate aperture to obtain proper exposure for a sufficiently fast shutter speed (around 1/80-1/100 at f8-f9). I know the DOF is quite shallow at these settings when getting the camera close to the tank, but there should still be that narrow depth where everything is sufficiently sharp.

The problem is, I simply can't get a proper focus on anything. If I waited around for a dwarf hermit to crawl up right against the glass, I can get a nice sharp shot of it, but I was trying to shoot another hermit sitting completely stationary on top of a rock about 6-7 inches from the glass, and no matter what I did, the lens couldn't achieve a sharp focus.

I then tried to just test around and focus on different parts of rocks with my lens about 8" away from the glass surface, and the same effect occurred.

If I back up away from the tank maybe 4-5 feet, I can get a nice sharp 75 -80% tank shot.

The problem is that this distortion occurs when I get closer for macro.

Is this a common thing when dealing with aquarium photography?
I quickly read a couple of things that mentioned glass distortion, and that you need to shoot the camera into the glass at a 90 degree angle. But I'm just wondering, because on a nano-cube, the glass is so thin, and for a hermit to only be 6" from the glass resting on top of a rock, can the distortion make that drastic of a difference?

Thanks, your thoughts and input are greatly appreciated.

 

[juniormc8704]

its not the lens, its the curved glass of the tank.

shoot from the side walls and you wont have that problem.

 

[RoboPhung]

I tried shooting from the side as well, I still got the same blurriness.

I'm just baffled when I see all these great macro shots using a dedicated macro lens. Do they place the corals right up in front of the glass to shoot it?

 

[Recty]

I would say try and shoot straight on to the glass, make sure you're not taking a picture at a slight angle at all.

I've noticed when doing farther away shots, I can do a little bit of an angle but if I'm doing some close macro work, even a 5 degree angle makes the shot blurry.

 

[dendronepthya]

I agree, shooting perpendicular helps a lot.

 

[Reef Bass]

+1 for perpendicular being critical, crucial and megaimportant.

I will move a coral from the back of the tank to the front if I want to fill my viewfinder with a certain area of it, but not to help with any sort of distortion or lack of clarity issues. The distortion occurs because of the angle through the glass, not the amount of water behind the glass.

 

[RoboPhung]

Awesome explanation Reef Bass, I will have to try out everyone's suggestions and see if I can obtain better results.

I was just unsure at first because although not shooting exactly perpendicular, (obviously, because how can you measure exact perpendicularity using handheld), I didn't think it to be a huge factor especially if it's close enough to perpendicular. But if even 5 deg off perpendicular can make a huge difference, then that's where I'm messing up.

Also, good to know that the distance of the subject from the glass has no effect.

Thanks once again, you all were very helpful.

 

[TitusvileSurfer]

<a href=showthread.php?s=&postid=14877273#post14877273 target=_blank>Originally posted</a> by RoboPhung
obviously, because how can you measure exact perpendicularity using handheld

The fix for this is easy. Don't shoot macro hand held. ALWAYS use a tripod!!!! A quality tripod should be your next investment if you want to get the most out of your camera.