Test images - 5d mkii + Sigma 150mm

Hello everyone,

I picked up an Aquatica housing for my 5d mkii.

Along with the housing I added the 18430 Mini Macro Port and 48458.

With these two ports, the macro Sigma 150mm f/2.8 fits.

The lens is about 140 to 150 mm in length.

With the two ports, there is an gap of air between the lens and the flat port lens. About 2 inches. Maybe a bit less.

I used a 4500 lumen video light.

Photographs were taken with :

1/100 - ISO 1000 - Aperture ranged between f/8 and f/22.

My question is, am I not getting the focus right? Or am I shaking too much?

Or is the combination of ports preventing the camera from focusing?

Thank you.

Photographs straight out the camera in jpg (and standard picture style):

https://imgur.com/a/pnPKJo5

What shutter speed are you using, is it 1/100 for all the images?  it needs to be high enough to prevent movement.  The old 1/focal length rule is a good starting point, you want at least 1/150 - but for closeup work you will want more 1/250 - 1/500 at a guess.  I would suggest 1/100 is marginal for this lens.

The better solution however is to use a strobe - it freezes the motion and provides way more light than the video light.  Then you will be able to use ISO100-200 and get the best out of your sensor and not worry about camera shake.

It also looks to me like you are having trouble hitting focus, the problem with the 150mm macro is there is too much working room for underwater work, such lenses tend to have the AF grab onto particulates rather than the subject, particularly if you are going from close focus to further out for a bigger subject.  This is why people don't use long macro lenses UW.  You may not want to hear this but there is a reason why 100mm macro lenses such as the Canon 100mm f2.8 are so popular underwater - they work.  Even then they are probably not the best lens to shoot morays and scorpion fish unless they are quite small - you end up with too much water between you and your subject.   I really like long macro lenses on land - but there is absolutely no way I would want to take one underwater.

so focus is out and shutter speed too low

What AF are using? - you should use a single AF point so you know what the camera is focusing on, either move the AF point around or use back button focus to achieve focus and recompose.

You also need to be very stable in the water, for macro and near macro work you need to need a very good handle on buoyancy- even with strobes to can't be moving back and forth with respect to the subject as your depth of field is so narrow you will be coming in an out focus.

If you want to persist with the 150mm try manual exposure, 1/250 and f11 with auto ISO if you have that as an option.  Or better yet shoot with a strobe in which case you want manual exposure 1/200 (max sync speed for your camera) , f11 ISO100 or 200 with the strobe providing exposure control on manual.  Concentrate on finding smaller subjects to shoot and get in close.  Once you master that you might want to move the aperture around a little and compensate with more strobe power.

Chris, first of all thank you for your attention and help here. 

I was using 1/100 for all photographs.

I planned on using manual mode, but on the boat, the housing wheel that makes contact with the camera aperture wheel wasn't making contact. The camera, somehow, was sliding too deep into the housing - thus the housing wheel was behind the camera wheel. I will remedy this by adding a little strip of velcro to prevent the camera from sliding all the way in.

In aperture mode, on my camera, the aperture wheel is another wheel. So I set it to ISO 1000 and 1/100.

Majority of photographs were at f/10. Except the last few where it is obvious I went to a small aperture (f/14 - f/18 - f/20).

I am familiar with cameras and somehow it completely slipped my mind to match minimum shutter speed to lens focal length - i.e: at least a shutter speed of 1/150. Kicking myself for the "cant see the forest for the trees" moment.

This happened because I read a few "introduction to underwater photography" articles and the majority suggested between 1/100 and 1/160. I realize why now - they were using wide angle lenses haha.

I am using the center focal point on my camera. It is the highest performing focus point. And of course I use the back-focus button. I found myself focusing, locking the focus by holding down the BF button, then gently moving myself forward/backwards to get the subject in focus - a human dolly. As you would traditionally with a tripod.

Regarding the focal length 150mm and mis-focusing due to working distance. Very true. Majority of the time I had to press the focus button several times for it to lock on to. While both the camera and lens focused very quickly each time, it still did mis-focus quite a lot. Because I am using a "proprietary" lens - I am unsure which focus ring could/might work.

My rig is very light - I am using three positive-buoyancy floats. I may jettison one for a bit of added negative buoyancy.

My question is, how much air gap should there be between the lens and the flat port lens?

I'm asking because I currently have quite a bit of air/gap.

Does this gap matter or affect anything? Focusing? Light entry into sensor?

I'm asking because at this point I can either procure another port that reduces the empty gap between lens and flat port lens - about $350.

Or procure a used Canon 100 L, the designated port, and focus ring - $1,700.

And if it becomes clear I need a strobe(s), thats further purchasing.

Not trying to skimp or anything. Just trying to see if I can make the Sigma work.

If I can, well and good. If I cannot then it'll be option B.

Next dive, I'll try 1/150 or faster and f/11 or thereabouts and manually control ISO.

Thank you very much.

The only concern with the air gap is losing working distance as long as it does not vignette.  Also closeup diopters to get better than life size won't work as well with the air gap. 

Regarding the lens the Aquatica port charts list the Canon 100mm f2.8 as needing the 18430 port plus a 48455 (25mm) ring, so you can use the port you have now and just need an extension ring.  I would suggest holding off on buying the focus gear you may find the AF works just fine and can always but it later. depending on the lens they can be very slow to focus with a focus gear and generally work best to touch a lens that has locked close to where it needs to be and often rocking back and forth is easier. 

If you want to take a step at a time you could buy the 25mm 48455 ring and stack it with the 16.6mm 48456 and that will reduce your air gap by 22mm (63.55 -25 - 16.5 = 22) and you could then buy the 100mm f2.8 later and use it with the 48455.

Regarding the strobe, if you are doing still images, a strobe is a no-brainer,  it will make a big difference to your shots.  Also you do not want a positive rig , slightly negatively buoyant is a lot easier to use.

I found this information from : http://achtel.com/Optics/

Further, when shooting through a flat port, the distance between the lens and the port should be as large as possible. This has two advantages: it reduces the angle of view and subsequently reduces chromatic aberrations and shape distortion as well as provides longer path for light through the air and shorter through the water, which improves the image clarity.

Hello everyone,

So here is the camera in the housing with the 150 lens.

In the first photograph, you can see that approx 99mm of the lens juts out the housing.

And in the second photograph, with the flat port sitting directly on the lens, the gap between the housing and flat port is approx 35mm.

Note that:

1- the measurements of Aquatica ports are based on what you see - not what get screwed in to the housing or other port.

1- I will need at least a 35mm port + 2 or 3mm - so that the lens is about 2 or 3 mm away from the flat port lens.

Posting this here for a sanity check.

Thanks

You can look for a 100mm USM Macro Canon lens (you can find cheap ones and that lens is super sharp and quick focus). It will be much easier to work with. 
For Macro work you need to have strobes. 
I would not buy extensors for that lens. 
Once again, almost nobody uses that lens…. If the pros do not use it…. I think there is no need to say more.