Diopter with Canon 100mm macro lens seacam

I've recently bought a 100mm canon macro lens to go with my canon 5dmkii and am looking to get some super macro shots and want to buy a diopter to achieve this, I've never used one before. I use a seacam housing and have a tapered seacam macro port. Can anyone recommend diopter options that would be compatible with my seacam kit and what I need to consider when buying a diopter? Any useful source material or sources of information?

Any advice will be much appreciated!

Many thanks,

Matt

As you are shooting with 100mm lens a +4 diopter filter would work. But as you increase magnification your depth of field goes down. I have used B&W filter on my 85mm lens and it works very well. Here is the B&W website to show the difference each magafication does. 

https://schneiderkreuznach.com/en/photo-optics/b-w-filters/filtertypes/nd-100-series-1/close-up

4 hours ago, mattmarinegreen said:

I've recently bought a 100mm canon macro lens to go with my canon 5dmkii and am looking to get some super macro shots and want to buy a diopter to achieve this, I've never used one before. I use a seacam housing and have a tapered seacam macro port. Can anyone recommend diopter options that would be compatible with my seacam kit and what I need to consider when buying a diopter? Any useful source material or sources of information?

 

Any advice will be much appreciated!

Many thanks,

Matt

Since you have the tapered port the best option would be to either get the dedicated wet diopter lens that Seacam sells for it or get the Seacam 67mm adapter for the port and use one of the many 67mm wet diopter lenses available on the market.

If you go for an internal (dry) diopter you will need to have enough room between your 100mm lens and port glass for the diopter to fit. Diopters are actual lenses so thicker than filters which are flat. As well you will get fewer lens aberrations if you buy an achromatic diopter which are thicker still (and more expensive).

Wet diopters can be removed during a dive whereas you are stuck with an internal one for the dive.

You would certainly want to add a wet diopter I think to be able to remove it while diving as otherwise you will have a very restricted focus range the whole dive.  I would suggest starting with a lower powered diopter.  For example the the SMC-1 with a Canon 100mm macro lens will achieve up to 2.2x and only focus between 45 and 89mm from the end of the lens with very little depth of field.

You could then consider how you would like to mount the lens, the basic options being screwing on, flip holder and a bayonet system.  It appears you will need a 67mm adapter to use some of these options.

If you have not seen this post I recommend checking out this wetpixel live video: 

View archived post in: Wetpixel Live: Macro Close Up Lenses

I use a port made by SAGA that allows me to use M67 threaded close up lenses with my Seacam housings.

For me, the problem with the longer focal length macro lenses is their minimum focus distances makes lighting challenging. Seacam's push-fit diopters do a great job of reducing the focus distance, which is a bonus, but don't offer much magnification increase.

For super macro - I use both the Nauticam SMC-1 and Inon UCL-90 with my SAGA port. Both are optically very good. The Nauticam struggles with internal reflections when backlighting, and the Inon does not seem to have the same issue.

Thanks so much every one for your very useful advice. I really appreciate it.