Minute Depth of Field

[chris kippax]

Hi guys
When using my Canon g12 with a Dyron +7 diopter the depth of field is razor thin. I use Manual mode, f8, start around 1/500, Iso 80, macro mode, zoom all the way in and adjust strobe power to suit. The issue is that most times I can only get a thin band of sharp image and the rest well out of focus. As an example I took a shot of a Nudibranch a few days ago and only the Rhinophores were sharp( so a tiny portion of the image). Have I reached the full potential of compacts and need to step up to slr? Or are there other tips and tricks to obtain a larger depth of field?
Thanks

 

[chris kippax]

 

[Storker]

Have I reached the full potential of compacts and need to step up to slr?

If you think your DOF is too thin, switching to a larger sensor camera is the worst thing you can do (for DOF, that is). At the same aperture and angle of view, the larger the sensor the thinner the DOF. I have an m43 camera, a "crop" sensor dSLR and a "full frame" sensor dSLR. At the same angle of view, there's one aperture value difference in DOF for those three cameras (f/8 on the m43 is similar to f/11 on the "crop" dSLR and f/16 on the "full frame" dSLR. And it would be similar to f/4 or larger apertures on a compact, depending on the sensor size).

You can of course use smaller apertures than f/8 with some compacts, but expect some overall softening of the image due to diffraction. Unfortunately, we can't beat physics. I'm pretty certain that that's the reason many compacts won't allow smaller apertures than f/8.

 

[RyanT]

What Storker said. DOF is a product of magnification and aperture. The higher the magnification, the lower your DOF. A bigger sensor requires more magnification to fill the frame, and hence you get a lower DOF for a given aperture. I'm not familiar with the G12, so I don't know if you can stop down more than f/8. On a cropped frame DSLR, you have the option to stop down to f/32 with some macro lenses. Stopping down this far on a cropped frame DSLR will probably give you a tad more DOF than you get on the G12 at f/8, but again you'll start to see the image get a bit softer due to diffraction.

 

[rob1967]

Yes, the closer you are to your subject, the less depth of field you will have, so you generally need a small aperture (high F number) to maintain decent DOF for macro work. The G12 has a minimum aperture of f/8, which given it's crop factor of 4.6, would be equivalent to about f/36.8 on full frame. So yes, keep it on f/8 if you want to maximize your depth of field.

When you add on a diopter, you lose even more depth of field. The stronger your diopter, the more depth of field you loose. I would suggest try working with a less strong diopter, say about a +3 or so; you will find it more versatile and easier to work with. The +7 would be good only for the tiniest of critters IMHO, say less than 5 mm or so.

 

[chris kippax]

Yes, the closer you are to your subject, the less depth of field you will have, so you generally need a small aperture (high F number) to maintain decent DOF for macro work. The G12 has a minimum aperture of f/8, which given it's crop factor of 4.6, would be equivalent to about f/36.8 on full frame. So yes, keep it on f/8 if you want to maximize your depth of field.

When you add on a diopter, you lose even more depth of field. The stronger your diopter, the more depth of field you loose. I would suggest try working with a less strong diopter, say about a +3 or so; you will find it more versatile and easier to work with. The +7 would be good only for the tiniest of critters IMHO, say less than 5 mm or so.

Thanks Rob
I looked into a +3 diopter but can not find one. Who makes them and would a slr +3 be viable underwater? I found a fantasea +4 but that's it.

 

[bvanant]

shoot with what you have from a bit further away and then crop
bill

 

[chris kippax]

shoot with what you have from a bit further away and then crop
bill

When using the Dyron +7 diopter the cameras auto focus is unreliable. It has a distance that the lens is sharp and either side of that it is out of focus. You can vary the distance with the zoom. So with the camera zoomed all the way in its good focal distance is about 10inches (as per the above photo I attached uncropped), zoomed all the way in it is much closer and dof remains thin.

 

[rob1967]

When I was shooting with a compact Canon (S100), I used the RecSea 2-diopter flip macro lens (Recsea 2-Diopter Flip Macro Lens for S95 & S100 Housing). Most of the time I would use only one element, the two together was only good for the tiniest of subjects. Each element was I believe about a +3.5 diopter strength. It was ok, but the plastic became scuffed with time.

I am now shooting SLR, and have a Nauticam flip adaptor that Bill (above) was kind enough to sell to me. Flip adaptors are great because it makes it very easy to try a few shots without a diopter, and then try adding the diopter only if you are wanting more magnification. Bill is right, try shooting without the diopter first.

I use both the Nauticam SMC (roughly equivalent to a +10) and an Aquatica +5. I find the latter more versatile and easier to use, so that is the one I use more frequently now. For compact cameras, there is the Nauticam CMC, and Nauticam has just released the CMC-2 (Nauticam 2015), which looks really nice and might be exactly what you are looking for. Not as strong as the original CMC so should be a lot easier to use.

Here is a good article that you might want to check out that is specific to shooting macro with the G12: Taking Macro Shots Underwater with the Canon G12