G10 Macro focus problem

[drcolyn]

Please bear with me if the question below seems like basic photography knowledge.
I tried reading up on the subject on www.Cambridgeincolour and progressed from focal length to depth of field to circle of confusion. (which is where I am now).
I recently tried taking a photograph of two soft corals as it was such a nice colour combination. The photo attached was taken in Macro mode F8 1/125 ISO 100 and the size of the corals about 2 inches. I guess that the orange cup coral (which is in focus) is centimetres closer than the purple soft coral (which is out of focus) According to the manual the focal length in macro mode is 1 – 50 cm.
Does anybody know what I did wrong not to get both subjects in focus or is the G10 simply not up to this job. Will a wide angle lens (as in wide angle macro photography) remedy the problem as I understand it will increase the focal range.

 

[dhaas]

drcolyn,

First, throw out all you know about smallest (highest number f-stops) = max. depth of field with small sensor cameras like your Canon G10. I have owned that model plus will be getting a G11 soon.

The "sweet spot" for best DOF (depth of field) due to the smaller sensor and lens is around f5.0 to f6.3. At f8 diffraction actually starts making your photos look worse (!!!!!)

Second, the DOF WILL vary with how zoomed in you were from wide angle. Small sensor P&S (point and shoot) cameras usually have the closest DOF at WIDEST angle zoom position in macro mode. It's in your manual how close you can focus in macro mode.

So if you can get your strobe light in I'd stay closer to wide zoom position, maybe f5.6 and shoot away.

Good luck!

dhaas

 

[drcolyn]

Hi dhaas

Thanks for that tip - first hand experience is just what I was looking for.
I have made a dummy subject consisting of two old toothbrush heads (don't laugh the bristles provide a nice way to see the quality of focus) and placed them 2-3 inches appart. Even out of the water I see the G10 struggling to get good focus on both. It becomes even worse when I offset them so the one is 1" closer to the lense than the other (same thing happened in the attached photo). Can the G10 handle this difference in distance or must I in future recompose so that both subjects are at exactly the same distance from the lense.

 

[Maddog59]

I'm wondering if the problem is not totally a DOF thing, as, if you have a close look at the photo it appears as if the background behind the purple coral is relatively sharp and there may be some movement of the subject due to current.

It's a little hard to tell from the image size supplied but on my sceen it does appear that way! And also the urchin in the background is sharp as well and it is further back than the Soft coral!



Peter

 

[bvanant]

Don't get confused by the statement that the focal length is 1 to 50 cm. That is the range over which you can focus on a single object, not the distance that will be in sharp focus at a given fstop. If you like I can post some pics shot with a DSLR that shows the relative DOF at various fstops.

Bill

 

[dhaas]

drcolyn,

Biggest tip I can give you is review the "Focus Mode" choices in your camera manual and try switching them around.

Most Canon models have an AiAF that uses multiple "blocks" as one choice. Whichever is closest and the camera can detect enough contrast to lock in will be chosen and lights up GREEN.

The "FLexizone" (some models have one choice labeled "Center", too) allows picking one focus point. You have to aim that at your prime point of interest do a half press" to achieve focus lock. Then recompose before pulling the trigger.

Find these choices in your manual and practice with your camera out of the housing while high and dry

Many newer models have "Face Detect" too which I have yet to try on fish. It does use EYES to lock on is my understanding so it MAY work for critters!

Headed to Cozumel myself this Saturday with a couple of new toys similar to your gadgets.

Will report back after 12/14!

dhaas

 

[kaaralex]

Hi drcolyn,

macro on G10 is wonderful, i've done hundreds of great shots on land. it also works pefect with built-in flash, whose output i think must be compensated in macro mode, coz the pics are rightly exposed.
u must keep in mind, that even at smaller aperture, the longer the zoom, the shallower DOF. at the longest end it is just A millimeter. (see below shot) add currents and buoyancy to it... challenging. its more practical to get as close as possible. also, set AF focusing area size to "smaller" (there are only two options on G10), so the camera focuses on your subject and not on something behind it.
what i personally find the most challenging with UW macro on G10 is not DOF, but light. u can hv everything in focus, be buoyant as a jellyfish and STILL dont get satisfying image. i m getting a better strobe to see if the problem is really with light, or with somebody else.

enjoy your diving, L.

 

[drcolyn]

Hi All

Thanks a lot for all your inputs. I certainly have a lot of experimentation to do.
I think Maddog59 was right about the wave action causing a bit of a blurr as the background is not that out of focus. "Good" diving conditions on the west coast of South Africa is 20 ft viz, water temp 13 deg. C and 1 ft swells so I considder myself lucky to have had the opertunity to dive this spot. I added some more pics just to give you an idea why I like this spot so much.