canon G10 aperture?

[vbsaltydog]

I got a canon G10 for tank photography and while I am no photographer, I am trying to learn the fundamentals and get out of auto mode. I thought I would use the step-by-step approach by learning each setting's effect one at a time and then combining them after I was familiar with all of the tools at my disposal.

Having said that. I am at the aperture stage and thought I would take a few shots at the lowest and highest aperture settings of my camera and then review the changes in the depth of field but after doing this .. the DOF is the same! What did I do wrong, I wonder? Any advise is appreciated.

aperture of 2.8 and 8.0 used in testing.
G10 in AV mode.
Shoot in JPEG and RAW modes.
Shot in Macro and Standard Modes.

In all cases, aperture settings seem to have no effect on the photo.

 

[TitusvileSurfer]

The aperture did have an effect on the photo but the G10's tiny sensor is masking them.

Three things effect DOF: Aperture, focal length (mm), and distance between lens and subject.
Your focal range is very small. The Canon G-10 is a point and shoot, and like all other point and shoot cameras it contains a relatively small sensor compared to a DSLR. The Canon 5D is full 35mm film equivalent camera and has a 1x crop factor. The G10's sensor is 1/5 the size of 35mm film, giving it a 5x crop factor.

The G-10 does NOT use a 28-140mm but instead shoots from 5.6-28mm. The edges of what a 35mm camera would see (80% of them!) are cut off and all off those 15 megapixels are crammed into the center. This effectively gives you a "zoom" like a 28mm-140mm full frame (35mm) camera would see. The camera took the picture zoomed all the way in at 28mm. Your only looking at the 20% of the very center of that 28mm picture though. This makes it seem like 140mm. They call this "equivalent 140mm" in the industry.

If I used a 35mm camera and took a picture at 28mm, then cut 80% of the edges off of the image, the DOF would be the same between that picture and your G-10 zoomed all the way in at "140mm".

This is both a blessing and a curse. In a reef tank we are constantly fighting too much DOF which confines the image to just a polyp or two in some cases, whether we want it to or not. Of course we have tools such as focus stacking and whatnot to combat this, but point and shoot cameras and DSLRs plays ball in a different league. All of the physics changes.

 

[vbsaltydog]

Thanks. I also tested the aperture range at farther distance items (out to about 3 feet) and was again not able to detect a change in the resulting DOF. Are you saying that the G10 is not capable of taking photos where there is a narrow DOF and all but the subject are blurred?

 

[vbsaltydog]

OK. FWIW I have been reading and doing test shots and it seems that the G10 does not do narrow DOF easily in standard mode with portrait type shots but in macro mode at close to 28mm the DOF can be manipulated fairly well with the aperture settings. I did have to go to full manual mode in order to adjust the shutter speed otherwise 8.0/fs apertures did not let in enough light to expose the shot but after tweaking a bit, macro mode + tight zoom does allow for DOF adjustments that reflect your manual settings. Having said that, it does seem that DOF is limited on shots that do not fit the macro w/zoom profile.

I am a photography noob so please correct me if any of this info is incorrect.

 

[TitusvileSurfer]

If you are close to your subject and the background is FAR away, it should blur. The G-10, along with practically all other non-DSLR cameras, are extremely handicapped if you want to creatively use DOF. I would go as far as to say all digital non-DSLR cameras. There are plenty of 35mm film point and shoot cameras which could get CRAZY depth of field (better than 90% of DSLRS).

 

[vbsaltydog]

Thanks again. I think I have a good handle on what the G-10 is capable of with DOF after several hours of testing. The good news is that I am proficient with PS so I can do the DOF that the G-10 can't in post.

 

[TitusvileSurfer]

All it needs is a little gaussian blur!

 

[vbsaltydog]

Agreed. Thanks again for all of your advise along the way. You have been very helpful.