G9 X - Picture edges unfocused on close range

[AnthonyD]

I just bought a PowerShot G9 X.

For close range photos the center focus is good, but the edges are out of focus. I've partially overcome this effect by selecting an edge for the focus frame, but then the center is out of focus though not as bad as the edges were. No matter what I try the focus is uneven and makes for bad close range photos. This camera is brand new.

My older,  lower-end PowerShot A2500 HD manages to focus the whole shot evenly. See the attached photo comparisson.

My two questions are:

1) Is this normal or is something wrong with my camera?

2) If this is normal, can I change it so the focus is even across the image?

Thanks!

PowerShot G9 X

(not the mark ii version)

[John_]

 Since the print you took a picture of is all at the same distance all of it should either be in or out of focus. How close was the lens? And was it in Macro mode? Pehaps it was your close distance at a slight angle and you were not in Macro mode? If not try macro mode and check the focus specs vs. distance and shooting modes for your camera. I do hope it is not something wrong with your new camera. Others will respond too with more advice. Since it is new you can call Canon for help as another option.

[AnthonyD]

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@John_ wrote:

 Since the print you took a picture of is all at the same distance all of it should either be in or out of focus. How close was the lens? And was it in Macro mode? Pehaps it was your close distance at a slight angle and you were not in Macro mode? If not try macro mode and check the focus specs vs. distance and shooting modes for your camera. I do hope it is not something wrong with your new camera. Others will respond too with more advice. Since it is new you can call Canon for help as another option.

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I took several different shots and they are all like that. There was a bit of improvement at acute angles, where there normally should be problems. Yes, I deliberately set it to macro mode for some of the tests, with the same result. I tested at distances from 5 cm to 1.5 feet and the effect is still there. Longer distances seem also affected but much less.

Here is a shot with me placing the focus frame on the edge, I don't remember if it was right or left, but either way improves the edges somewhat but blurs the center.

[ScottyP]

On every lens the edges will be less sharp than the center.  Additionally, some lenses, even expensive ones, notably like the Canon EF 50mm f/1.2, the field of focus is not a flat plane but rather a curved shape so that the edges will always be out of focus.  

[ScottyP]

If you are serious about photographing text get a tilt shift lens.  If you are less serious but need to do it, use a normal lens but a high f/stop for a thick depth of field in focus. 

[Waddizzle]

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@ScottyP wrote:

On every lens the edges will be less sharp than the center.  Additionally, some lenses, even expensive ones, notably like the Canon EF 50mm f/1.2, the field of focus is not a flat plane but rather a curved shape so that the edges will always be out of focus.  

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What he is describing is the primary fundamental difference between a conventional lens and a macro lens.  A conventional lens creates a curved plane of focus with the image sensor at the center of the arc.  A macro lens produces a much flatter plane of focus.

Under most conventional shooting scenarios the curved focus plane of conventional lens goes largely unnoticed, because of the larger depth of field that you find associated with larger distances to the subjects that you have in most shooting scenarios: i.e.; a photo of your dog, or a bridge.  

The large distance to the subjects, creates a large radius, and a fairly flat focus plane.  The curve becomes irrelevant because by the time the plane curves outside of a flat DOF, the distance to the camera is so great that subjects are out of focus, anyway.  Many shots that seem soft o the edges are soft because they should be.  Objects at the edge of the frame are outside of the curved DOF.

When you start taking photos on a macro scale, the depth of field becomes much smaller, and the short radius of the focal plane comes into play.  This is why your images seem to lose focus as you move away from the center of the frame, which is where the focus plane intersects the subject.  

The flatter image plane of a macro lens reduces the apparent loss of sharpness at the edges when photographing flat subjects.  Also, this flat plane of focus makes it easier for software to perform what is known as image stacking of a set of macro images.  Image stacking combines a set of sequence of photos of a subject, where each photo has only a portion of the subject in focus, into a single composite image where the entire subject is in focus.

[MikeSowsun]

One thing to note is that the G9X has a much larger sensor than the A2500, and that means less Depth of Field for a similarly framed image. That could explain why the A2500 is better able to get sharp corners.

[Waddizzle]

I frequently eyeball this table before I go out on a shoot.  Select a camera with the same sensor size as yours.

http://www.dofmaster.com/doftable.html

It helps me to select lenses, and choose focal lengths.  It is a bit dated, when it comes to camera selection.  But, the size of sensors really has not changed.  For example, I select the EOS 7D when I am using any APS-C DSLR by Canon.

You have to scroll way down the list to find PowerShot cameras.

[AnthonyD]

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@Waddizzle wrote:

I frequently eyeball this table before I go out on a shoot.  Select a camera with the same sensor size as yours.

http://www.dofmaster.com/doftable.html

It helps me to select lenses, and choose focal lengths.  It is a bit dated, when it comes to camera selection.  But, the size of sensors really has not changed.  For example, I select the EOS 7D when I am using any APS-C DSLR by Canon.

You have to scroll way down the list to find PowerShot cameras.

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I don't mean to be rude, but what the hell am I supposed to do with that chart? I'm not a photographer, just a regular point and shoot person. The only part that I could make sense of is "Circle of confusion".

[John_ · Accepted solution]

Anthony I'm just a point and shoot person too your camera is new and if I were you I'd call Canon and see if they have any ideas outside of buying a different camera and lenses etc.etc or if maybe they will replace yours with a new one. I still don't think what your seeing is normal and it makes no sense how it switches from bad middle to edge focus....get it on record contact Canon. I looked thru your manual and saw no "disclamers" like you can expect poor edge or center focus if you shoot like you did.