How Does Macro Mode Effect focal length on Canon G9?

[abrogard]

I just need to input focal length to a dof calculator and I am asking about a range where the camera is in macro mode.

Will that have any effect on the focal length I should input to the calculator?

[Polar01]

DOF calculators use f/stop value you choose, and distance to subject or point of focus. Why not just try it enter the values at one focal lenght say 28mm and on at say 35mm see if any difference.

Cheers: Allan

[DanK]

I can't say anything about that particular camera. But as a general rule, when one gets close to 1:1 magnification, effective focal length increases. This is explained in one of the tutorials on this site (always a good place to start), https://www.cambridgeincolour.com/tu...cro-lenses.htm. There is also a macro DOF calculator there.

[rpcrowe]

I have an e-mount 65mm macro lens that is primarily designed for APSC Crop cameras. It will vignette on a full frame format camera until focus is up close. From about 1:2 to the native 2:1 ratio the circle projected by this lens will cover the entire full frame...

[William W]

I just need to input focal length to a dof calculator and I am asking about a range where the camera [Canon G9] is in macro mode.

Will that have any effect on the focal length I should input to the calculator?

99.99% sure: No.

As far as my knowledge extends, all the Canon Powershot Series work the same: putting the camera into “Macro Mode” allows for a closer Focussing Distance with improved AF Accuracy at the specific Focal Lengths allowed: the Focal Length of the lens does not change. *[Note 1]

In the case that your more toward a Novice than an extremely experienced Photographer and/or you have a particular passion for the Mathematics and calculating the DoF for Close Up and Macro Photography - consider that, for most practical purposes calculating the DoF for these shots will have little value as the Powershot Series of Cameras do not allow for any extensive manipulation of Lens Extensions and Aperture Control, basically you’re working in “Close Up” mode with the lens that you have and if you have enough light to stop down the lens to around F/8 and you are still able to use a relatively low ISO – the advantage you have is that the sensor is relatively small, hence the DoF will be relatively large.

WW

*[Note 1] Ignoring all arguments that (mostly) ALL Lenses will exhibit minute changes in the Focal Length as they travel through their focus range.

Additionally pls see Dan's comment re Lenses when focus of lens is approaching "Macro" i.e. 1:1. Approaching 1:1 magnification the changes are not so 'minute'.

[rpcrowe]

DOF in macro work is dependent upon the image ratio, not the sensor size. A 1:1 ratio will exhibit the same DOF regardless of the focal length or subject distance. The only difference at 1:1 ratio between a large sensor and a small sensor is the amount of area covered at that ratio...

[William W]

Irrespective of engaging in a discussion about the effects of sensor size to a comparative resultant available Depth of Field at 1:1 magnification - I believe that we will find that a Powershot G9, (the camera in question) is not capable of "Macro" in the strict sense of it being 1:1 or greater, anyway.

As mentioned the "Macro Mode", of a G9 is a selection on the camera (i.e NOT a selection of the lens), is a simple convenience to allow closer focusing than what is normally available at a set specific Focal Length Range of the Zoom Lens in that camera, and probably it also activates an advanced AF capacity at those closer focusing distances.

This was the point in Post #5 when mentioning: "basically you’re working in “Close Up” mode with the lens that you have and if you have enough light to stop down the lens to around F/8 and you are still able to use a relatively low ISO – the advantage you have is that the sensor is relatively small, hence the DoF will be relatively large."

'relatively' (twice) are the key words in the sentence: "the advantage you have is that the sensor is relatively small, hence the DoF will be relatively large". The meaning being - relative to other camera formats: that is to say, the smaller sensor size of the G9 will allow a 'relatively' larger DoF, than if one FRAMED exactly the same shot using a 135 Format camera, for example.

WW

[DanK]

I think the disagreement here is more apparent than real. What Richard says is correct, but it doesn't contradict what Bill wrote. At 1:1 you are not framing the same way with the two sensor sizes. If you shoot a FF at 1:1, you have to shoot the same subject at less than 1:1 with a crop sensor to frame the same way because the narrower AOV of the crop requires that you increase the distance from the subject.

[William W]

For clarity, I wasn't disagreeing with what Richard wrote, simply choosing not to discuss it, because, I assumed Richard was replying to what I wrote in Post #5 - if that assumption of mine was correct, then I did not explain myself concisely enough in Post #5

My response in Post #7 had several purposes, one of which was to clarify what I meant by Post #5 - especially clarifying the use of the word 'relatively' - meaning that I was comparing different Camera Formats.

WW

[DanK]

I understand. However, people who are not all that familiar with macro often misunderstand the impact of a difference in sensor size when working at a fixed magnification, so I thought it was worth throwing in that clarification.

For clarity, I wasn't disagreeing with what Richard wrote, simply choosing not to discuss it, because, I assumed Richard was replying to what I wrote in Post #5 - if that assumption of mine was correct, then I did not explain myself concisely enough in Post #5

My response in Post #7 had several purposes, one of which was to clarify what I meant by Post #5 - especially clarifying the use of the word 'relatively' - meaning that I was comparing different Camera Formats.

WW

[William W]

^Absolutely. Your clarification was appreciated and was worthwhile.

As a side comment - my opinion is that clarifications are a necessary and integral part of any quality written forum: more so than in an oral forum.

Nuances of writing and reading are more prone to misinterpretation and misunderstanding than when we speak face to face and have the luxury of: tone; rhythm; timbre and body language cues.

WW