Macro focus v auto focus

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Originally Posted by CatherineA

Thank you so much Dan! I was a bit worried when I posted the question because I knew it was really basic but everyone has been very patient and very helpful. What you have said about depth of field with macro also helps me understand why a photographer needs a tripod for macro work. I knew it was always preferable but I see why it is especially called for with macro.

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Don't worry about posting basic questions. You can see that there are plenty of folks that will help out. After all, we were all beginners once.

If you haven't, you might want to look at the many tutorials on this site. Some are still too advanced for where you are, but there are some that cover the basics, and they do it more systematically than our ad hoc answers generally do.

Thanks Dan! And yes, the tutorials are excellent. I’m thinking of treating myself to the CIC book.

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Originally Posted by george013

I don't know how it's archieved but it looks like the lens system is moved a little forwards. In that case you can focus on closer subjects but not at infinity anymore.

George

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In most cases, the focusing mechanism will extend more, much like a built in extension tube. Some of my zooms have a focus limit switch to that the AF doesn't move through the complete possible range. For example, the 200-500 has an option for FULL range or 6 meters to infinity. Putting limits on the AF helps it focus faster.

In the case of a P&S like the P900 I suspect that the macro setting is the limit control and operated by removing the block rather than setting it.

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Originally Posted by Saorsa

In most cases, the focusing mechanism will extend more, much like a built in extension tube. Some of my zooms have a focus limit switch to that the AF doesn't move through the complete possible range. For example, the 200-500 has an option for FULL range or 6 meters to infinity. Putting limits on the AF helps it focus faster.

In the case of a P&S like the P900 I suspect that the macro setting is the limit control and operated by removing the block rather than setting it.

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Set the camera/lens on macro and try to focus on infinity manual or auto. That might give some idea.

George

Catherine, your question was not basic but rather camera specific and the manual does not provide the full answer. What it says though is that minimum focus distance changes continuously from 50 cm to 5 meters as you change focal length. It also says that if you enable macro mode at the widest position, you can focus anywhere between 1 cm from the lens all the way to infinity. The manual is not very clear on what happens when you start zooming in while in macro mode. Page 41 of the manual indicates there are at least two regimes here and the camera will display different symbols. You have got the camera, you can test how close it can focus with and without macro mode enabled at different focal lengths.

Thank you Dem. This morning I experimented again and when I placed something in my hand to take the place of a bird in my hand, I could take photos both in macro or AF and the camera showed the different symbols. I can’t see a difference in the results but initially I wondered if there were subtle differences that I wasn’t picking up on. Now I see your point though, it is a camera specific question.

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Originally Posted by CatherineA

Thank you Dem. This morning I experimented again and when I placed something in my hand to take the place of a bird in my hand, I could take photos both in macro or AF and the camera showed the different symbols. I can’t see a difference in the results but initially I wondered if there were subtle differences that I wasn’t picking up on. Now I see your point though, it is a camera specific question.

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When the subject is in focus you won't see any difference. It's the ability of the camera to focus on subjects at closer distance and so archiving a higher magnification.

George

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Originally Posted by CatherineA

Thank you Dem. This morning I experimented again and when I placed something in my hand to take the place of a bird in my hand, I could take photos both in macro or AF and the camera showed the different symbols. I can’t see a difference in the results but initially I wondered if there were subtle differences that I wasn’t picking up on. Now I see your point though, it is a camera specific question.

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I wouldn't expect to find a difference in the final image. The lens, sensor and processing are all the same. The only difference is a setting that affects minimum focus distance.

At 50 CM for the Normal range close focus distance I suspect that the camera could focus within normal or macro range to get your hand or a bird in the field of view.

Thank you George and Brian! Sure took me a long time to understand this, I really appreciate your time.

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Originally Posted by CatherineA

Thank you George and Brian! Sure took me a long time to understand this, I really appreciate your time.

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Here's a link with some flash applets considering photography. There're more on the internet but I found these ok.
https://graphics.stanford.edu/courses/cs178-10/applets/

George

Thank you George, that’s interesting information. I’m enjoying learning this.