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Mirrorless Focusing

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A friend of mine picked up a Nauticam / Sony RX100 IV and we spent the last two weeks diving in Indonesia (on the Damai II). I use an SLR and have no problem with focus but he really had a difficult time using the Sony. Do you have any tips on how to focus better or is there a focusing aid that should be looked at to purchase?

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He had no problem with wide angle but doing macro or esp. macro with the CMC was very hard for him to nail the focus.

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That's because the magnification is so high that there are only few mm of range where you can focus. He needed to use manual focus with peaking. It's not the camera that can't focus is the depth of field that is not there

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Having many mirrorless and dSLRs, my findings are very similar. However, there is a trend improving. At this moment or writing, I still think conventional dSLRs offers unparalleled focusing speed for underwater macro shooting

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The issue has to do with depth of field it is true that smaller sensor have more depth of field at comparable aperture however a compact is limited to f/8 - f/11 and a micro four third or cropped sensor to f/22. A full frame sensor DSLR at f/32 has actually more depth of field at comparable magnifications me higher image quality. Especially 1" sensor compacts have this problem whereby depth of field is small diffraction is high and with a close up lens you have no room for errors. It's a common misconception that smaller sensor higher depth of field that is not an absolute truth

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I think aside from the depth of field he also has a harder time seeing that the photo is in sharp focus on the screen as compared to using a viewfinder.

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I think aside from the depth of field he also has a harder time seeing that the photo is in sharp focus on the screen as compared to using a viewfinder.

The RX100 has a focus mode called DMF that activates peaking and a complete manual mode

When you use the CMC you just have to set the manual focus to minimum distance and then move the camera until you see peaking working then shoot

It's painful but it works i have shot videos of Pygmy sea horses with this technique

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The RX100 has a focus mode called DMF that activates peaking and a complete manual mode

When you use the CMC you just have to set the manual focus to minimum distance and then move the camera until you see peaking working then shoot

It's painful but it works i have shot videos of Pygmy sea horses with this technique

 

When I am in Movie mode on my RX100iv then the DMF focus mode is disabled, regardless whether I use automatic aperture or complete manual mode. Am I missing something?

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When I am in Movie mode on my RX100iv then the DMF focus mode is disabled, regardless whether I use automatic aperture or complete manual mode. Am I missing something?

No in video you only have continuous and manual. You can use the manual toggle to stop the camera changing focus

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Hi,

 

I am by no means an expert in this field. But it is my understanding the front of the camera lens needs to be as close as possible to the back side of the diopter in order to be able to focus.

 

When using the RX100 the lens is actually moving away from the backside of the diopter when zooming in. This is probably why the photographer should avoid zooming when using a diopter. I understand it is tempting to zoom when shooting small objects. It just works very bad for the RX100 when also on the same time applying a diopter. I know this because my wife is using the RX100 mkiii with a Subsea diopter on a regular basis.

 

For mirror less and compact system Nauticam changed the design on the CMC to allow the back side of the CMC to come closer to the port/front of camera lens.

 

/Morten

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Hi,

 

I am by no means an expert in this field. But it is my understanding the front of the camera lens needs to be as close as possible to the back side of the diopter in order to be able to focus.

 

When using the RX100 the lens is actually moving away from the backside of the diopter when zooming in. This is probably why the photographer should avoid zooming when using a diopter. I understand it is tempting to zoom when shooting small objects. It just works very bad for the RX100 when also on the same time applying a diopter. I know this because my wife is using the RX100 mkiii with a Subsea diopter on a regular basis.

 

For mirror less and compact system Nauticam changed the design on the CMC to allow the back side of the CMC to come closer to the port/front of camera lens.

 

/Morten

No the whole idea of a diopter is to zoom in full through the lens there is no benefit using a zoom lens at the wide end

The camera can focus already at the focal length of the diopter so there would not be any need.

The diopter has its ow focal length once that is reached the amount you can move back and forth depends on the lens itself and the depth of field.

The nauticam cmc has a focal length on its own of 75mm if you hold it at that distance the camera is at infinity it will focus regardless of the distance between the the cmc and the lens however it will eventually vignette

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