Comparison of AF speed/accuracy on mirrorless FF

[Architeuthis 140]

I start to decide which mirrorless FF system to acquire and ask for help. At present, no system offers a complete set of lenses for UW with the corresponding mirrorless mount. While I think that adapted DSLR fisheye lenses (except Nikon where some DSLR lenses do not work properly, even with native Nikon adapter) will not be a problem at all, macro lenses with focal length around 100mm certainly may be. This will be an important factor for decision making. There are plenty of reports/reviews of a single lens existing, but what is fast and accurate, is certainly a subjective statement, especially when there is no practical experience with other systems and therefore no comparison...

Therefore I would greatly appreciate if UW photographers that have practical experience with more than one macro setup could state, how they would rate AF speed/accuracy (and eventually also other relevant features) of the different system configurations in comparison (and maybe relate to more common setups as e.g. Oly EM1II with Zuiko 60mm macro (this is what I personally have at present) and/or Nikon 105 mm macro on D8xx):

 

#1.: Sony A7RIV (or RIII) with:

Sony 90mm macro, native E-mount

Sigma 105mm macro, native Sony E-mount

Canon 100mm IS macro, adapted via MC11to Sony E-mount

=> While Sony seems to be the most mature mirrorless FF system at present, there are several reviews and reports by users here, that state AF speed of the Sony mount macros is very slow. I found a remarkable statement by Backscatter's Jim Decker, regarding the A7RIV: "For macro, the Canon 100mm IS macro lens with the Sigma MC-11 Mount Converter focuses much faster than the native Sony 90mm macro. ...": https://www.backscatter.com/reviews/post/Sony-a7R-IV-Underwater-Camera-Review

Can this be real and if yes, how is performance of Canon 100mm IS on A7RIV compared to the same lens on a Canon R body???

 

#2.: Canon R5, R6 or R with:

Canon 100mm macro, EF-mount adapted with Canon adapter

Canon 85mm macro, native RF mount

 

Thanks, Wolfgang

 

Edited March 2, 2021 by Architeuthis

[Barmaglot 230]

Maybe I don't have high expectations, or maybe it's lack of comparison points, but I've been shooting a Sony 90mm on an A6300 body for a couple of years now, and I find the autofocus speed to be quite adequate. So long as I can hold the camera still, it almost always finds focus within a couple seconds of me half-pressing the shutter. On a newer body like A7IV it should perform even better. I do, however, stay away from small, rapidly moving targets - something like a nudibranch on a hydroid that is swaying in a current, or a bobtail squid darting around, is basically impossible to focus on.

[Interceptor121 719]

2 hours ago, Architeuthis said:

I start to decide which mirrorless FF system to acquire and ask for help. At present, no system offers a complete set of lenses for UW with the corresponding mirrorless mount. While I think that adapted DSLR fisheye lenses (except Nikon where some DSLR lenses do not work properly, even with native Nikon adapter) will not be a problem at all, macro lenses with focal length around 100mm certainly may be. This will be an important factor for decision making. There are plenty of reports/reviews of a single lens existing, but what is fast and accurate, is certainly a subjective statement, especially when there is no practical experience with other systems and therefore no comparison...

Therefore I would greatly appreciate if UW photographers that have practical experience with more than one macro setup could state, how they would rate AF speed/accuracy (and eventually also other relevant features) of the different system configurations in comparison (and maybe relate to more common setups as e.g. Oly EM1II with Zuiko 60mm macro (this is what I personally have at present) and/or Nikon 105 mm macro on D8xx):

 

#1.: Sony A7RIV (or RIII) with:

Sony 90mm macro, native E-mount

Sigma 105mm macro, native Sony E-mount

Canon 100mm IS macro, adapted via MC11to Sony E-mount

=> While Sony seems to be the most mature mirrorless FF system at present, there are several reviews and reports by users here, that state AF speed of the Sony mount macros is very slow. I found a remarkable statement by Backscatter's Jim Decker, regarding the A7RIV: "For macro, the Canon 100mm IS macro lens with the Sigma MC-11 Mount Converter focuses much faster than the native Sony 90mm macro. ...": https://www.backscatter.com/reviews/post/Sony-a7R-IV-Underwater-Camera-Review

Can this be real and if yes, how is performance of Canon 100mm IS on A7RIV compared to the same lens on a Canon R body???

 

#2.: Canon R5, R6 or R with:

Canon 100mm macro, EF-mount adapted with Canon adapter

Canon 85mm macro, native RF mount

 

Thanks, Wolfgang

 

When you look at how focus systems are defined you need to understand how the camera achieves focus

Most cameras achieve focus with the lens wide open and the close the aperture when they need to shoot.

This means that if you are shooting macro you are effectively at f/2.8 with typically a fast shutter speed say 1/250.

This is a scene that has an exposure value of 11 EV at ISO 100 or 5120 lux in essence a sunny day.

Your camera will typically have a -Ev rating for single AF (forget about tracking) which is usually something like -4.5 Ev 

In our case 11-4.5=6.5 the camera will refuse to focus at less than 226 lux which is not that dark after all. Increasing gain (ISO) does not change the camera ability to focus but helps you seeing the LCD and focus manually

Looking at your examples 

Sony A7R4 EV -3

Canon R5 Ev -6 

The canon R5 has 3 stops benefit

For reference

Nikon D500 -4 EV

Panasonic S5 -6 EV

Nikon Z7II -4 EV

So Canon and Panasonic have an edge on Nikon/Sony probably due to the different nature of the autofocus system. Adapted lenses do not perform as well as native

 

 

Edited March 2, 2021 by Interceptor121

[ChrisRoss 150]

6 hours ago, Interceptor121 said:

This is a scene that has an exposure value of 11 EV at ISO 100 or 5120 lux in essence a sunny day.

Your camera will typically have a -Ev rating for single AF (forget about tracking) which is usually something like -4.5 Ev 

In our case 11-4.5=6.5 the camera will refuse to focus at less than 226 lux which is not that dark after all. Increasing gain (ISO) does not change the camera ability to focus but helps you seeing the LCD and focus manually 

 

The equation I think should be:  11 - (-4.5) = 15.5.

That aside the EV value indicates how dark it can still focus at, but is probably not the full story, some lens/camera combinations are just not as well tuned for AF, no matter the light.  The EM-1 MkII is apparently rated at -6EV with the latest firmware.  This fits with my experience, I was shooting Mandarin fish at Lembeh at 6m depth at dusk, I could still see without a torch, but it was dim.  The fish didn't like my focus light so I turned it off and found the camera had no problem focusing. 

Out of the pack of FF options I would think Canon might be your choice, -6EV AF, you already own the 8-15 fisheye and AF is not going to be an issue with that.  The only missing parameter is the macro lens.  I think you could get a good feel for the AF performance if you went to a bricks and mortar store to try out the camera indoors with the various macro options, seeing how it performs at around 1:1.

The problem with deciding based on advice here is that the issue is so subjective and you don't know the other person's criteria or even if they have tried the better option or not.  They may have only used a older style mirrorless AF option and not tried a DSLR and perhaps don't know how good it can get?

[Interceptor121 719]

The equation I think should be:  11 - (-4.5) = 15.5.
That aside the EV value indicates how dark it can still focus at, but is probably not the full story, some lens/camera combinations are just not as well tuned for AF, no matter the light.  The EM-1 MkII is apparently rated at -6EV with the latest firmware.  This fits with my experience, I was shooting Mandarin fish at Lembeh at 6m depth at dusk, I could still see without a torch, but it was dim.  The fish didn't like my focus light so I turned it off and found the camera had no problem focusing. 
Out of the pack of FF options I would think Canon might be your choice, -6EV AF, you already own the 8-15 fisheye and AF is not going to be an issue with that.  The only missing parameter is the macro lens.  I think you could get a good feel for the AF performance if you went to a bricks and mortar store to try out the camera indoors with the various macro options, seeing how it performs at around 1:1.
The problem with deciding based on advice here is that the issue is so subjective and you don't know the other person's criteria or even if they have tried the better option or not.  They may have only used a older style mirrorless AF option and not tried a DSLR and perhaps don't know how good it can get?

No it doesn’t work that way the lowest ev is a negative value and the ev are always added.
So the range is 11ev + the range so this results in an offset. Say it was 20 to -4 it becomes 31 to 7 ev. Other than the math this is a CIPA test on single AF which maybe is not what you use anyway
The negative value is a good proxy for that however performance in continuous mode falls apart much sooner.
Cameras employ then other tricks like reducing the shutter speed and therefore the frame rate of your evf to try and focus this generally kills entirely the continuous autofocus that needs high refresh rates
All considered the negative ev mentioned remains your only point of reference
In general all mirrorless camera switch to contrast detect in low light and the different performance shows how well or how bad they cope in those conditions that are typically different from the normal operating conditions
The only real way to see if does or not apply to your use case is a test obviously


Sent from my iPhone using Tapatalk

[hyp 104]

I thought the question was about macro stills photography. It’s not low light! And if it really is bring a focus light (preferably with red colour mode). 

[ChrisRoss 150]

2 hours ago, hyp said:

I thought the question was about macro stills photography. It’s not low light! And if it really is bring a focus light (preferably with red colour mode). 

moving off topic a little - using the AF sensitivity as a proxy for good macro AF but as I pointed out it's more than just how sensitive the AF is in low light.  Some lenses have better AF than others and some bodies will AF better with the same lens.  The focus light will help somewhat but some macro lenses are just slow. 

 

[Interceptor121 719]

4 hours ago, hyp said:

I thought the question was about macro stills photography. It’s not low light! And if it really is bring a focus light (preferably with red colour mode). 

Macro photography is low light by definition as you use small aperture fast shutter and low ISO

If you put a focus light in the mix any camera can focus easily all the ideas you need tracking for macro etc for me are more wishful thinking and a proxy for the diver not the subject moving

[hyp 104]

I guess low light is a question of Definition then. Personally, I think it's low light, when it's dark. Examples would be Mandarin Dives at Dusk, where you can't have artificial light. Also some dive spots with low visibility and deep depth will be pretty dark. 

As far as I know, cameras AF with open Apertures so the maximum Aperture determines how much light is available for the AF system. It doesn't really matter if you close down the aperture for DoF. This is maybe different for Video. 

I know that you think that tracking is overrated and unnecessary , but it has been quite clear to me that a number of people on Wetpixel seem to enjoy putting a Focus Point on a subject and having it stick there no matter who moves. I don't own a camera modern enough to have access to this technology, so in part I agree with your assessment that it's unnecessary, but it sure sounds nice. I'm also fairly sure that @Architeuthis shoots that way from previous posts he's made. 

Telling people that a feature they inquire about is useless is really not all that helpful in their search for answers. Especially when he was quite specific in asking for real world experience. The Specsheets from manufacturers are there for all of us to google.

[Interceptor121 719]

46 minutes ago, hyp said:

I guess low light is a question of Definition then. Personally, I think it's low light, when it's dark. Examples would be Mandarin Dives at Dusk, where you can't have artificial light. Also some dive spots with low visibility and deep depth will be pretty dark. 

As far as I know, cameras AF with open Apertures so the maximum Aperture determines how much light is available for the AF system. It doesn't really matter if you close down the aperture for DoF. This is maybe different for Video. 

I know that you think that tracking is overrated and unnecessary , but it has been quite clear to me that a number of people on Wetpixel seem to enjoy putting a Focus Point on a subject and having it stick there no matter who moves. I don't own a camera modern enough to have access to this technology, so in part I agree with your assessment that it's unnecessary, but it sure sounds nice. I'm also fairly sure that @Architeuthis shoots that way from previous posts he's made. 

Telling people that a feature they inquire about is useless is really not all that helpful in their search for answers. Especially when he was quite specific in asking for real world experience. The Specsheets from manufacturers are there for all of us to google.

Because you are using the camera at negative exposure numbers (most cameras AF refuses to work when the exposure meter is below -3 unless you are in manual focus) you are effectively in low light. The example that I provided is based already on wide aperture and goes to show that even at f/2.8 1/250 a typical macro shot the camera is expecting a level of brightness much higher of what it gets underwater. So the ability to focus in low light in fact matters because you are not exposing for middle grey as you use your flash to provide light

This may be difficult to understand but this is the reason why cameras fail to focus underwater. If all was bright you may occasionally focus on something that is not what you wanted but rest assured the camera will focus. Try some garden macro and see it for yourself.

With regards to tracking as a proxy of the diver moving this is resolved by the diver NOT moving not by the camera tracking. I know some people rely on those features but those are designed for the camera to be fixed and the subject to be moving as they are based on motion prediction so something has to be still relative to the other. The Olympus tracking Wolfgang mentions on land on a bright scene is mediocre at best. I would really like to see the hit rate of this shots. Nobody shooting a bird uses tracking today

Cameras are moving in the direction of subject detection (i.e. identifying what is the subject in the frame) to then focus on it. This method has got the highest success rate. Unfortunately fish are not an animal the camera will detect

The traditional tracking with motion vector on a mirrorless camera requires analysis of the frame which means it is operating exactly like in video mode.  In the above f/2.8 example assuming a frame rate of 30 fps we are looking still at 9 EV which is still very very bright and nowhere near an underwater situation UNLESS you have a focus light.

A modest focus light with a narrow beam of 60 degrees and 180 lumens at 1 foot provides 2292 Lux which is 9.8 Ev at that point the camera will be very happy to focus track and do whatever it needs to do

Once light is provided almost any camera on the market can do the tracking job or any continuous autofocus

A comparison like the op requested does not exist and it will not exist until someone goes in a pool and scientifically tries all those camera under constant illumination. Nobody does those things in the world of underwater photography so we are here to discuss things at libitum

However who understands the mechanics of a camera usually takes the right decision in less time and ends up with all the shots in focus.

 

[hyp 104]

Most people underwater are not still. Which is why they like tracking. You can say that being still is better, but that argues besides reality. It also has nothing to do with tracking fast birds. Anyway, I'm out. There are no points for being right on the internet.

[Interceptor121 719]

43 minutes ago, hyp said:

Most people underwater are not still. Which is why they like tracking. You can say that being still is better, but that argues besides reality. It also has nothing to do with tracking fast birds. Anyway, I'm out. There are no points for being right on the internet.

Tracking works on the assumption that the frame is still and the object moves. It is called motion prediction. If the frame moves and as result the subject moves tracking fails you can see this yourself on land swaying the camera while you point at something.

Some systems like Nikon 3D tracking (which works differently from mirrorless tracking) are effective in the 'swaying' mode. Is almost the only one the others all fail miserably

[Barmaglot 230]

4 hours ago, Interceptor121 said:

Macro photography is low light by definition as you use small aperture fast shutter and low ISO

I don't know about other cameras, but mine keeps the aperture fully open while focusing, stopping down to set value when it's ready to take a shot. The actual shot is done with strobes, so it's got all the light it needs.

[Interceptor121 719]

51 minutes ago, Barmaglot said:

I don't know about other cameras, but mine keeps the aperture fully open while focusing, stopping down to set value when it's ready to take a shot. The actual shot is done with strobes, so it's got all the light it needs.

read it again. Even with your lens fully open at f2.8 the EV of the scene is 11 which corresponds to 2200 lux this is more that you get on a surgeon table. Your camera has to focus before your strobes fire.

So there is not plenty of light if there was focus lights would not be needed would they?

I realise most people do not actually understand why cameras have issues underwater by reading the answers I get in this post

Anyway as I actually don't need or use tracking either on land or underwater I leave it to you the experts to wonder why your cameras do not focus!

Edited March 3, 2021 by Interceptor121

[Phil Rudin 446]

On 3/2/2021 at 9:15 AM, Architeuthis said:

I start to decide which mirrorless FF system to acquire and ask for help. At present, no system offers a complete set of lenses for UW with the corresponding mirrorless mount. While I think that adapted DSLR fisheye lenses (except Nikon where some DSLR lenses do not work properly, even with native Nikon adapter) will not be a problem at all, macro lenses with focal length around 100mm certainly may be. This will be an important factor for decision making. There are plenty of reports/reviews of a single lens existing, but what is fast and accurate, is certainly a subjective statement, especially when there is no practical experience with other systems and therefore no comparison...

Therefore I would greatly appreciate if UW photographers that have practical experience with more than one macro setup could state, how they would rate AF speed/accuracy (and eventually also other relevant features) of the different system configurations in comparison (and maybe relate to more common setups as e.g. Oly EM1II with Zuiko 60mm macro (this is what I personally have at present) and/or Nikon 105 mm macro on D8xx):

 

#1.: Sony A7RIV (or RIII) with:

Sony 90mm macro, native E-mount

Sigma 105mm macro, native Sony E-mount

Canon 100mm IS macro, adapted via MC11to Sony E-mount

=> While Sony seems to be the most mature mirrorless FF system at present, there are several reviews and reports by users here, that state AF speed of the Sony mount macros is very slow. I found a remarkable statement by Backscatter's Jim Decker, regarding the A7RIV: "For macro, the Canon 100mm IS macro lens with the Sigma MC-11 Mount Converter focuses much faster than the native Sony 90mm macro. ...": https://www.backscatter.com/reviews/post/Sony-a7R-IV-Underwater-Camera-Review

Can this be real and if yes, how is performance of Canon 100mm IS on A7RIV compared to the same lens on a Canon R body???

 

#2.: Canon R5, R6 or R with:

Canon 100mm macro, EF-mount adapted with Canon adapter

Canon 85mm macro, native RF mount

 

Thanks, Wolfgang

 

Hi Wolfgang, To respond to your original post I have used I have used all of the Sony A7 series cameras from A7 II on up and including the A7R IV and new A7C. I have also used the Canon ESO R but not the newer R 5 & 6. I have also used the 90mm macro and Canon macro with the adapter on the latest Sony cameras and to me the native Sony lens is faster and more accurate than the Canon combination. I read the Backscatter review and I respect Jim Decker and his findings. The problem is that the Sony AF system can be complex to dial in and not all of use set it up the same way so AF results can very. I have also used the Canon 100M with adapter on Canon with mixed results. Canon"s AF has greatly improved since my EOS R test in 2019. Regarding the Sigma I tired out the 70mm macro and it was lacking in several ways, speed, extension (not able to fit in a macro port) and more. While I have not tested the Sigma 105mm macro the company CEO has stated that they placed the emphasis on IQ rather than speed, so I would expect it to be slower. While the Canon RF 85mm F/2 macro is a reasonably priced and fastens,  it lacks the full 1:1 life size and is a 1:2 lens. This may very well work for many but most full frame macro shooters will prefer the 1:1.    

[Interceptor121 719]

Phil Rudin makes a good point as usual. Lenses motor and precision are important 

The sigma 105mm produces very nice images but is very slow

https://www.lenstip.com/lenses_reviews.html has most lens reviews for emount and other mounts and is usually very reliable

[Phil Rudin 446]

While I agree with 121 that lots of useful info can be found in reviews you need to read them thoroughly. I this case of lenstip while the Sony FE 90mm lens has excellent image quality they say the lens is slow, seems I have heard that somewhere else before. That is because it was tested on a Sony A7R II camera. We all agree that the lens on that camera was slow. 

 

[Interceptor121 719]

1 hour ago, Phil Rudin said:

While I agree with 121 that lots of useful info can be found in reviews you need to read them thoroughly. I this case of lenstip while the Sony FE 90mm lens has excellent image quality they say the lens is slow, seems I have heard that somewhere else before. That is because it was tested on a Sony A7R II camera. We all agree that the lens on that camera was slow. 

 

They use the same camera for all the lenses test so that when they say it is slow it means it is slower compared to other sony mount

So this is useful to assess lenses on a format. In our case the op wants to compare across formats this is much more difficult to do and there is no reference data handy

Edited March 3, 2021 by Interceptor121

[Barmaglot 230]

9 hours ago, Interceptor121 said:

read it again. Even with your lens fully open at f2.8 the EV of the scene is 11 which corresponds to 2200 lux this is more that you get on a surgeon table. Your camera has to focus before your strobes fire.

Again, I was responding to this:

13 hours ago, Interceptor121 said:

Macro photography is low light by definition as you use small aperture fast shutter and low ISO

Low light, small aperture and low ISO are things that happen, but they don't happen together. While the camera is focusing, it's using a wide aperture and high ISO, and while it's taking the photo, it's firing strobes which provide all the light it would ever need.

To reiterate - with a mirrorless camera that is five year old now (Sony A6300) and the much-maligned (in reviews) SEL90M28G lens, the only things that give me trouble focusing are:

• Small subjects that quickly move across large distances - for example, a nudibranch on a hydroid that's swaying in a current
• My own movement (current, surge, etc)
• Truly impressive amounts of particles in the water (like, trouble seeing my own hands)
• Small translucent subjects against a moderately distant (30-50cm) busy background - sometimes the camera decides to focus on that background and ignore the subject.

Overall, I'm quite happy with this camera/lens combination, and a newer body with the latest autofocus tech in it should perform even better.

[ChrisRoss 150]

Massimo, all this may be your experience, but using my EM-1 II underwater, it doesn't behave like suggested above.  it will focus at very low light levels, last night I tried focusing on my keyboard at home, I used my incident meter to measure illuminance and I was getting readings in the range 30-50 lux and at around 1:2 magnification  with the 60mm macro it could focus on the keys.    I tried another surface a bit further from my screen which was 15-20 lux, it wouldn't focus closeup but if I backed off a bit to about 500mm away to lower the magnification it would focus.   Macro lenses typically get harder to AF as you move towards 1:1, there is light loss due to magnification even with modern designs but magnification by  itself seems to play a part.

I used it with my 12-40 f2.8 lens at Lembeh with Mandarin fish 6m down at dusk, enough light to see but very dim and it focused on the fish successfully without a focus light.  During daylight hours even if it's overcast it will focus reliably on critters on the sponge reefs at a depth of about 10-15m and only moderate vis of a few m so it's relatively dark. 

I also use tracking it's invaluable to me as more often than not the dive sites I dive have some level of surge so both the diver and the subject are moving a little due to the surge.

 

[Interceptor121 719]

Massimo, all this may be your experience, but using my EM-1 II underwater, it doesn't behave like suggested above.  it will focus at very low light levels, last night I tried focusing on my keyboard at home, I used my incident meter to measure illuminance and I was getting readings in the range 30-50 lux and at around 1:2 magnification  with the 60mm macro it could focus on the keys.    I tried another surface a bit further from my screen which was 15-20 lux, it wouldn't focus closeup but if I backed off a bit to about 500mm away to lower the magnification it would focus.   Macro lenses typically get harder to AF as you move towards 1:1, there is light loss due to magnification even with modern designs but magnification by  itself seems to play a part.
I used it with my 12-40 f2.8 lens at Lembeh with Mandarin fish 6m down at dusk, enough light to see but very dim and it focused on the fish successfully without a focus light.  During daylight hours even if it's overcast it will focus reliably on critters on the sponge reefs at a depth of about 10-15m and only moderate vis of a few m so it's relatively dark. 
I also use tracking it's invaluable to me as more often than not the dive sites I dive have some level of surge so both the diver and the subject are moving a little due to the surge.
 

30 lux is not low light level and is around 4 EV in fact
If the claims of -6 ev of olympus were true it would focus at 0.04 lux
This is single AF
In tracking AF the value reported drops because the camera is analysing frames and can only do that processing video
So the tracking drops much sooner than your example cameras resort to tricks to compensate increasing gain but this eventually comes to an end
So the performance of tracking and single or continuous AF is not the same
At f2.8 1/30 (refresh used to interpolate video frames) you would need 588 lux for it to work at ISO 100 the camera increase gain so that it can see it but this increases noise and makes the tracking likely to fail
This is way in low light cameras only focus in single AF
Try it yourself with C-AF-tracking (which misses a lot also in bright light)


Sent from my iPhone using Tapatalk

[Interceptor121 719]

Low light, small aperture and low ISO are things that happen, but they don't happen together. While the camera is focusing, it's using a wide aperture and high ISO, and while it's taking the photo, it's firing strobes which provide all the light it would ever need.
To reiterate - with a mirrorless camera that is five year old now (Sony A6300) and the much-maligned (in reviews) SEL90M28G lens, the only things that give me trouble focusing are:

• Small subjects that quickly move across large distances - for example, a nudibranch on a hydroid that's swaying in a current
• My own movement (current, surge, etc)
• Truly impressive amounts of particles in the water (like, trouble seeing my own hands)
• Small translucent subjects against a moderately distant (30-50cm) busy background - sometimes the camera decides to focus on that background and ignore the subject.

Overall, I'm quite happy with this camera/lens combination, and a newer body with the latest autofocus tech in it should perform even better.

Yes that’s what I wrote the camera is focussing with lens wide open but increasing gain ISO increases noise which in turn makes the camera fail sooner when you engage tracking that uses live view not a single AF read
I have no issues with my camera focus most of the times the reason I use manual focus is to make sure the macro lens is at maximum magnification
If you use autofocus you don’t know if you got close enough until it fails
For me the autofocus story is mostly a hype but if someone wanted to compare you need to look at the combination of camera lens and situation


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[ChrisRoss 150]

1 hour ago, Interceptor121 said:

30 lux is not low light level and is around 4 EV in fact
If the claims of -6 ev of olympus were true it would focus at 0.04 lux
This is single AF
In tracking AF the value reported drops because the camera is analysing frames and can only do that processing video
So the tracking drops much sooner than your example cameras resort to tricks to compensate increasing gain but this eventually comes to an end
So the performance of tracking and single or continuous AF is not the same
At f2.8 1/30 (refresh used to interpolate video frames) you would need 588 lux for it to work at ISO 100 the camera increase gain so that it can see it but this increases noise and makes the tracking likely to fail
This is way in low light cameras only focus in single AF
Try it yourself with C-AF-tracking (which misses a lot also in bright light)


Sent from my iPhone using Tapatalk

It was C-AF plus tracking - I always use it. and you did say :  "In our case 11-4.5=6.5 the camera will refuse to focus at less than 226 lux which is not that dark after all. "  which to me read a -4.5EV rated AF sensitivity camera won't focus at 226 lux or lower - I may have interpreted that wrong - but it prompted me to quote my camera focusing at 30 lux.

While I was playing around I swapped the 60mm macro to the 12-40 f2.8 and it was far quicker to focus - even two different f2.8 lenses respond differently.   You may find that the Olympus can only AF at -6 EV with an f1.2 prime lens at low magnification and only with a" good tailwind "

[Interceptor121 719]

24 minutes ago, ChrisRoss said:

It was C-AF plus tracking - I always use it. and you did say :  "In our case 11-4.5=6.5 the camera will refuse to focus at less than 226 lux which is not that dark after all. "  which to me read a -4.5EV rated AF sensitivity camera won't focus at 226 lux or lower - I may have interpreted that wrong - but it prompted me to quote my camera focusing at 30 lux.

While I was playing around I swapped the 60mm macro to the 12-40 f2.8 and it was far quicker to focus - even two different f2.8 lenses respond differently.   You may find that the Olympus can only AF at -6 EV with an f1.2 prime lens at low magnification and only with a" good tailwind "

Yes Olympus specs are for 1.2 prime lens at not very long end so when you look at 2.8 you are at the -4.5 Ev of anybody else in single AF

Tracking uses motion vector estimation https://en.wikipedia.org/wiki/Motion_estimation this requires processing of entire frames not just a contrast point which in turns means the camera needs to have full video frames processed to analyse to see if it has lost the plot or not. This in turn means the level of light required are increased.

In the mix goes also how fast the lens is to achieve focus. Some lenses like the Olympus 60mm are pretty bad and they have a lot of breathing when you focus. So if you focus it first and then stay around that area it works much better. But the performance compared to a standard zoom lens even at the same aperture is just terrible

The ability of the camera to work at low level of illumination together with the ability of the lens to focus quickly determine how effective it is underwater. So going back to the op question assuming the test is performed with lenses of similar aperture (generally this is 2.8 for full frame not less or they may not focus at all) a camera with a rating of -6 Ev will work better than one with -3 Ev which is where this started as a starting point. Then you need to overlay focus speed and accuracy that has also to do with the lens.

For tracking there is an additional dimension which is the quality of the motion vector estimation which depends on the processing quality and power of the camera.

Sony for example has very good record of tracking in daylight but at the same time a pretty bad reputation of not focussing at all in low light and being slow with macro lenses.

If you add a focus light in the mix (obviously this is important because a lot of macro is inside crannies where there is no light and you are much lower than your desk) almost all cameras can focus (eventually) at the focus speed of the system.

I would be a bit calm before saying that underwater there is plenty of light there is not. A nudibranch on a rock sitting flat with light hitting it is not the same as trying to shoot a seahorse on a fan at an angle where light is not reflecting.

So if I had to look at performance of a lens for macro I look at the following dimensions

1. Camera ability to focus in low light (most cameras are rated -4 Ev and lower and I would say away from anything that says -3 or -2 Ev)

2. Lens time to scan for focus. Before you can even think of engaging tracking you need to pre-focus and that first operation is critical so you can continue

I do not look at how good the camera is at motion estimation and this is not a published stat so there is no way to read something and see if this camera will be better than another at tracking

Going back to @Architeuthis question. I use the MC21 adapter and metabones like he does. With adapted lenses only Single AF works reliably so tracking is not available. The two criteria above hold.

The Sony camera rating of -3 Ev is not convincing for me

Among Canon R5, R6 and R the rating is respectively -6, -6.5, -6 but obviously the R6 has a lower megapixel count 

Having discounted adapted lens if you wanted CAF or tracking you are left with the Canon 85 mm f/2 which is not known to be particularly fast.

The reality is that DSLR in this area is still way ahead when it comes to focus speed as the lenses focus really fast.

It would be worth to find someone that has tested the Canon RF 85 AND the Sony 90mm to see in real life how those work I would avoid any adapted lens for macro. Perhaps the Sony lens is better than canon and makes up for the camera being less able or you dive with a focus light and you are done with it. 

I would not invest on a system if there are no native lenses as adapted lenses are always a compromise you can take for wide angle but not for macro in my experience.

Hopefully this last post helps Wolfgang making up his mind

 

[Architeuthis 140]

17 hours ago, Phil Rudin said:

Hi Wolfgang, To respond to your original post I have used I have used all of the Sony A7 series cameras from A7 II on up and including the A7R IV and new A7C. I have also used the Canon ESO R but not the newer R 5 & 6. I have also used the 90mm macro and Canon macro with the adapter on the latest Sony cameras and to me the native Sony lens is faster and more accurate than the Canon combination. I read the Backscatter review and I respect Jim Decker and his findings. The problem is that the Sony AF system can be complex to dial in and not all of use set it up the same way so AF results can very. I have also used the Canon 100M with adapter on Canon with mixed results. Canon"s AF has greatly improved since my EOS R test in 2019. Regarding the Sigma I tired out the 70mm macro and it was lacking in several ways, speed, extension (not able to fit in a macro port) and more. While I have not tested the Sigma 105mm macro the company CEO has stated that they placed the emphasis on IQ rather than speed, so I would expect it to be slower. While the Canon RF 85mm F/2 macro is a reasonably priced and fastens,  it lacks the full 1:1 life size and is a 1:2 lens. This may very well work for many but most full frame macro shooters will prefer the 1:1.    

Precious information from someone who has practical experience with many different systems - thanks a lot Phil!

I have the impression that Sony offers at present a lot of advantage (size, IQ, price), would there not be the controversial issue with macro, therefore I am eager to hear as many opinions as possible, before I decide...

Since you have a lot of experience with EM1II (that I have now), may I ask you to compare AF with the Sony 90mm macro on R7iv (7c) with the EM1II and Zuiko 60mm (Panasonic 45mm macro may be even more appropriate. One may say also that the Sony 90mm should have an additional diopter to give 2:1 to be really comparable with Pana 45mm at 1:1). This would give me a reference feeling how AF works with the Sony...

What regards my personal experience, S-AF with Pana 45mm on EM5II (CAF) was good, but Zuiko 60mm a little cumbersome (when I just had EM5II, I did not regard S-AF with Zuiko 60mm cumbersome). Since I have EM1II (PDAF), C-AF, both with 45mm and 60mm is the method I prefer, not th eleast issue with 45mm, with Zuiko 60mm (probably depending on light), sometimes I have to try several times until C-AF is maintained during reframing. The example picture was (even) taken with Canon 100mm IS macro, adapted with metabones 0.71x (so 71mm in fact), C-AF to the eye and then reframing (but this really is the limit of the system, AF with the adapted 100mm is really cumbersome...):

 

Wolfgang

Edited March 4, 2021 by Architeuthis