low light AF frustration wth a nex F3

I love my little nex F3 (my second camera) for it's image quality but its autofocus indoors / lowlight is driving me crazy.

Using flexible spot it can hunt / it is slow when contrast is just dropping a bit. When nearby background has more contrast it just locks on the background. From time to time I even have to rely on manual focussing.

With my PDAF DSLR camera I never have these kind of issues.

Are the more expensive nex models with PDAF a lot better in these regard, or even the latest m43 camera's?

sonics said:

I love my little nex F3 (my second camera) for it's image quality but its autofocus indoors / lowlight is driving me crazy.

Using flexible spot it can hunt / it is slow when contrast is just dropping a bit. When nearby background has more contrast it just locks on the background. From time to time I even have to rely on manual focussing.

With my PDAF DSLR camera I never have these kind of issues.

Are the more expensive nex models with PDAF a lot better in these regard, or even the latest m43 camera's?

Click to expand...

I have the Nex-5N and Nex-7, both of which do not have PDAF. If you want an improvement, stay away from these two cameras. It dose the exact same thing you described in low light, and focusing in low light can really be a pain in the ass sometimes.

One trick I use is to focus at something of similar distance, but with much more contrast, to bring the focus in range, then try to focus on the problem area again. If that doesn't work I switch to MF.

Hopefully owners of the newer NEXes can help out out with this.

--
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sonics said:

I love my little nex F3 (my second camera) for it's image quality but its autofocus indoors / lowlight is driving me crazy.

Using flexible spot it can hunt / it is slow when contrast is just dropping a bit. When nearby background has more contrast it just locks on the background. From time to time I even have to rely on manual focussing.

With my PDAF DSLR camera I never have these kind of issues.

Are the more expensive nex models with PDAF a lot better in these regard, or even the latest m43 camera's?

Click to expand...

Contrast detecting cameras all suffer from low contrast when used indoors or under lowlight, even the m43 cameras. Upgrading to PDAF does not really help - you need to increase the contrast level on the subject.

Easiest is to get a faster lens - e.g. the 35mm f/1.8 compares to the kit lens at 35mm f/4.5. That is, about 2.5 stops difference, which is a lot of light. You'll notice that the F3 with the faster lens will focus a lot easier under the same conditions.

The faster lens does not solve the background focus issue when the background has higher contrast levels than your subject. If this is the case, use MF or DMF.

As to using the kit lens indoors or under lowlight, aside the focus hunting or not finding focus, and the poor LCD display (grainy), the images will be respectable none-the-less. Still, a faster lens will result in a more rewarding experience with more pleasing pictures, I am sure. I never use the kit lenses indoors or under low light anymore.

The PDAF level Nex cameras use the PDAF algorithm to 'pick a focus area', and then complete fine AF using the CDAF. This can still result in background focus. DSLR based cameras use PDAF to measure the distance to subject (precisely) and then tell the lens where to focus. Both Nex and DLSR camera need sufficient contrast for PDAF to work as well, and to do the measurements, but think of the Nex PDAF as a course grain guidance whereas the DLSR PDAF is a fine grain measure.

The new A7/r cameras seem to generally do better because of (a lot) more compute power in the CDAF processing engine, allowing more 'heuristics' to be applied. They focus very fast.

The m43 cameras seem to combine more compute power with more advanced algorithms, resulting also in faster focusing than Nex cameras do. A give here may be that, under same exposure, the DOF on the m43 is deeper, resulting in less CDAF measurements that need to be taken to control lens movement, hence faster focusing.

On a Nex camera, you can notice that AF lenses with shallow DOF (E50) focus slower than lenses with larger DOF (E35, E1650).

Depending on the lens, I can get OK results from Nex 6, but it doesn't really have DSLR like night focusing ability yet - I was able to acquire focus in near darkness with my Canon (but then, the high ISO wasn't that good). Also with PDAF you get faster focus but also back and front focusing issues... it's a trade-off.

As I said it's also very lens dependent. In really dim conditions (e.g. a glowstick birthday party with lights basically off) any lens will struggle. In "normal" dim conditions, e.g. a poorly lit karate dojo, I am getting good results with Sigma 30/2.8, but the faster Sony 50/1.8 suffers from slow and hunting AF. The biggest problem is using a long tele in poor light, as there's really just one E mount option.

And to add, I am using manual focusing whenever I can anyway, it's the only way to achieve critical focus 100%, DSLR or not. I would use Live View on my T3i for critical portrait shots, and the Nex is so much better in this respect.

If you are shooting in the such low light that you can't get AF on anything then use MF instead with focus peaking or buy a faster lens. Otherwise stick to you Canon equipment which is what you prefer by looking at your post history.

Try turning off the focus assist light, if it doesn't illuminate your target it actually makes focus worse, and often it gets blocked by the lens or hood.

Secondly, contrast detect focus is about contrast (a well defined edge). They can focus in low light as long as there is contrast.

• Turn off AF Assist Light
• Turn subject so light is creating contrast on their front (be sure there is a light off to one side shining across the face)
• Set the focus to Flexible Spot (where you can choose the focus point)
• Put the focus point on the highest contrast (vertical line sensitive), be sure focus point doesn't overlap the background. For a person this is usually the chest or eyes (as long as light is reflecting off eye).

My main complaint with NEX is you can't change the focus point size to prevent it from overlapping the background or making it larger to ensure it has and edge to see, so you have to be aware of this limitation and work around it by not having focus point overlap background.

One of the biggest complaints I notice too is that if you put the focus point on the face, if your subject is back lit the camera will often focus on the hair in line with the ears since the light is making it nice and high contrast. This makes the eyes a bit soft. This is mostly with the 50mm f/1.8. With the kit lens it probably won't be noticeable.

It sounds like a lot of work, but it isn't.

Eric

The 50mm f/1.8 lens is an oddball - it has a nice fast aperture and a slow focusing action - i like mine but it takes a bit of understanding.

I also have an F3 with the 1855 kit. I have switched to manual focus all the time. With focus peaking and magnified view, it works quickly and well. However, I am not overwhelmed with the focusing accuracy, even when focusing manually. Maybe it's due to sharpness limitations of the lens. I am thinking about getting one of the Sigma lenses, since from what I read on this forum these are quite sharp. Any thoughts about which of them to get as a useful walk around lens?

The 18-55 is a pretty sharp lens and you should be getting nice sharp shots from it - of course the Sigma primes will be better in many situations - choose the one which has a focal length you will use.




NEXF3 and 18-55 kit lens.

LoneReaction said:

I have the Nex-5N and Nex-7, both of which do not have PDAF. If you want an improvement, stay away from these two cameras. It dose the exact same thing you described in low light, and focusing in low light can really be a pain in the ass sometimes.

Click to expand...

Not true and there is very little difference between the AF speed between the NEX cameras with hybrid PDAF/CDAF compared to the 5n or 7. Numerous articles and DPReview posts have addressed this but it's really a minor difference.

http://www.snicolphotos.com/blog/2013/2/is-the-new-hybrid-af-system-on-the-nex-6-actually-any-faster

Sony gave us the CDAF/PDAF hybrid to appease those complaining about focus speed since so many articles were exaggerating DSLR PDAF capabilities and the perception that mirrorless/CDAF is awful. In reality CDAF is more accurate and PDAF hybrid is slightly faster. You're not going to get good low light focus capabilities on any camera with a slow lens. If Sony wanted to they could have put faster lenses on the NEX cameras but they would have been bigger and more expensive. If you doubt this, search on DSLR slow AF focus and see all the results for Nikon and Canon which have slow kit lenses as well with the max aperture of F3.5. Buy a 35mm 1.8 or 50mm 1.8 if you are going to shoot in very low light. Better yet, use the flash in very low light situations. In moderate lighting, I think the NEX cameras do well at night even with kit lenses. Using the AF illumination helps too if you're having problems locking focus. Another good option is hand held twilight scene mode.

viking79 said:

One of the biggest complaints I notice too is that if you put the focus point on the face, if your subject is back lit the camera will often focus on the hair in line with the ears since the light is making it nice and high contrast. This makes the eyes a bit soft. This is mostly with the 50mm f/1.8. With the kit lens it probably won't be noticeable.

It sounds like a lot of work, but it isn't.

Eric

Click to expand...

Face detection works well in the situation you're describing above but you are stuck with multi-focus area setting. I do wish face detection worked on dogs/cats. Ha. Direct Manual Focus (DMF) works well for me and I double check and adjust the AF focus by turning the focus ring while shutter is halfway depressed.

PVCdroid said:

LoneReaction said:

I have the Nex-5N and Nex-7, both of which do not have PDAF. If you want an improvement, stay away from these two cameras. It dose the exact same thing you described in low light, and focusing in low light can really be a pain in the ass sometimes.

Click to expand...

Not true and there is very little difference between the AF speed between the NEX cameras with hybrid PDAF/CDAF compared to the 5n or 7. Numerous articles and DPReview posts have addressed this but it's really a minor difference.

http://www.snicolphotos.com/blog/2013/2/is-the-new-hybrid-af-system-on-the-nex-6-actually-any-faster

Sony gave us the CDAF/PDAF hybrid to appease those complaining about focus speed since so many articles were exaggerating DSLR PDAF capabilities and the perception that mirrorless/CDAF is awful. In reality CDAF is more accurate and PDAF hybrid is slightly faster. You're not going to get good low light focus capabilities on any camera with a slow lens. If Sony wanted to they could have put faster lenses on the NEX cameras but they would have been bigger and more expensive. If you doubt this, search on DSLR slow AF focus and see all the results for Nikon and Canon which have slow kit lenses as well with the max aperture of F3.5. Buy a 35mm 1.8 or 50mm 1.8 if you are going to shoot in very low light. Better yet, use the flash in very low light situations. In moderate lighting, I think the NEX cameras do well at night even with kit lenses. Using the AF illumination helps too if you're having problems locking focus. Another good option is hand held twilight scene mode.

Click to expand...

Thank you for sharing this!

Amamba said:

Depending on the lens, I can get OK results from Nex 6, but it doesn't really have DSLR like night focusing ability yet - I was able to acquire focus in near darkness with my Canon (but then, the high ISO wasn't that good). Also with PDAF you get faster focus but also back and front focusing issues... it's a trade-off.

Click to expand...

My A100 DSLR had trouble focusing in poor light. It would refuse to take photos, sometimes! That was annoying. I eventually figured out to change it to "release on shutter", and at least it will let me take the &#*^ photo. Anyway, the Nex-6 camera seems to have release-on-shutter already; if I'm impatient, I can just punch the button. I'm not sure that the Nex-5 does this. Either camera will take something within a second, but in poor light, sometimes it will not focus properly; I have much better results with the Nex-6. On Halloween, I was taking photos while walking very dark streets sometimes with flash, but also without, and it seemed to do OK considering. Then again, it may have found points of light that were high enough in contrast.

Amamba said:

As I said it's also very lens dependent. In really dim conditions (e.g. a glowstick birthday party with lights basically off) any lens will struggle. In "normal" dim conditions, e.g. a poorly lit karate dojo, I am getting good results with Sigma 30/2.8, but the faster Sony 50/1.8 suffers from slow and hunting AF. The biggest problem is using a long tele in poor light, as there's really just one E mount option.

Click to expand...

With the Nex-6, I used the kit lens at a karate event. It worked pretty well, actually -- surprised me, as I expected it to be pretty poor. Sure, my shutter speeds were a bit low, but I could always go for higher ISO. I tried to strike a balance, as there's always slow movement where things will look good. Fast movement was a bit of a blur with mixed results -- sometimes I like motion blur to indicate... motion.

I've used a 50/1.7 before in similar lighting and events, but I often have mixed results with manual focus. I know, it's the photographer's fault, but sometimes I just have enough to worry about.

Amamba said:

And to add, I am using manual focusing whenever I can anyway, it's the only way to achieve critical focus 100%, DSLR or not. I would use Live View on my T3i for critical portrait shots, and the Nex is so much better in this respect.

Click to expand...

The magnification is so good for manual focusing, I can't go back to an OVF!

PVCdroid said:

viking79 said:

One of the biggest complaints I notice too is that if you put the focus point on the face, if your subject is back lit the camera will often focus on the hair in line with the ears since the light is making it nice and high contrast. This makes the eyes a bit soft. This is mostly with the 50mm f/1.8. With the kit lens it probably won't be noticeable.

It sounds like a lot of work, but it isn't.

Eric

Click to expand...

Face detection works well in the situation you're describing above but you are stuck with multi-focus area setting. I do wish face detection worked on dogs/cats. Ha. Direct Manual Focus (DMF) works well for me and I double check and adjust the AF focus by turning the focus ring while shutter is halfway depressed.

Click to expand...

Thanks, forgot to mention DMF. I found face detection didn't work well, at least with non hybrid focus cameras. It finds the face fine, but focuses on highest contrast area in box, which is usually the background or hair.

Eric

try swtiching OFF the focus lamp in the menu .. and make sure you have updated your camera and lens to the latest firmware

even though it shounds crazy switching OFF the focus lamp made AF quicker for me

Thanks for all the replies.

The assist light I stopped using a long time ago (due to the annoying light beam) and it didn't help much anyway.

Yes, I love my 2005 Canon 5D with my prime lenses but sometimes I just don't bring that heavy thing with me and want something lighter.. and the 5D doesn't do video

IQ of the nex is really great no complains here. Besides the kit lens I own the sigma 30mm f/2.8 and use two c/y zeiss lenses I also use on my 5D from time to time.

On my 5D I'm used to focus on the eyes and get a AF comfirm even in dim conditions.

With the nex I need manual adjustment (focus on high contrast clothing for instance and then adjust) only this takes time. The screen can get too dim as well in those conditions so you can't clearly see if eyes are in focus or not.