P30 pro: Flash below 1/15 shutter not working correctly?

[Android Central Question]

I got the p30 pro and I noticed on pro mode that when I shoot slower than 1/15 shutter speed, the flash burst but the picture remain dark as if the photo was taken too late from the flash.

Issue?

 

[B. Diddy]

I moved this to the P30 Pro forum for more specific traffic.

 

[Mooncatt]

Depending on how dark it is and the subject, it could be that the flash isn't strong enough (phone LED flashes are notoriously weak). You may want to try increasing the ISO setting, but that risks adding noise. Longer shutter times could work, but at the risk of adding motion blur. Otherwise, find a way to add more ambient light.

 

[Rukbat]

The LED "flash" on a cellphone is good for about 5-10 feet (depending on the phone) - after that it has no effect on lighting. So, as Mooncatt said, you want to add more light, or get a remote flash that's triggered by the flash on the phone (photo supply stores sell them).

To prove it, go into a really dark room and take a picture at lower than 1/15 speed - of something a few feet away - even the wall. If there's something wrong, even if the wall is 2 feet from the camera it will appear dark. (It's possible that the synchronization isn't working at slow speed, it's just not usual.)

 

[Mooncatt]

...or get a remote flash that's triggered by the flash on the phone (photo supply stores sell them).

I doubt this will work. I have an off camera flash that can be triggered by the camera flash, but it does not respond to my phone's LED flash. I think it's they are too dim and not an instant hit like a true xenon camera flash.

 

[Fred98TJ]

Depending on how dark it is and the subject, it could be that the flash isn't strong enough (phone LED flashes are notoriously weak). You may want to try increasing the ISO setting, but that risks adding noise. Longer shutter times could work, but at the risk of adding motion blur. Otherwise, find a way to add more ambient light.

Increasing the ISO does not add more noise than what is already present.
In digital photography, ISO has nothing to do with exposure.

 

[Fred98TJ]

The LED "flash" on a cellphone is good for about 5-10 feet (depending on the phone) - after that it has no effect on lighting. So, as Mooncatt said, you want to add more light, or get a remote flash that's triggered by the flash on the phone (photo supply stores sell them).

To prove it, go into a really dark room and take a picture at lower than 1/15 speed - of something a few feet away - even the wall. If there's something wrong, even if the wall is 2 feet from the camera it will appear dark. (It's possible that the synchronization isn't working at slow speed, it's just not usual.)

You can’t use a flash (a real flash, xenon flash) with any modern cellphone cameras. You can probably get a remote flash to fire by triggering off the led flash on the phone, however all modern cellphone cameras have electronic shutters and you can’t use a standard, real flash with an electronic shutter.

 

[Jon Mar1]

Has anyone actually tried on an actual p30pro? I think there's a lot of confusion here and it not related to the distance nor the gear but with the actual phone. I shot a picture on pro mode on something real close and dark and the picture didn't register any flash at all. Just raising the flash at 1/15th has made the flash quite apparent in the picture, to even blown the exposure quite a lot. I actually had to put the led flash on Always On mode as a workaround below 1/15 to see a flash in the picture. It not even an issue with other phones (tried with my old Galaxy S7)

The LED "flash" on a cellphone is good for about 5-10 feet (depending on the phone) - after that it has no effect on lighting. So, as Mooncatt said, you want to add more light, or get a remote flash that's triggered by the flash on the phone (photo supply stores sell them).

To prove it, go into a really dark room and take a picture at lower than 1/15 speed - of something a few feet away - even the wall. If there's something wrong, even if the wall is 2 feet from the camera it will appear dark. (It's possible that the synchronization isn't working at slow speed, it's just not usual.)

 

[Mooncatt]

Increasing the ISO does not add more noise than what is already present.
In digital photography, ISO has nothing to do with exposure.

ISO is one side of the exposure triangle and does impact noise. Even if you have an ISO invariant sensor, increasing it still makes noise more apparent. It's especially problematic on phones due to the much higher pixel density compared to full sized cameras. A full frame may get you a decent image at ISO 6,400, but a phone is lucky to do well at ISO 400.

You can’t use a flash (a real flash, xenon flash) with any modern cellphone cameras. You can probably get a remote flash to fire by triggering off the led flash on the phone, however all modern cellphone cameras have electronic shutters and you can’t use a standard, real flash with an electronic shutter.

Wanna bet?


Shoot with my LG V20 and used an off camera flash triggered manually (I already mentioned the LED flash won't trigger a slave flash sensor). Mirrorless cameras are competing with DSLR's now. They are electric shutters and have no issues with xenon flashes.

 

[Mooncatt]

Has anyone actually tried on an actual p30pro? I think there's a lot of confusion here and it not related to the distance nor the gear but with the actual phone. I shot a picture on pro mode on something real close and dark and the picture didn't register any flash at all. Just raising the flash at 1/15th has made the flash quite apparent in the picture, to even blown the exposure quite a lot. I actually had to put the led flash on Always On mode as a workaround below 1/15 to see a flash in the picture. It not even an issue with other phones (tried with my old Galaxy S7)

I'm a little confused on the timing aspect. When you originally said shooting slower than 1/15" causes the problem, you mean 1/8", 1/3", 1/2", 3/4" and longer? The above and below references in this post threw me a bit.

Could you take a few of sample photos, one at 1/15", one faster, and one slower, all with the flash on? Welcome to the forums, and now you can upload those samples here. Also let us know the ISO of each (in case it was different). Your gallery app should have a menu option to view the image details, which would have that info in it. That will help us all get on the same page.

 

[Fred98TJ]

ISO is one side of the exposure triangle and does impact noise. Even if you have an ISO invariant sensor, increasing it still makes noise more apparent. It's especially problematic on phones due to the much higher pixel density compared to full sized cameras. A full frame may get you a decent image at ISO 6,400, but a phone is lucky to do well at ISO 400.



Wanna bet?
View attachment 302285

Shoot with my LG V20 and used an off camera flash triggered manually (I already mentioned the LED flash won't trigger a slave flash sensor). Mirrorless cameras are competing with DSLR's now. They are electric shutters and have no issues with xenon flashes.

In digital photography, ISO has nothing to do with exposure. Changing the ISO does not change the exposure.
The exposure triangle (in digital photography) is aperture, shutter speed and SnR (and/or adc circuitry).
If you take a pic and it’s “underexposed” (too dark for you) then raising the ISO (keeping the same aperture and shutter speed) will produce a photo with more visible noise because the exposure is still underexposed and has simply been “brightened” (exactly the same as turning the brightness up on your screen) so now your simply seeing the noise more (especially in the shadows) that was the results of the photo being underexposed to start with.
ISO is applied gain and the gain is applied AFTER the exposure has been made.
ISO is baked into the sensor at the time of production. It can not be changed (with a minor exception of a few sensor types).
If you take a photo at the base ISO (usually around 25 to 50 on cell phones) of say a solid color wall and the pic is “underexposed”, the pixels only “half full” (half saturated) of photons (light particles)and then raise the ISO and take the photo again with the same aperture, shutter speed and lighting conditions, the sensitivity of the sensor is not increased, the pixels will still only be half full (sensor half saturated) and the photo will still be “underexposed”. The increased ISO will simply cause more gain to be applied to the signal, AFTER THE EXPOSURE HAS BEEN MADE. As such, all the existing noise will be amplified also “brightened” and will be more visible in the photo.
The noise “problem” on cell phones is not due to pixel density, it’s due to the tiny pixel pitch which means crappy SnR. The tiny pixel pitch is also the cause of the, relatively, small DR of these small phone sensors.


Regarding the off camera flash. Take a picture and post it without all the light painting going on of a darkened area with a typical shutter speed.

Electronic shutters can only use HSS flash (real xenon flash). Those fire very, very rapid burst of light so that there is flash exposure as each row(s) of pixels in read off the sensor.
Not all cameras support HSS flashing photography and I don’t know of any cell phones that do.
The sensors in cell phone cameras are not global sensors. The typical sensor (non global) read the data off the sensor rows at a time and the sensor read time (not shutter speed) is much slower than the typical flash from a xenon flash unit (type flash duration of around 1/5 of a millisecond).
This is why, without using HSS an electronic shutter cam can’t use a real flash. The light from the flash would be finished before the whole sensor is exposed.
This problem (reading the data off the sensor row(s) at a time, is what causes the rolling shutter effect that’s often seen with electronic shutters.
Some cameras, mirrorless, wont even fire a flash when in electronic shutter mode, requiring the use to change to mechanical shutter mode.

 

[Mooncatt]

In digital photography, ISO has nothing to do with exposure. Changing the ISO does not change the exposure.

Being ISO invariant is a relatively new concept in digital photography, and only talked about as it relates to full sized cameras. I would be very surprised if any of that technology has filtered into smartphones yet, and didn't find any discussions on that.

https://digital-photography-school.com/iso-invariance-exposure-triangle/

https://photographylife.com/iso-invariance-explained

(They are somewhat long reads, but go into great detail about why selecting the right ISO still matters.)

The noise “problem” on cell phones is not due to pixel density, it’s due to the tiny pixel pitch which means crappy SnR. The tiny pixel pitch is also the cause of the, relatively, small DR of these small phone sensors.

Pixel pitch and density are directly related and are effectively synonymous terms for this discussion, to which we are in agreement.

Regarding the off camera flash. Take a picture and post it without all the light painting going on of a darkened area with a typical shutter speed.

Electronic shutters can only use HSS flash (real xenon flash).

That isn't what you said originally, and I was simply proving a point that your advice isn't true across the board. Of course in most situations you won't be able to use a stand alone flash, but that is due to timing requirements, not flash design. Some smartphones have had xenon flashes, and at least one Bluetooth controlled OCF with a xenon bulb has been developed for smartphones. The one in my above sample was a cheap one from Amazon, with no HSS ability. Rolling electronic shutters have little to do with stills. You can get the same effect with a film camera, given fast enough action.

https://photographylife.com/iso-invariance-explained

The takeaway here is knowing the limits of your equipment and working within them. I just happen to like pushing those limits.

 

[Fred98TJ]

Being ISO invariant is a relatively new concept in digital photography, and only talked about as it relates to full sized cameras. I would be very surprised if any of that technology has filtered into smartphones yet, and didn't find any discussions on that.

https://digital-photography-school.com/iso-invariance-exposure-triangle/

https://photographylife.com/iso-invariance-explained

(They are somewhat long reads, but go into great detail about why selecting the right ISO still matters.)



Pixel pitch and density are directly related and are effectively synonymous terms for this discussion, to which we are in agreement.



That isn't what you said originally, and I was simply proving a point that your advice isn't true across the board. Of course in most situations you won't be able to use a stand alone flash, but that is due to timing requirements, not flash design. Some smartphones have had xenon flashes, and at least one Bluetooth controlled OCF with a xenon bulb has been developed for smartphones. The one in my above sample was a cheap one from Amazon, with no HSS ability. Rolling electronic shutters have little to do with stills. You can get the same effect with a film camera, given fast enough action.

https://photographylife.com/iso-invariance-explained

The takeaway here is knowing the limits of your equipment and working within them. I just happen to like pushing those limits.

I’m not talking about ISO invariance (in regards to my statements about ISO) that’s something different. Btw, a ISO invariant sensor is simply one that has low read noise, particularly back end read noise. Two of my cameras are ISO invariant.
Regarding ISO (in digital photography), it’s simply not part of the exposure. Taking a photo and then raising the ISO and taking the photo again (assuming the same aperture, shutter speed, subject and lighting) does not change the exposure at the sensor. The totally raw data (exposure wise) is the same. What raising the ISO does is increases the gain (think of turning the volume up on your radio or tv as an example) of the signal data going from the sensor into the converters. This increase in signal gain is applied to the raw sensor data after the exposure has been made.

It’s easily observed using sw such as rawdigger or even a raw converter that allows you to view the raw data from the raw files without applying any of the instructions, from the exif data, to the image.
SnR is part of the exposure triangle.
The sensitivity of the sensor (base ISO as it’s often called) is baked in at the time of production and (with a very few exceptions) can not be changed.
If talking about a specific sensor size, then yes, increase in pixel density would mean a decrease in pixel pitch, however taking the blanket statement “increased density” is misleading and statements like this can lead to much confusion when overstated again and again by others. IMO, it’s better to state actual reason, decrease in pixel pitch. That way no one gets confused.
Now I’m assuming you know how electronic shutters work, however for those that don’t, here’s what happens. (This is simplified but accurate and I’m talking about rolling shutters here, not global shutters as no cell phone cameras use those). When you take a photo at a given shutter speed, let’s say 1/60 sec, the whole sensor does not make that exposure at the same time. The exposed pixels are read off the sensor one row at a time. What happens, simplified but accurate, is that the sensor is “turned off” the the the first row of pixels on the sensor is turned on for 1/60 of a sec (the shutter speed), then that exposure is locked and that row of pixels is read off the sensor. Depending on the sensor it’s fast but still takes time, typically maybe 8 microseconds. Now the sensor is turned off then the next row of pixels is turned on for 1/60 of a second (shutter speed) then offed and that row is read off the sensor, and on until all of the pixel rows have been exposed and read off the sensor. If the sensor, as example, has 2500 rows of pixels, then it takes 1/50 of a second (and this has nothing to de with the exposure time of 1/60 sec for each row of pixels) just to read all the rows and remember the rows are exposed one row at a time. If the whole sensor were continually exposed during the reading of the rows, then the last row would be exposed more than the first row. That’s why the sensor is basically turned off and on (again a simplified but accurate description).
The typical flash unit (real photographic xenon flash) has a total light duration (depending on its power) is from around 1/10,000 sec to around 1/30,000 or more. Now it should be pretty obvious the problem of trying to use a “real” flash with an electronic shutter. Then bottom part of the sensor would not get any exposure from the flash because the flash duration is too short.
Rolling shutter effects occur with stills as well as with video (which is simple a string of images). In our case above if there is fast action like a car driving past fast, then the position of the car when the top row of pixels is exposed (for the 1/60 sec) and when the bottom row of pixels is exposed wii have changed, thus the observed distortion. I’ll attach a screen shot of a photo (not a video) showing clear rolling shutter distortion.
You said some cell phones have xenon flashes and that is true. The Lumia N8, 808, and 1020 are three that do, however you should note that they have mechanical shutters.

Please always push the limits and try things and experiment. That’s the scientist in some of us, but let’s try to use objective truths or useful information when we talk in somewhat general terms, such as a “real” photographic flash (xenon) can’t be used with an electronic shutter (generally).
Cheers and everyone just go make photos.

 

[Jon Mar1]

I'm a little confused on the timing aspect. When you originally said shooting slower than 1/15" causes the problem, you mean 1/8", 1/3", 1/2", 3/4" and longer? The above and below references in this post threw me a bit.

Could you take a few of sample photos, one at 1/15", one faster, and one slower, all with the flash on? Welcome to the forums, and now you can upload those samples here. Also let us know the ISO of each (in case it was different). Your gallery app should have a menu option to view the image details, which would have that info in it. That will help us all get on the same page.

Here's pics of my pants sorry if it bad taste but i m in a dark spot and here you can clearly see the differences between 1/10th and 1/15. Took screenshots of the infos for proof

 

[Jon Mar1]

Here's more

 

[Mooncatt]

Wow, that is extremely odd. The only thing I can think of is like you suspected, the flash firing before the sensor is activated. Since no one else with this phone has commented, I'll go to the photos thread and comment to see if some of those users can test this on their phones and report here. That will help us determine if it's a problem specific to your phone or not. Alternatively, I'd start playing around with third party camera apps and see if they give the same result.

 

[Jon Mar1]

I went to a phone store and was able to reproduce the issue on phones that are demonstrators. It hard to explain the issue to tech savvy people because they are completely in disbelief until I show them in front of their eyes. I've been working around the problem by letting the led flash always on. I guess it a very specific bug to people who use the feature like me under specific occasion ie doing drag shutter type of photography which require low light

 

[Mooncatt]

I went to a phone store and was able to reproduce the issue on phones that are demonstrators. It hard to explain the issue to tech savvy people because they are completely in disbelief until I show them in front of their eyes

With that being the case, this is something Huawei will have to fix. I'd try reaching out to them and see if they have a fix for it.