Question on Relation between Manual Focus and Focus Area

[CatherineA]

The Sony manual explains that the Focus Mode is selected based on the movement of the subject. Manual focus is one of the options. Focus Area is a function to be used "when it is difficult to focus properly in auto focus mode." There is no section for manual and that led me to think that whatever the Focus Area was set to wouldn't have an impact on the photo.

I experimented by taking a series of photos in manual focus. The only feature that I changed in my settings was the Focus Area. The resulting photos differ in their brightness level and I don't understand why. I hadn't changed the metering mode and I used a remote to take the photos so there were no slight changes in movement. I did a few series and there were always differences in brightness.

I must be misunderstanding something. Could someone please tell me what that is?

[William W]

The operation of some cameras' TTL Light Meters, in some Metering Modes, may be linked to the Focus Point and or the "Focus Area" (Sony's Term).

I am ignorant of the nuances of the Sony Camera you have, in fact I don't know which one it is, that you have, nevertheless, the above could be a logical reason for the exposure differences that you attained.

WW

[CatherineA]

Thank you Bill, that sounds like the probable explanation.

I should have added that the camera that I took the photos with is the A7riii. It's mirrorless.

Also, the exposure is the same in all the photos but it is the "brightness value" in Lightroom that varies from photo to photo.

[dje]

Hi Catherine

Apparently the latest Sony cameras have a feature which allows you to link the Spot Metering point to the Focus point as explained in this video. Note that this is for spot metering only. My a6000 doesn't have this feature but your camera would have this.

However from your latest post, this is not what is happening as you say the exposure doesn't change. Not sure why the "brightness value" would change in LR, not even sure what that is!

Dave

[CatherineA]

Thanks Dave. That is really useful to know about the Spot Metering.

I need to look up what "brightness levels" in LR is all about. And in addition to that, it is strange whatever is going on when I change Focus Area because when I look at the four photos, they sure all look different exposures - from considerably too dark to too bright. I would post the photos and their LR library pages but perhaps it is too specific to my camera to be of general interest.

Maybe when the camera is in Manual Mode it ignores the metering setting I had dialled in and instead meters off of the Focus Area...

[pschlute]

i am confused how the exposure can be the same , but the "brightness value" is different ? Where in LR are you seeing this "brightness value" ?

I am assuming all 4 photos are identical scenes ?

[CatherineA]

Hi Peter,

The "Brightness Value" is directly above "Exposure Bias" in the Library Module in LR. Tomorrow I will post a pair of photos together with their info and histograms from the Library Module of LR. With today's photos I just randomly changed the Focus Area four times without making a note of which ones corresponded to which profiles - I was just surprised to see there was any change. Tomorrow I will note which Focus Areas do what.

Yes, all photos are of an identical scene.

[JBW]

The Sony manual explains that the Focus Mode is selected based on the movement of the subject. Manual focus is one of the options. Focus Area is a function to be used "when it is difficult to focus properly in auto focus mode." There is no section for manual and that led me to think that whatever the Focus Area was set to wouldn't have an impact on the photo.

I experimented by taking a series of photos in manual focus. The only feature that I changed in my settings was the Focus Area. The resulting photos differ in their brightness level and I don't understand why. I hadn't changed the metering mode and I used a remote to take the photos so there were no slight changes in movement. I did a few series and there were always differences in brightness.

I must be misunderstanding something. Could someone please tell me what that is?

My Sony Alpha a58 and 68 have the same set up. I'm no techie so if this explanation is factually wrong in some places hopefully the techies will correct me.

You have a choice in manual mode of how and where you want to put the focus. You can choose center, wide, zone or flexible. Each one composes your shot differently in relation to where they pull in information about brightness.

Here are some good links to help you.

[pschlute]

Hi Peter,

The "Brightness Value" is directly above "Exposure Bias" in the Library Module in LR.

Mmmmm, Cant see that in LR. I am using LR Classic cc.

But it sounds like you have your camera set up to take an exposure reading biased towards where you have a selective focus point. In that case I would expect four pictures with four different focus points to have four different exposures. But you say the exposure (ISO/Shutter/Aperture) is the same for all 4 shots ?

[CatherineA]

My Sony Alpha a58 and 68 have the same set up. I'm no techie so if this explanation is factually wrong in some places hopefully the techies will correct me.

You have a choice in manual mode of how and where you want to put the focus. You can choose center, wide, zone or flexible. Each one composes your shot differently in relation to where they pull in information about brightness.

Thank you Brian! I think that's what's happening. Really glad to understand this - it will make going forward in MF so much easier and with far fewer "what the heck" surprises.

And thanks for those helpful links too!

Here are some good links to help you.

[CatherineA]

Mmmmm, Cant see that in LR. I am using LR Classic cc.

But it sounds like you have your camera set up to take an exposure reading biased towards where you have a selective focus point. In that case I would expect four pictures with four different focus points to have four different exposures. But you say the exposure (ISO/Shutter/Aperture) is the same for all 4 shots ?

Hi Peter,
I think I see now where I messed up. I hadn't picked up on the significance of LR using the term "Exposure Bias" - I am still learning LR and didn't realize this wasn't the usual term used. I think that the situation is what Brian has suggested. I hadn't changed the focus from photo to photo, so the focus points are the same in all of them.

It is not how I expected metering to work. I thought that that would be solely determined by my choice of "Metering Mode." Good to know now that that is not the case. And thanks for tipping on to the fact that "Exposure Bias" was. indicating exactly that!

[Manfred M]

Catherine - "Exposure Bias" indicates that the user has used the Exposure Compensation controls to over-ride what the camera's metering system has determined to be the "correct" exposure. It is an information item that Lightroom pulls out of the image metadata and displays where you see it in the Library Module.

[CatherineA]

Catherine - "Exposure Bias" indicates that the user has used the Exposure Compensation controls to over-ride what the camera's metering system has determined to be the "correct" exposure. It is an information item that Lightroom pulls out of the image metadata and displays where you see it in the Library Module.

The exposure scale in my camera was at "0".

[JBW]

The exposure scale in my camera was at "0".

I have found that unless I set my ISO to auto my camera will not register the exposure compensation I apply. Perhaps your camera works the same way. Ie if I keep my ISO pegged at 100 (the base ISO) and dial in -3 exposure compensation I will see 0 exposure compensation in Capture 1 when I look at the shot information.

[pschlute]

Hi Peter,

Tomorrow I will post a pair of photos together with their info and histograms from the Library Module of LR.

Hi Catherine. Any chance of you posting these so we can get to the bottom of this?

[Stagecoach]

I need to look up what "brightness levels" in LR is all about.

This may help Catherine.

https://blog.thomasfitzgeraldphotogr...using-exposure

[CatherineA]

Hi Catherine. Any chance of you posting these so we can get to the bottom of this?

Focus Area: Wide



Focus Area: Zone


Focus Area: Centre


Focus Area: Flexible Spot Large


Focus Area: Expand Flexible Spot


They all have different histograms. The focus was on the face for each photo and the Metering Mode was the same for all photos (Multi).

[CatherineA]

This may help Catherine.

https://blog.thomasfitzgeraldphotogr...using-exposure

Thank you very much Grahame. That's a really useful link!

[Stagecoach]

They all have different histograms. The focus was on the face for each photo and the Metering Mode was the same for all photos (Multi).

There's a possibility the light caused this variation due to frequency.

Can you tell us what sort of light this is please?

[pschlute]

There's a possibility the light caused this variation due to frequency.

Only explanation that makes any sense, the exposure of all 5 images is 1/250; f1.8; ISO 400.