An unexpected result when using exposure spot metering on my camera.

[Panama Hat & Camera]

I hope this thread can be useful for anyone experiencing a similar situation, especially for Nikon photographers using D5200, D5300, D5500 and D5600 cameras.
Some time ago, I saw a small hawk over a palm leaf and decided to take a photo of it. The bird was a little far away, it was in the shade and the light condition was unfavourable, but I wanted to test my Nikon D5300 and register the presence of the bird. The settings of my camera were shutter priority, AF-S (single-servo autofocus), single point autofocus (in the center), exposure spot metering (because of the light condition) and auto ISO (*).
The result was this dark disappointing photo.

#1- The disappointing picture I took.


I didn't expect a great picture, but a photo with more light (like the following one).

#2- That was roughly what I expected.


Trying to understand what happened, I verifyed the settings of my camera using the softwares Capture NX-D and Irfan View.

#3- According to Capture NX-D software, the focus point position was the center of the photo.


#4- The Irfan View software confirmed that the exposure metering method used was "spot point" (I drew two diagonals to confirm the center of the photo).


Everything was ok (but not the photo)!
I had already read both manuals of my camera when I bought it (in 2014), but I did a search in the D5300 Reference Manual (the most complete) to find out what area was covered by the spot metering and I found the following explanation: "Spot metering: choose this mode to ensure that subject will be correctly exposed, even when background is much brighter or darker. Camera meters current focus point; use to meter off-center subjects". That was my case and this statement was exactly the reason of my choice of spot metering! But I didn't find any information about the area covered by the spot metering. This way, I continued without to know why my photo was so dark!
I asked Nikon (in Brazil), but I couldn't get a useful answer (I prefer to comment this subject in other thread).
Continuing my search for a proper explanation, I reread the other manual (the D5300 User's Manual). In the Specifications part I found this much more objective information: "Spot metering: Meters 3.5 mm circle (about 2.5% of frame) centered on selected focus point". That was the information I needed! (Later I discovered that the same information was available in the specification part of the D5300 Reference Manual).
The dimensions of the D5300 sensor are 23.5 x 15.6 mm, then 3.5 mm corresponds to 14.9% of the width and 22.4% of the height of the sensor. I drew (in the center of the original picture) a circle with a diameter of 22,4% of the height of the photo. This showed me that there was dark and light areas within the spot metering area, what probably misled the exposure metering system. That was the reason why my picture was so dark!

#5- The area covered by the spot measurement (a circle with a diameter of 22,4% of the height of the photo).


Extra infos:
A- This is about the center-weighted metering.
"Center-weighted metering: Weight of 75% given to 8 mm circle in center of the frame". This corresponds to 34,0% of the width and 51,3% of the height of the sensor. Only for comparison, I drew (in the center of the original picture) a circle with a diameter of 51,3% of the height of the photo.

#6- The areas covered by the spot metering and center-weighted metering (circles with diameters of 22,4% and 51,4% of photo height).


B- To help Nikon D5200/D5300/D5500/D5600 users, I plotted the positions of focus sensors and the areas covered by spot and center-weighted meterings.

#7- D5300 viewfinder (the positions of focus sensors and the areas covered by spot and center-weighted meterings).


(*) The information I used automatic ISO was written after seeing Peter's question.

Comments and opinions are welcome.
Cheers,
Antonio.

[xpatUSA]

Antonio,

Very good demonstration!

I spot-meter all of the time and, as you have shown, it does pay to know the spot circle diameter!

I remember doing the same research for a Nikon D50 when trying to measure the brightness of luminous watch hands.

Perhaps that area just below the bird would have given a better recommendation from the metering ...

... or that big leaf to the lower right.

[Manfred M]

Antonio - the problem is that our cameras meters are reflected light meters and will properly expose to a middle gray. If the area that is being metered is not middle gray, the image will be overexposed Or underexposed. Try metering a target that is pure black or pure white and your camera will end up exposing them so they look the same

I rarely spot meter outside of a studio situation where I am lighting the background to a specific level. The sample area tends to be too small and not representative of the scene.

I tend to look at the histogram when shooting in this type of lightning to ensure that I get a usable exposure.

[xpatUSA]

Antonio - the problem is that our cameras meters are reflected light meters and will properly expose to a middle gray. If the area that is being metered is not middle gray, the image will be overexposed Or underexposed. Try metering a target that is pure black or pure white and your camera will end up exposing them so they look the same

Manfred, it could be that the OP is well aware of how metering works, although a few of us might benefit from the above.

I rarely spot meter outside of a studio situation where I am lighting the background to a specific level. The sample area tends to be too small and not representative of the scene.

On the other hand, some others of us are quite happy to poke around in the scene before us and make our own minds up as to an appropriate exposure.

I tend to look at the histogram when shooting in this type of [lighting] to ensure that I get a usable exposure.

[Shadowman]

Whenever I'm shooting in similar conditions I get a warning, either "subject is too dark" on the LCD or I get the blinking "flash-bolt/?" on the right side of the camera's viewfinder. So if you ignore those warnings and still take the shot without trying to adjust the camera settings you'll get exactly what you get.

[pschlute]

Antonio what was the maximum aperture of the lens you were using, and did you use auto ISO ?

The reason I ask is that the exif shows the aperture used was 5.6 and also shows a "max aperture" field of 5.66

If the lens indeed does have a max aperture of 5.6 and you were using a fixed ISO of 200, then in shutter priority you have run out of options for the camera to give you any more light irrespective of the spot metering area issue ?

Just a thought

[Manfred M]

Manfred, it could be that the OP is well aware of how metering works, although a few of us might benefit from the above.



On the other hand, some others of us are quite happy to poke around in the scene before us and make our own minds up as to an appropriate exposure.

Reading what Antonio had written made me suspect that he was not entirely sure as to how a camera’s light metering system works. The image is back lit and his tends to cause most people some level of grief in nailing the exposure. There’s a lot of sky influencing this shot and when I look at how bright the sky appears in the first image, close to middle gray, it suggests this is what has happened. Camera manuals generally do a poor job explaining how their metering systems work. I find then explanation of spot metering and centre weighted metering modes somewhat deficient as both of these metering modes are more sensitive to selecting an area that is middle gray than some of the other metering modes due to the small sample area.

Understanding the strengths and weaknesses of any type of metering tool is important in mastering ones camera and getting a good exposure. Using a spot meter to explore a scene is certainly one way of understanding exposure and I have used my one degree spot meter precisely for that purpose as well. It’s an interesting exercise and one of many ways to understand what is happening in a scene. The most important thing is to get the experience to understand the tools that we use and what they are telling us and how to compensate when we see specific lighting situations.

[DanK]

I think the problem is what Antonio concluded: the bird was smaller than the spot metering area.

IMHO, if one is concerned about the exposure of a small area that is illuminated quite differently from the rest of the image, spot metering is the ideal tool--provided that the area is larger than the metering spot. It's not a problem if the area should be lighter or darker than neutral gray; just choose the setting appropriately. I do this frequently. Set the camera in manual mode, meter off the area in question, and adjust the exposure the meter indicates to adjust for however much you want the area to be lighter or darker than neutral gray.

This is also a useful approach if you want to meter the extremes--for example, if there is a small bright area that you want to make sure isn't blown out.

[Panama Hat & Camera]

Antonio,

Very good demonstration!

I spot-meter all of the time and, as you have shown, it does pay to know the spot circle diameter!

I remember doing the same research for a Nikon D50 when trying to measure the brightness of luminous watch hands.

Perhaps that area just below the bird would have given a better recommendation from the metering ...

... or that big leaf to the lower right.

Ted,
I am very pleased to hear that you liked my thread.
Yes, I agree with you (to know the spot metering circle diameter is very important).
Thanks for commenting.
Antonio

[Panama Hat & Camera]

Manfred,
Thanks for commenting.

Antonio - the problem is that our cameras meters are reflected light meters and will properly expose to a middle gray. If the area that is being metered is not middle gray, the image will be overexposed Or underexposed. Try metering a target that is pure black or pure white and your camera will end up exposing them so they look the same

I know that camera meters compare scene reflected light with the luminance of light which is reflected from an object appearing as middle gray.

I rarely spot meter outside of a studio situation where I am lighting the background to a specific level. The sample area tends to be too small and not representative of the scene.

In the case of my picture, the sample area was too large for a correct exposure.

I tend to look at the histogram when shooting in this type of lightning to ensure that I get a usable exposure.

I take photos of birds and other animals that are very sly and flee if they feel threatened, so I can't always see the histogram and correct the exposure. It is easier to do the corrections when I'm using my superzoom camera (a Canon SX50 HS) because I can see the histogram before taking the picture.

[Panama Hat & Camera]

Whenever I'm shooting in similar conditions I get a warning, either "subject is too dark" on the LCD or I get the blinking "flash-bolt/?" on the right side of the camera's viewfinder. So if you ignore those warnings and still take the shot without trying to adjust the camera settings you'll get exactly what you get.

John,
Thanks for commenting.
The photo is not underexposed (the ISO was automatic), so there was no warning like "the subject is too dark".
Antonio

[Panama Hat & Camera]

Peter,
Thank you for your comments.

Antonio what was the maximum aperture of the lens you were using, and did you use auto ISO ?

I was using a Nikkor 55-300mm f/4.5 - f/5.6 lens at 300mm. The maximum aperture was f/5.6 and I was using auto ISO (this information was missing from my thread).

The reason I ask is that the exif shows the aperture used was 5.6 and also shows a "max aperture" field of 5.66

If the lens indeed does have a max aperture of 5.6 and you were using a fixed ISO of 200, then in shutter priority you have run out of options for the camera to give you any more light irrespective of the spot metering area issue ?

Just a thought

I chose shutter priority because I knew the aperture would be maximum (otherwise if I used aperture priority, the exposure time would be only 1/320 and ISO would be 100).
Antonio

[Panama Hat & Camera]

Reading what Antonio had written made me suspect that he was not entirely sure as to how a camera’s light metering system works. The image is back lit and his tends to cause most people some level of grief in nailing the exposure. There’s a lot of sky influencing this shot and when I look at how bright the sky appears in the first image, close to middle gray, it suggests this is what has happened. Camera manuals generally do a poor job explaining how their metering systems work. I find then explanation of spot metering and centre weighted metering modes somewhat deficient as both of these metering modes are more sensitive to selecting an area that is middle gray than some of the other metering modes due to the small sample area.

Understanding the strengths and weaknesses of any type of metering tool is important in mastering ones camera and getting a good exposure. Using a spot meter to explore a scene is certainly one way of understanding exposure and I have used my one degree spot meter precisely for that purpose as well. It’s an interesting exercise and one of many ways to understand what is happening in a scene. The most important thing is to get the experience to understand the tools that we use and what they are telling us and how to compensate when we see specific lighting situations.

My good friend Manfred, once again you are underestimating me!
I don't know about electronics or algorithms, but in general, I know how a camera's light metering system works (I've read CiC tutorials, internet articles, and I have some books on digital photography).
I know I'm just a retired engineer and an enthusiastic photographer (not a professional or an artist) and a person who likes the nature (that's why I take pictures of birds, squirrels and other free animals), but a photographer who have many things to learn (including English).
As I wrote before, I can't always see the histogram and correct the exposure. In the case of this photo, the hawk flew away when I was seeing the photo on the back screen of my camera. There was nothing else I could do, but the picture was taken in RAW and I was confident that I could identify the bird (it's a yellow-headed caracara). https://en.wikipedia.org/wiki/Yellow-headed_caracara
I took this picture in December 2017 (three years after buying the D5300) and found out why it was so dark when I saw it on a computer (what I didn't know was the area covered by spot metering).
This thread is just a modest contribution for helping other photographers that experience a similar situation, especially for Nikon photographers using D5200, D5300, D5500 and D5600 cameras (I believe that the Cambridge in Colour is "A LEARNING COMMUNITY FOR PHOTOGRAPHERS").
For these photographers, the synthesis of this thread is the image #7.
Thank you for commenting.
Best regards,
Antonio.

[Panama Hat & Camera]

I think the problem is what Antonio concluded: the bird was smaller than the spot metering area.

IMHO, if one is concerned about the exposure of a small area that is illuminated quite differently from the rest of the image, spot metering is the ideal tool--provided that the area is larger than the metering spot. It's not a problem if the area should be lighter or darker than neutral gray; just choose the setting appropriately. I do this frequently. Set the camera in manual mode, meter off the area in question, and adjust the exposure the meter indicates to adjust for however much you want the area to be lighter or darker than neutral gray.

This is also a useful approach if you want to meter the extremes--for example, if there is a small bright area that you want to make sure isn't blown out.

Dan,
You are the only one who fully understood my thread! Everything you said is correct. Congratulations!
I found out why the image was so dark when I saw it on a computer (what I didn't know was the area covered by the spot metering).
Thank you very much for commenting.
Cheers.
Antonio

[Panama Hat & Camera]

Manfred, it could be that the OP is well aware of how metering works, although a few of us might benefit from the above.



On the other hand, some others of us are quite happy to poke around in the scene before us and make our own minds up as to an appropriate exposure.

Ted,
I was not fair to you!
You also fully understood my thread!
Cheers,
Antonio.

[Stagecoach]

Good investigative work and example Antonio.

It's always useful and an aid to many who are learning to see examples of where things have not worked out and why.

[MrB]

Thank you Antonio for your interesting and enlightening posts. I had no idea that the spot metered was so large - I had assumed it was a pimple, not a carbuncle!

Philip

[Panama Hat & Camera]

Good investigative work and example Antonio.

It's always useful and an aid to many who are learning to see examples of where things have not worked out and why.

Grahame,
Thank you for your kind words. My intention is to help someone who comes across a similar situation.
Thanks for your comment.
Antonio.

[Panama Hat & Camera]

Thank you Antonio for your interesting and enlightening posts. I had no idea that the spot metered was so large - I had assumed it was a pimple, not a carbuncle!

Philip

Philip,
I also thought the area covered by spot metering was tiny.
Thank you for commenting.
Antonio.

[Panama Hat & Camera]

It's really a great and helpful piece of info. I'm glad that you just shared this useful information with us. Thank you for sharing this good information.

Lilly Ann,
I'm glad you think my thread is helpful. My intention is to help anyone experiencing a similar situation
Thanks for your comments.
All the best!
Antonio.