Who wants a smarter P mode?

Msmoto

One of our most knowledgeable members has suggested the "P" mode uses a 30,000 image data base to make the decisions...It sounds like this works for TTJ

Correlli

One of our most knowledgeable members has suggested the "P" mode uses a 30,000 image data base to make the decisions...It sounds like this works for TTJ

I think this is a misunderstanding. The matrix metering uses an image database of 30,000 images to find the correct exposure for a given scene. This metering results in an exposure value (EV) that is then used with the graph shown by Ade to select the "correct" combination of f-stop and exposure time. But the same "intelligent" EV is used if you are in A or S mode.

SquamishPhoto

It might be coincidence that TTJs shots got the right DOF or a hidden function - as I said, I want to try it.

We'd need to know the lens he used and the subject distance. Other wise its kind of pointless because with certain focal lengths at certain distances it can become next to impossible to gain enough depth of field through aperture adjustment and with others it the converse can be true - that, at the right distance with the right focal length, one needn't adjust the aperture much at all in order to gain enough DOF to render all subjects in focus . Lets see a photo with the exif data and then we'll understand more.

dissent

OK, we in the amateur's gallery have run out of popcorn. Can you folks hold on for a couple of minutes . . .


. . . OK, we're back. Please continue. Have at it.

Ade

Continuing on then...

To better understand the exposure process we can break down the three steps our Nikons take in when we press that shutter button:

1. Autofocus

The camera's first task is to determine the focus distance.

There have been a ton of AF improvements throughout the years, including technologies such as face detection and the ability to select numerous customizations.

But the basic focusing process is still the same: a focus point will be selected, then the focus distance will be determined either using phase-detect or contrast-detect.

The relevant settings during the process are the Focus Modes (AFS, AFC) and the AF Area Modes (e.g., single point, multi-point, 3D, auto-area). Data from the exposure meter is used to assist with certain functions (e.g., to determine skin tones for face detection).

The primary output of this step is the focus distance. P-mode does not affect this step at all.

2. Metering

The next step is to determine the lighting conditions. This is where the Metering Modes come in (Spot, Center Weighed, Matrix).

The Matrix metering mode is so sophisticated these days. It combines a myriad of sensor data (including the focus distance determined in Step 1) and camera settings with the 30,000 image pattern database mentioned by Msmoto.

With any of the metering modes, the camera calculates an appropriate Exposure Value (EV) number. Again, P-mode does not affect this step at all.

3. Exposure Setting

The camera now must translate the calculated EV number into an actual exposure setting (aperture, shutter and ISO). It does so according to the current Exposure Mode (P, A, S, M) plus a few other factors (e.g., Auto ISO setting, flash mode, exposure compensation, etc.)

It is only now that P-mode comes to play. As explained earlier, P-mode takes the EV number (calculated in Step 2) and simply translates it into the exposure setting using the programmed chart/table mentioned earlier in the thread. E.g., if the meter came up with EV 6, P-mode follows the chart and sets the camera to 1/15th and f/2.

Nowhere in the P-mode process will the camera look for a group of people, try to determine the required DoF to capture all of them in focus, then set the aperture appropriately to achieve that DoF.

The focus determination happened all the way back in Step 1 -- long before P-mode became relevant -- and resulted in the focus distance information (not a range of focuses or a required DoF).

Note: older consumer Canon DSLRs (e.g., the Rebel T3i) had a special A-DEP mode which tried to do what TTJ suggests: determine the DoF range from the nearest and furthest auto-focus points, then set the aperture (and shutter) automatically.

The A-DEP mode was designed with group shots in mind, but it didn't work very well, and Canon removed this functionality from their newer DSLRs.

rmp

This is bad. You people have made me go back and read the manual.

According to Thom Hogan's D800 manual, page 261, the face detection logic affects both the focusing and the metering. Therefore, if multiple people are in a picture, the EV value must account for multiple people. And if they are at different distances from the camera, DoF should be considered somewhere in the logic. (Don't ask me where.)

Yes, I still want a smarter P-mode. I can visualize one dial controlling F-stop, one controlling shutter speed, and one controlling ISO. Then P-mode sets them all-- but I can override any one and P-mode sets the other two. If I override any two, P-Mode sets the last one. If I override all three, P-Mode just laughs and lets me do it anyway.

Ade

Yes rmp, if you read my post above, you can see in Step 1 (autofocus) I already mentioned that "Data from the exposure meter is used to assist with certain functions (e.g., to determine skin tones for face detection)."

But it is wrong to conclude that the EV value accounts for multiple people at different distances (it doesn't). It is also incorrect to say that DoF is considered for setting aperture (it is not).

In any case, none of the above has anything to do with P-mode, which doesn't take affect until Step 3 in my post.

You may want to read Thom Hogan's description of P-mode starting at page 298 (in version 1.05 of his eBook).

bland

You may want to read Thom Hogan's description of P-mode starting at page 298 (in version 1.05 of his eBook).

What Nikon Camera was Thom Hogan using?

Ade

Hi bland, I was referring to Thom Hogan's "Complete Guide to the Nikon D800 and D800E" mentioned by rmp.

bland

@Ade ... Thanks for the info. I need to pick a copy of that up.

heartyfisher

actually the Pmode "exposure setting" takes into account the focal length to set the shutter speed, the actual graph selected depends on focal length ..

TaoTeJared

@TaoTeJared: Page 94 of the manual states:

"Auto-area AF: The camera automatically detects the subject and selects the focus point; if a face is detected, the camera will give priority to the portrait subject. The active focus points are highlighted briefly after the camera focuses; in AF-C mode, the main focus point remains highlighted after the other focus points have turned off."

They don't use the term "face recognition", but it's working in normal view as well. LiveView just has an additonal Portrait AF mode. Now, if I'd focus a person who's just in hyperfocal distance and using a wideangle lens/zoom which doesn't have f/1.4 but maybe f/2.8 or less open aperture it might happen that the camera choses accidentally a suiting aperture.

To calculate DOF, the cam would have to focus to each subject separately and continuously. I never saw that happen but the impact of a DOF automatic would be huge: Focus-stacks out of the cam, pointing to closest and farest points and getting a suiting aperture back - wow.

Just because some have seemed not to go back and read the last few comments, JJ_SO found it in the manual.
I guess I should read it more often!

JJ_SO

Me too. I was not to sure about. On the other hand, "P" is something new to me to discover, as well as the advanced AF settings.

John

actually the Pmode "exposure setting" takes into account the focal length to set the shutter speed, the actual graph selected depends on focal length ..

As far as I know you are incorrect.
The graph that Ade showed was all that the camera uses to pick the aperture / shutter speed combination based on focal length.
You can do the test yourself.
Take a zoom tele lens (70-200, 70-300, 80-400,...)/
Aim the camera at an evenly lit white or gray wall while zoomed out. Look at the shutter speed.
Now zoom in as much as you can.
According to your statement the shutter speed should increase. This is not the case.
The description Ade gave is exactly what I see on the D800 myself and corresponds to everything I found in related literature (D800 manual, Thom Hogan's guide,...)

There is a feature called auto iso. This feature allows the camera to automatically increase the iso (in a configurable range; e.g between iso 100 and iso 1600) if the shutter speed falls below a certain level. This shutter speed can be a value that you set (e.g. 1/500 s) or it can be determined by the camera based on the focal length of the lens.

rmp

Ouch! Again I am forced to read a manual. This is awful!

Thom Hogan's D4 manual page 35 states that in live-view AF-Area mode if 35 faces are recognized, and the focus point is the nearest face. The multi-selector can be used to change it. I like that focus point and the additional control. But with 35 faces, there is a good probability that they will need different exposures to bring out detail. So, how does face-detection, skin-tone exposure set f-stop selection? And does it still work in A-mode?

dormant

Some film Nikons had two P modes, P and PH. For the life of me, I can't remember what the PH mode was for.

It can't have been very useful.

John

Ouch! Again I am forced to read a manual. This is awful!

Thom Hogan's D4 manual page 35 states that in live-view AF-Area mode if 35 faces are recognized, and the focus point is the nearest face. The multi-selector can be used to change it. I like that focus point and the additional control. But with 35 faces, there is a good probability that they will need different exposures to bring out detail. So, how does face-detection, skin-tone exposure set f-stop selection? And does it still work in A-mode?

It's actually very simple.
Live view auto focus area mode will try to focus on a face if it detects one.
If it detects multiple faces it will focus on the closest face.
So, this would be just as if you focussed on the closest face using manual focus. Nothing magical happening here.

Next, the camera will try to determine the correct exposure.
Normally this is done by selecting an exposure (= amount of light hitting the sensor) that will make most of the image middle gray.
However, if the light meter detects skin tones then the light meter will try to select an exposure that correctly exposes the faces. For example if the subject is standing in the shade then the light meter will overexpose the sunshine areas in order to have visible, correctly exposed faces. (All this within certain limits based on a reference set of 30000 images)
Nikon light meters can do this because they see colors as opposed to Canon light meter)
Now the required exposure (total amount of required light) is known to the camera.

If you are in A mode the shutter speed will be selected based on the chosen aperture in order to get the required exposure.
If you are in P mode the exposure will be used to look up both aperture and shutter speed for that exposure (see the graph shown by Ade). Focal lenght, subject, focal distance,... is not taken into account.

John

Some film Nikons had two P modes, P and PH. For the life of me, I can't remember what the PH mode was for.

It can't have been very useful.

PH mode was a program mode with a different aperture/shutter speed/exposure value graph.
For a give exposure value it had a higher shutter speed and correspondingly more open aperture compared to the normal P mode. PH was intended for sports photography and or long tele lenses.

heartyfisher

Thought I should give this a bump as we are talking about P mode again :-) which I use primarily on my Nikon cameras..

PS : Looks like I had left this thread hanging with an issue unresolved ... regarding the Focal length setting changing the speed selected in P mode.

nukuEX2

What is "P" mode? )

As Ken Rockwell has stated "P" is for the "Professional"... )

sevencrossing

As Ken Rockwell has stated "P" is for the "Professional"... )

Don't laugh. I have a friend, who is a successful professional photographer, and genuinely believes this to be true

heartyfisher

As I have stated several times my camera is in P mode most of the time...
There seems to be a perception that the P mode user surrenders the image setting to the camera. Far from it.
I find that I can get to what I want faster and safer with P mode and the dials and the +/-.

WestEndFoto

You will have to program this programmable p mode depending on your shooting style. May as well just use a, s or m mode.

rmp

The way I use "P" mode it should be renamed to "Speed Mode" -- when I do not have time to select any settings at all, I am very grateful that my camera was in "P" mode. For serious stuff, more and more often I find I am using M mode with auto ISO. A while back, I used A mode most of the time.

I hope Nikon continues to improve the artificial intelligence in P mode. My grab-and-shoot shots need it.

sevencrossing

I hope Nikon continues to improve the artificial intelligence in P mode. My grab-and-shoot shots need it.

With the Lily Drone you not even need to point the camera in the right direction