[stevebrot]

I use M-mode; in fact, I use M-mode a lot. I am also fond of my K-3's built-in bracket function and use it frequently. I guess that makes me proficient with both except that I had not used the two together until yesterday when exercising the combination as part of a troubleshooting request. After several hours figuring out how it works, I am perplexed.

Is my camera broken?!
The first thing I noticed that has nothing to do with M-mode is that "one-push" bracketing seems to be active regardless of whether the feature is enabled in the custom setting menu. I did not notice this before yesterday and the behavior persists even after updating from firmware v1.10 to v1.30. Is it supposed to do that? Edit: I figured it out...

Down the rabbit hole...
Normally, I would not have considered using the "Exposure Bracketing" drive mode in conjunction with M-mode. After all, it is manual mode and manual mode is all about full control of exposure. Doing a bracketed exposure series manually is very straightforward and easy. Doing the same using the bracketing feature generally works pretty well too, despite a few quirks that bear being attentive to. I will be posting those findings separately in another thread. This thread is about anomaly, as in Star Trek.

Star Trek anomalies fall broadly into several categories: energy, spacial, temporal, and so on. Thankfully, I don't believe I ran into any of those. What I encountered instead was a vexing "aperture anomaly" where the e-dial behaves according to several unconventional notions of what constitutes 1/3 stop. In short, I found two fairly serious bugs. To be clear on how to reproduce, here is the setup:

Setup

• K-3, firmware v1.10 or higher
• FA 35/2 mounted
• EV steps: 1/3 stop (default)
• Bracketing Order: "- 0 +"
• D-Range Settings: all off
• Manual ISO
• Program Line: Normal
• Green Button Action: Program Line
• Drive Mode: Exposure Bracketing, 3 frames in 1/3 EV steps

Except for the bracketing order, there is not much in this setup that unusual.

To see what I saw with the FA 35/2*

• In Av mode, set the aperture to f/2.8 (one stop down from full open)
• Switch to M mode and note that f/3.2 is now the set aperture. Don't be alarmed. F/3.2 is intentional and expected.
• Move the aperture e-dial one click to widen the aperture 1/3 stop to f/2.8. Cool! It worked!
• Move the aperture e-dial one click back to narrow the aperture 1/3 stop to f/3.2 again. Note that it says f/3.5, not f/3.2.
• Move one more click narrower and note that 2/3 stops from f/2.8 is now f/4.5. Move one step again and see that f/5.6 is now 1 stop (3 steps) above f/2.8. The magic continues if one keeps rotating the dial.
• Now lets step back down and magically f/5.6 is two stops (6 steps) above f/2.8 like it is supposed to be.

Are we amazed yet or is it just me with my camera? If not reproducible, it may be time for me and/or my camera to see a specialist. If y'all see the same, then we have a vexing behavior that some might call a "bug".

But wait! There's more!!

• Move the set aperture two steps wider from f/2.8 to f/2.2. The ability to do so should raise a few alarms since f/2.2 may not work properly for a three frame bracket in 0.3 EV steps. It all depends on which step it is. If it is the "-" step (narrowest opening in the series) we have a problem.
• Expose the full bracket series of three frames
• Be amazed to see a series of three with the last two frames (0.0 EV and +0.3 EV) with the same settings (+0.6 EV more light than the first frame)

I stopped exploring at this point and decided I had found enough vexation for one day.

The Work-Around(s)

• Changing the bracket order to "0 - +" or "0 + -" will correct the problem of improper e-dial EV steps
• Changing the green button action from "Program Line" to "Tv-shift" will also correct the EV step issue and does so in a fairly intuitive way consistent with the notion of manual exposure control. Update: I did some additional inquiry with firmware v1.30 and found that this workaround also mitigates the bad bracket set problem.
• I could not find a work-around for the bad bracket set problem

Comments, confirmations, and refutation are all encouraged and appreciated

Edit: After reviewing the first group of comments, it occurred to me to simply state the issues in terms of the implied "contract" of the camera with its user. The broken contract rules are as follows:

• The e-dial does not consistently increment/decrement aperture in 1/3rd stop steps as per system settings
• The system does not properly bracket exposure (EV) when the set aperture is within one bracket step of the lens maximum aperture.

/Edit

Steve

* The actual lens is not pertinent except that the description assumes f/2 maximum aperture

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Last edited by stevebrot; 04-11-2017 at 07:43 PM.

[pschlute]

Is this really a bug?

You are telling your camera to give you a 1/3 underexposure for the first of your three brackets. You have also told your camera it can decide whether to change Av or Tv to achieve this according to the program line. Each time in your example you stop down 1 click (1/3 stop) the camera is evaluating the settings and is changing the chosen exposure by 1/3. How it does this will vary according to the program line.

In your example you have moved the dial three clicks (1 stop) from f2.8 and you are expecting to see f4 I presume? But the camera is saying "oh we will use f5.6 and a 2/3 slower Tv setting to achieve the first bracket exposure".

As you yourself have noted, if you tell the camera to use Tv shift instead of program line it will not adjust your chosen Av setting. If you do the same experiment with these settings, you would notice the camera does the same adjustments (anomolies) as you move the shutter speed.

[BigMackCam]

If nothing else, if someone could check their K-3's behavior, I would be most appreciative.

I've tried it and confirmed your findings, with the FA50/1.4 on my K-3, v1.30 firmware (different apertures, obviously, to induce the same behaviour). How bizarre

[pschlute]

How bizarre

What are you expecting the camera to do when you stop down the aperture ? It seems to me the camera is doing what you have told it to do?

[BigMackCam]

What are you expecting the camera to do when you stop down the aperture ? It seems to me the camera is doing what you have told it to do?

There are two problems here. I can't improve on Steve's description of the first one:

Move the aperture e-dial one click back to narrow the aperture 1/3 stop to f/3.2 again. Note that it says f/3.5, not f/3.2.
Move one more click narrower and note that 2/3 stops from f/2.8 is now f/4.5. Move one step again and see that f/5.6 is now 1 stop (3 steps) above f/2.8. The magic continues if one keeps rotating the dial.

As for the aperture...

With my FA50/1.4 fitted and settings as per Steve's original post, I set my aperture to f/4 and take three bracketed shots. Given the selected bracketing order of "- 0 +" and 1/3EV steps, I'd expect to get shots at f/4.5, f/4 and f/3.5 respectively - but instead I get f/4, f/3.5 and f/3.2. Each shot is out by +1/3EV. Hmmm.

Now, I set my aperture to f/1.6 (the maximum it will allow with the current settings, because it needs to take the +1/3EV shot at f/1.4). I take my three bracketed shots, expecting to get f/1.8, f/1.6 and f/1.4. Instead, the first shot is at f/1.6 followed by two identical shots at f/1.4 - presumably because it can't open the lens any further than f/1.4.

The camera is incorrectly using the current aperture setting to begin the "- 0 +" sequence, instead of "current aperture minus 1/3EV". The EVs for each shot are out by one step. As a result, you get one correctly-exposed shot followed by two over-exposed, instead of one under-exposed, one correctly-exposed, and one over-exposed. Instead of shooting "- 0 +" as configured, it's shooting "0 + ++", if that makes sense?

EDIT: Hmmm. Curious. If I change my bracketing to 2 stop intervals (which I often use for HDR), it will let me set the FA50/1.4 to f/2. I would have expected the limit should be f/2.8 (to allow for bracketed shots at f/1.4, f/2.8 and f/5.6)

Oh man, if I now set the bracketing to 1 stop intervals, it lets me set the aperture to a max of f/1.8 (not f/2 as expected)... then, when I turn the aperture e-dial, on the first click it changes from f/1.8 to f/2, on the second click the aperture value doesn't change but the exposure does, one the third click it changes to f/2.8. On the way back, first click takes me to f/2.5, second click to f/2, third click aperture stays the same but exposure changes, fourth click back to f/1.8

I'm also going to stop for now... This is perplexing... Perhaps I'm misunderstanding how this works...

[UncleVanya]

Rather than report just the aperture could you provide the complete exposure triangle? I wonder if the shutter speed or ISO settings have been manipulated by the camera during the bracketing? I think that is what pschlute is asking. I am unclear myself about the expected behavior. On the surface it seems off.

[pschlute]

The camera is attempting to provide 3 shots at -1/3 ; 0 ; +1/3

Unless you change the setting in-camera telling it to shift the Tv, the camera will make its own mind up how it achieves the - and + exposures and will do so according to the "program line". You are mistaken in thinking it will simply shift the aperture for each exposure, unless you change the setting that tells it not to use program line.

On the k1 this is achieved by changing the behavior of "green button in manual mode" from program line to Tv or ISO shift.

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Last edited by pschlute; 03-27-2017 at 06:35 AM.

[BigMackCam]

Rather than report just the aperture could you provide the complete exposure triangle? I wonder if the shutter speed or ISO settings have been manipulated by the camera during the bracketing? I think that is what pschlute is asking. I am unclear myself about the expected behavior. On the surface it seems off.

Sure, no problem:

Same bracketing order as before: "- 0 +"
Exposure racketing 3 shots with interval of 1/3EV
M mode
Shutter 1/100s
Aperture f/4.0
ISO 1000 (manually set, not Auto)
Not using green button

Three bracketed shots:

Shot #1: 1/100s, f/4.0, ISO 1000 (shows as -0.3 EV comp)
Shot #2: 1/80s, f/3.5, ISO 1000 (shows as 0.0 EV comp)
Shot #3: 1/80s, f/3.2, ISO 1000 (shows as +0.3 EV comp)

Hang on... I think I get this now... Because of the bracketing order, maybe the selected aperture setting represents the "-" shot. So that might actually working correctly. But if that's the case, why won't it let me open the lens to maximum aperture (it'll only let me go to f/1.6 with these settings, not f/1.4)... OK, I understand now. It works

[BigMackCam]

The camera is attempting to provide 3 shots at -1/3 ; 0 ; +1/3

Unless you change the setting in-camera telling it to shift the Tv, the camera will make its own mind up how it achieves the - and + exposures and will do so according to the "program line". You are mistaken in thinking it will simply shift the aperture for each exposure, unless you change the setting that tells it not to use program line.

On the k1 this is achieved by changing the behavior of "green button in manual mode" from program line to Tv or ISO shift.

Thanks for this. OK, so I've actually disabled the Green Button for M mode, and re-taken the same sequence of shots. I now get:

Shot #1: 1/100s, f/4.0, ISO 1000 (shows as -0.3 EV comp)
Shot #2: 1/100s, f/3.5, ISO 1000 (shows as 0.0 EV comp)
Shot #3: 1/100s, f/3.2, ISO 1000 (shows as +0.3 EV comp)

[stevebrot]

Rather than report just the aperture cannyou look at the complete exposure triangle? Have the shutter speed or ISO settings been manipulated by the camera during the bracketing? I think that is what pschlute is asking. I am unclear myself about the expected behavior. On the surface it seems off.

Excellent point. That is why I stipulated fixed ISO in the instructions.* It is important to consider the EV within the context of the full exposure triangle, not just the aperture, when evaluating whether the bracketing is working correctly. The expected behavior is hard to describe. I was saving the details for another post, but the simplified version goes as below. Exposure is expressed as EV** rather than going into actual setting details.

For bracket order = "- 0 +" with three frames @ 0.3 steps at fixed ISO:

• Three exposures
• #1 at -0.3 EV from #2
• #2 with 0.0 EV correction (this is the base for the bracket)
• #3 with +0.3 EV from #2

In my example, what I got was

• Three exposures
• #1 labeled as -0.3 EV compensation, but with actual EV the same as #2
• #2 labeled as 0.0 EV with actual EV assumed to be the base for the bracket
• #3 labeled as +0.3 EV compensation with actual EV +0.3 from #2

Does this make sense?

BTW: Can you do me a favor and check your K-3 to see if "one-push" bracketing is always present regardless of menu setting? Mine does that and I need to know if my camera is flipping out on me. Thanks in advance :) Edit: I figured it out...


Steve

* Since this is M-mode, ISO is always fixed or at least it should be.

** The formal definition of Exposure Value (EV), as used here, is simply the amount of exposure (x time at y aperture) and is independent of sensitivity. When qualified by sensitivity (e.g. EV400 for ISO 400) EV can also be used as a rough expression of light conditions. For example, "The meter is sensitive to -3 EV." If ISO is not explicitly defined and usage is related to light strength (not exposure), convention is to assume EV100.

[stevebrot]

In your example you have moved the dial three clicks (1 stop) from f2.8 and you are expecting to see f4 I presume? But the camera is saying "oh we will use f5.6 and a 2/3 slower Tv setting to achieve the first bracket exposure".

This is in M-mode (see thread title and description of bug). Three steps of the e-dial should be one stop difference in aperture, not two.


Steve

[UncleVanya]

Note that the example given above shows shutter speed varied which changed the exposure to fit. Can you check yours also.

[stevebrot]

EDIT: Hmmm. Curious. If I change my bracketing to 2 stop intervals (which I often use for HDR), it will let me set the FA50/1.4 to f/2. I would have expected the limit should be f/2.8 (to allow for bracketed shots at f/1.4, f/2.8 and f/5.6)

Oh man, if I now set the bracketing to 1 stop intervals, it lets me set the aperture to a max of f/1.8 (not f/2 as expected)... then, when I turn the aperture e-dial, on the first click it changes from f/1.8 to f/2, on the second click the aperture value doesn't change but the exposure does, one the third click it changes to f/2.8. On the way back, first click takes me to f/2.5, second click to f/2, third click aperture stays the same but exposure changes, fourth click back to f/1.8

I'm also going to stop for now... This is perplexing... Perhaps I'm misunderstanding how this works...

I feel your pain...I have been there

How I believe it works is far from direct and is related to both bracket order and the green button action in M-mode. If I have the intended behavior straight, part of what you are seeing is expected and part is not. I will try to explain in a few points:

• The EV you set (shutter/aperture) is the first EV in the bracket and may not be the base exposure
• The base exposure for the bracket is the frame labeled as "0.0" EV (on review) and may not reflect the shutter/aperture you chose
• The EV you set will only be the base exposure when the bracket order is "0 - +" or "0 + -"

Is the rabbit hole deep enough yet? I am so glad M-mode does not support auto-ISO


Steve

[BigMackCam]

How I believe it works is far from direct and is related to both bracket order and the green button action in M-mode. If I have the intended behavior straight, part of what you are seeing is expected and part is not. I will try to explain in a few points:

• The EV you set (shutter/aperture) is the first EV in the bracket and may not be the base exposure
• The base exposure for the bracket is the frame labeled as "0.0" EV (on review) and may not reflect the shutter/aperture you chose
• The EV you set will only be the base exposure when the bracket order is "0 - +" or "0 + -"

Is the rabbit hole deep enough yet?

I've just figured this out and was about to post again when I saw your reply.

Yes, I agree with the above. If we accept that as fact (if not exactly obvious nor common sense!), what confuses me is that in "- 0 +" bracketing order, and with the green button configured to Av Shift or "--" (disabled), the maximum aperture setting allowed is just one bracketing interval down from wide open - so, f/1.6 on my FA50/1.4. The result, then, of shooting at that aperture setting is the "-" shot at f/1.6, the "0" shot at f/1.4, and the "+" shot also at f/1.4 and the same shutter speed (identical to the "0" shot). It seems that if we're right about the way it's working, with "- 0 +" ordering, the camera should impose a maximum aperture setting *two* intervals down from the lens's maximum - so, f/1.8 in this instance - in order to take shots at f/1.8, f/1.6 and f/1.4.

Does that make sense, or am I getting confused again?

[stevebrot]

Thanks for this. OK, so I've actually disabled the Green Button for M mode, and re-taken the same sequence of shots. I now get:

Shot #1: 1/100s, f/4.0, ISO 1000 (shows as -0.3 EV comp)
Shot #2: 1/100s, f/3.5, ISO 1000 (shows as 0.0 EV comp)
Shot #3: 1/100s, f/3.2, ISO 1000 (shows as +0.3 EV comp)

Now do it with a set aperture of f/1.6.


Steve