Depth of Field in "Auto" Shooting Mode

My wife shoots with the D7000. We were on a 17' fiberglass powerboat (e.g. moving a little), and she was photographing a sailboat race (e.g. moving subjects). When reviewing one of her photos that she would have liked, she saw that one boat/crew was in focus and the other blurred (depth of field issue). To understand, we reviewed the parameters, which were: ISO800, f6.3, 1/2500sec, 170mm (lense was VR 18-200). Here is the question: The "Auto" shooting mode obviously selects shutter speed and f-stop, but why would it fix f6.3 (limited depth of field) and take shutter speed way up higher than really ever necessary? Does anyone on the forum understand the "Auto" feature well enough to explain? Later she tried to shoot at a shutter speed of 1/250sec but then her Auto Focus mode somehow changed and she had a lot of out of focus photos. We have reviewed the manuals and can find no explanation. HELP!

Dave in IL

Dave_IL said:

My wife shoots with the D7000. We were on a 17' fiberglass powerboat (e.g. moving a little), and she was photographing a sailboat race (e.g. moving subjects). When reviewing one of her photos that she would have liked, she saw that one boat/crew was in focus and the other blurred (depth of field issue). To understand, we reviewed the parameters, which were: ISO800, f6.3, 1/2500sec, 170mm (lense was VR 18-200). Here is the question: The "Auto" shooting mode obviously selects shutter speed and f-stop, but why would it fix f6.3 (limited depth of field) and take shutter speed way up higher than really ever necessary? Does anyone on the forum understand the "Auto" feature well enough to explain? Later she tried to shoot at a shutter speed of 1/250sec but then her Auto Focus mode somehow changed and she had a lot of out of focus photos. We have reviewed the manuals and can find no explanation. HELP!

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I know when in full Automatic mode the camera will keep the ISO sensitivity under ISO 800 until an aperture and shutter speed combination will not give it a good exposure. Then it will increase the ISO sensitivity to get correct exposure. What baffles me is why it went with such a high ISO to begin with; because this is what "forced" the medium-ish f/6.3 aperture and crazy high shutter speed. I do know the CPU in your camera, when metering shots, uses a database of "photos" stored in memory that it analyzes to compute exposure and while this works most of the time, I have to wonder if you didn't manage to throw it some kind of "curve ball". It's one of those things you risk when you fly on "auto pilot".

While I may not know precisely what happened, I think the simplest solution to the problem would be go to "A"perture Priority mode so you can wrest back some control over how you expose your shots in the future with full control over depth of field.

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Thanks for responding. Interesting comment about the CPU analyzing stored photos. We will experiment with Aperture priority mode. After the focus issue in Shutter priority mode, she isn't too eager to try anything while important, but we can play around when it isn't critical. Just so long as shutter speed is high enough to negate the motion of all the boats including ours.

Forgot: The ISO 800 setting was our fault -- it was left unchanged from some low-light photos she took. For the daylight shots she should have set it back to 100 or 200.

Depending on our experiments, we may be back asking about the Auto Focus system. Thanks again for the response.

Dave_IL said:

Thanks for responding. Interesting comment about the CPU analyzing stored photos. We will experiment with Aperture priority mode. After the focus issue in Shutter priority mode, she isn't too eager to try anything while important, but we can play around when it isn't critical. Just so long as shutter speed is high enough to negate the motion of all the boats including ours.

Forgot: The ISO 800 setting was our fault -- it was left unchanged from some low-light photos she took. For the daylight shots she should have set it back to 100 or 200.

Depending on our experiments, we may be back asking about the Auto Focus system. Thanks again for the response.

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Having your ISO manually set to 800 explains the crazy fast shutter speed then so that mystery is solved...

Based on your posts here's how I suggest you set your camera settings: Select Aperture Priority Mode. In the menus turn on the "Auto ISO" option and let it go from ISO 100 to ISO 6400 (or whatever the maximum ISO is for your camera). While in the Auto ISO menu, set your minimum shutter speed to 1/250. For your autofocus settings use AF-A with D21.

With those settings the operator chooses the aperture to control depth of field. The camera will automatically adjust the ISO to keep the shutter speed at, or above, 1/250 for a decent degree of motion freezing. If you want more stop action, increase the minimum shutter speed in the Auto ISO menu but know that you're doing so at the cost of a shallower depth of field, or a higher ISO and the noise that can come with it. I find the D7000 does just fine shooting at ISO 800 and it's only around 1600 or so that I really start to notice the digital noise. Some people are fine with more noise, some want less; it's a personal choice sort of thing. My main point, though, is that I'd much rather have "nailed the shot" at a noisy ISO than to have missed it altogether or have a shot ruined by motion blur. You can remove a lot of digital noise in post processing, motion blur not so much.

The suggested auto-focus settings will allow the camera to intelligently switch between AF-S for stationary subjects and and AF-C for moving subjects. The D21 will use 21 focus points to track moving subjects quickly. You could use more focus points but since boats move on a more or less predictable path, using 21 points will decrease the time required to achieve focus lock while still using enough points to accurately track a predictably moving subject with minimum focus-lock times.

Try those settings perhaps and adjust as needed. Practice is always good so you get used to the controls and making adjustments quickly.

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In Auto mode (or perhaps just Program) it is possible to use one of the command dials to cycle through various combinations of correct exposure, so if DoF is a concern and your wife knows enough about what to look for then she can use this option.


Auto is a dicey setting and it's best to avoid it because of things like you've experienced. You can set up an "intelligent" auto in other modes. I highly recommend using Aperture Priority in combination with Auto ISO and setting your minimum shutter speed to whatever is appropriate for the situation. Setting it to Auto has the camera set it based on focal length and you have the ability to then set it "Faster" or "Slower" from a middle point (which guarantees Shutter Speed will be one click above focal length). If you're outdoors and dealing with moving targets you can set it to make sure that it never goes below, say, 1/250s. You can also cap the ISO at whatever level keeps the noise manageable (about 1600 on the D7000).

These are really good responses, Horoscope Fish & BackdoorHippie (love those monikers!). Found and set the Aperture priority Auto ISO settings. Had to put it down for a while, but next is the Auto Focus setting. Sounds like this is what we need. Thanks again for the advice.

Well, we are back again. The Aperture priority setting looks like it will provide better control over depth of field, and the AutoISO feature does indeed keep exposure in line by varying ISO as needed.

HOWEVER, now we are having problems with focus. We have tried several settings, starting with the one recommended by Horoscope Fish. No dice. BTW we are also experimenting with my 800E so we understand both cameras. Same problem with both. Our test photos are of stationary objects, so we switched to AF-S and tried various combos of focus points. Neither AF-C nor AF-S have yielded even good results. Can you help us understand the relationship in how the focus system works on "Auto" as opposed to A or S modes?

Wife is getting frustrated ... Thanks!

What is the problem you are having, exactly? Can you post some examples?

Here's an explanation of the different Auto-focus Modes, Auto-focus Area-Modes and so forth: DSLR Auto-focus Modes Explained

Dave_IL said:

Well, we are back again. The Aperture priority setting looks like it will provide better control over depth of field, and the AutoISO feature does indeed keep exposure in line by varying ISO as needed.

HOWEVER, now we are having problems with focus. We have tried several settings, starting with the one recommended by Horoscope Fish. No dice. BTW we are also experimenting with my 800E so we understand both cameras. Same problem with both. Our test photos are of stationary objects, so we switched to AF-S and tried various combos of focus points. Neither AF-C nor AF-S have yielded even good results. Can you help us understand the relationship in how the focus system works on "Auto" as opposed to A or S modes?

Wife is getting frustrated ... Thanks!

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You need to post a few images with EXIF data so we can be more helpful.

Same problem with both

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I'm suspecting some sort of operator error over equipment failure.

Blacktop said:

I'm suspecting some sort of operator error over equipment failure.

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Agreed.

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Yes, am re-reading the article. Will try to post an image. Thanks for the continuing help.

Dave

Site will not let me upload the ".nef" image, so you can see details as well as the focus system used. How do I do this?

Thanks, Dave

PS - My wife has taken thousands and thousands of photos on "Auto" and never had a focus issue, just the depth of field we started with. Something has changed in the focus system when we go to "A" mode.

Please advise and thanks again.

Dave_IL said:

Site will not let me upload the ".nef" image, so you can see details as well as the focus system used. How do I do this?

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You can't upload a .NEF file, you have to save it as a .JPG and upload that.

Dave_IL said:

Something has changed in the focus system when we go to "A" mode.

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Once the Auto-focus Mode and Auto Focus Area Mode settings are dialed in, they don't change until you go in and change one or the other; switching between Exposure Modes (P, S, A, M and Auto) does not alter the auto-focus settings in any way.

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Okay, here goes it. First is the photo as jpeg, second is screen print of ViewNX2 showing focus system used and what the software thinks is the focal point. The photo is not too bad but not nearly as sharp as it should be. Wife says the viewfinder showed more than 1 "focus box" and can't say they were logically arrayed. In our tests, we saw lots of focal points in ViewNX2 that were not even close to in the same plane. Finished reading the article for about the third time. Mansurov has a good explanation but it is by necessity general and does not specifically go into how you set the camera. We have read the manual several times and experimented with the Auto Focus button and dials. We think it is possible to select stuff that is not compatible and confuses the camera (not to mention us). In some cases, the camera does not display ANY "focus boxes" in the viewfinder and we have no idea what it is choosing to focus upon (and not surprisingly the photo is completely out of focus). Obviously we need some help or references that explain specific settings. One thing we may do, is go to our local camera shop (bought the D7000 there) and seek their help. Not sure they know more than you do, though. Thanks for sticking with us.

Once the Auto-focus Mode and Auto Focus Area Mode settings are dialed in, they don't change until you go in and change one or the other; switching between Exposure Modes (P, S, A, M and Auto) does not alter the auto-focus settings in any way.

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This is interesting, as her camera did not do this. She shot for two days in Auto mode with AF set to Auto-AF and Auto point select. No focus issues, just the depth of field we started with.

After observing the really high shutter speed with middling f-stop, for the next day I had her change to Shutter priority of 1/250 (enough to freeze motion and eliminate movement on our boat and/or hand shake) which would force (on bright days) a better f-stop. We did not change anything in the AF system. The next day, almost all (but NOT all) her shots were out of focus and she complained that the "focus boxes" seen the day before were no longer visible in the viewfinder. I was in hot water, so she changed back to Auto mode and focus was as before. This leads me to question either your statement or the performance of our D7000. The manual seems to agree with your statement as does other stuff I have read. Comment? Has anyone verified that it works that way?

PS - As part of this quest, I updated her camera to the latest firmware version (A-1.03 & B-1.04). No mention of focus in them but just better to be up-to-date.

Another aside - I do not usually shoot in Auto mode with my D800E, and have had focus problems (why I previously read the Mansurov article). So I wonder if this goes across different cameras? Maybe it is in the settings?
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New information: I found a reference which introduced the "AF Custom Settings" choices. It is in the "Custom Settings Menu" (pencil icon). There were a couple of settings which contributed to our confusion.

Setting a1 which is AF-C priority was set to "Shutter" meaning it would take a photo upon shutter release whether it was in focus or not. Changed the setting to "Focus" meaning the photo would not be taken until focus was achieved.

Setting a4 which is "AF point illumination" was set to "Off" meaning the camera would NOT illuminate the focal point in the viewfinder (one of our specific problems). Set it to "On" so we will know the focal point.

All the other settings seemed okay to me. We ignored this part of the manual because we didn't think we needed to make "custom" settings. Wrong! We will see how this works in further tests. Fingers crossed.