D7100 Issues with Aperture Priority Mode

[Don Kuykendall_RIP]

Generally Matrix, unless I'm doing moon shots, where I use Spot. I did have a recent episode where I forgot to switch back to Matrix from Spot and got squirly results on the venerable 35 f1.8 DX, and have learned to watch the metering mode ever since


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Matrix can be a little erratic at times. I generally use the center weighted metering and have had very good luck with it. You might give it a try.

 

[gustafson]

Matrix can be a little erratic at times. I generally use the center weighted metering and have had very good luck with it. You might give it a try.

That is useful to know, I will try center weighted. Is there a setting you use with center (i.e. the size of the center circle, which I believe one can set on the D7100)?


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[Don Kuykendall_RIP]

That is useful to know, I will try center weighted. Is there a setting you use with center (i.e. the size of the center circle, which I believe one can set on the D7100)?


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I don't remember exactly what the sizes are on the D7100. I have not looked at them in a while. If I remember correctly there are 2 different sizes? Try the larger one first and see how it works and then change over and shoot the same set of photos with the smaller size. Shoot quite a few in each setting so you get a good feel for how it works.


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[Nikos_St]

8mm is the default one.

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[Pretzel]

Here's a link to some of the problem pics. The photos that appear to be taken by a 70-210 f/4 @ 145mm were in fact taken with a modified TC-16a fitted with a 200 f/4 Q.C or 100 f/2.8 E or some other manual focus lens (I don't own a 70-210 f/4 and my D7100 has never had one mounted on it). Thank you for review and comments.

https://www.flickr.com/gp/89411942@N04/Z389m3

Ahh, can't view flickr from work, so will look when I get home. It it displaying the EXIF with the pics?

 

[gustafson]

Ahh, can't view flickr from work, so will look when I get home. It it displaying the EXIF with the pics?

It is for me, but you may have to view on a desktop and scroll down below the image for EXIF options. Let me know if you're unable to see EXIF data. I wasn't able to tell from the EXIF which exposure priority mode was being used, however, so some of the photos might be in modes other than Aperture Priority.


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[cwgrizz]

The D7100 has Center Weighted choices of 6, 8, 10, 13mm and Average. FYI

 

[gustafson]

The D7100 has Center Weighted choices of 6, 8, 10, 13mm and Average. FYI

I did see that this morning, thanks for sharing! Also, the help info indicates that for non-CPU lenses, 8mm is the only option.


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[Pretzel]

It is for me, but you may have to view on a desktop and scroll down below the image for EXIF options. Let me know if you're unable to see EXIF data. I wasn't able to tell from the EXIF which exposure priority mode was being used, however, so some of the photos might be in modes other than Aperture Priority.


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I can tell you the most glaring thing that I see right now... the shutter speed on quite a few of 'em at 1/13 at 55mm focal length. At 55mm, even with VR, you should be shooting at a BARE minimum of 1/25 shutter speed, but I'd recommend nothing slower than 1/50. Shutter speed should equal out to your focal length for most handheld shooting, TBH. Any lower, and you run the risk of hand shake, no matter how steady you feel, and it's that hand shake that I'm seeing in most of the pics. Either that, or the lovely youngster is moving a bit, and 1/13 just isn't gonna freeze your subject.

The outside shots are the same, focal length of around 150mm, but a 1/50 shutter speed. Not only a bit of hand shake, but overexposed, as 1/50 is quite the long exposure for a beach scene, even at ISO 100 and f11. The one of the Febreze is at 150mm but 1/8 sec... ouch! Minimum shutter speed of 1/150 there, again matching the focal length is a bare minimum. Aperture mode doesn't know how you're shooting, whether it's handheld or tripod, or whether your model is moving or not. It's just taking the aperture given, the ISO available, and setting a shutter speed to allow for proper light exposure (if possible), but it doesn't mean it's always going to choose the correct shutter speed. Keep an eye on the shutter speed in your viewfinder, and if it's slower than 1/xxx (xxx being your current focal length), either open up the aperture or increase the ISO to get it higher for these types of shots. (EDIT: Or add light - flash, overhead, etc. BTW, for portraits and single subject shots that are non macro, f4 works well).

On the pool shots outside, you were at ISO 800, which is way too high for an outdoor daytime shot, too. Overall, I think a solid understanding of the exposure triangle (especially shutter speeds as compared to focal length of the lens) is gonna help you greatly with focus, exposure, etc.

 

[gustafson]

@Pretzel, thanks for the detailed review and feedback! Your observations are spot on. Before I got the D7100, I was using manual lenses on my D3300 in M mode (the only mode that is allowed on that body). As the D7100 allows using the A mode for Ai and Ai-s lenses, and after learning that a lot of seasoned photographers shoot in A, I've been primarily shooting in that mode. I admit that I don't completely understand how auto ISO works, because I generally set mine to Max 6400 with a minimum shutter speed of 1/125, but looks like those are untenable constraints for the slower lenses that I'm using, and the the ISO is maxing out but the corresponding shutter speed is still too slow.

It just occured to me that I should do a side-by-side test with my 18-55 VR lenses mounted on the D7100 and D3300 in A with the same auto ISO settings.

Thanks again for your insights!


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[Marcel]

One thing that came to mind after seeing your pics on Flickr is the fact that the pictures with max aperture (5.6) are OK while the more you close the more overexposed they become. I've seen this situation when the aperture blades become a bit sticky and slow. The meter expects the blades to be completely closed to the selected aperture but when you press the shutter they never get that far.

To check for this problem, put the camera on a tripod, take a few shots with different apertures with auto iso OFF, start with the larger diaphragm going to the smaller and then compare your shots' exposure. If you see the histogram going more and more to the right, it means that your blades are getting sluggish and it's the problem you have to face.

Keep us informed and good luck.

 

[gustafson]

Thanks @Marcel! Brilliant suggestion, wouldn't have even thought of trying that.

I did do the side-by-side test with the D7100 and D3300 with 18-55 VRs (one older and one VR II) in aperture priority and while the results weren't identical, they were generally close enough to conclude that there isn't a glaring problem with my D7100. Will post pics later today. It could be that some of my older manual lenses have an aperture issue, and / or perhaps there's an issue with the TC-16a AI indexing mechanism. Thanks for the tip on what to look for and how!


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[gustafson]

Here's a link to a Flickr set comparing the D3300+18-55VRII vs. D7100+18-55VR. Its a bit of an apples to oranges comparison due to the differences in the exposure capabilities of the cameras, and the fact that the lenses, albeit similar, are of different generations. Most of the shots were wide open (f5.6 @ 55) with AF and VR activated, and are unprocessed JPGs. There isn't a marked difference in the exposure performance of the two setups, although to my eyes, the D3300+18-55VRII shots just seem a tad better exposed and more pleasing aesthetically. I'd be interested to hear what others think. I've arranged the pics in pairs where the first is with the D7100+18-55VR setup, and the second is with the D3300+18-55VRII setup.

https://www.flickr.com/gp/89411942@N04/zL2N69

 

[gustafson]

Went and read up on auto ISO, and while it helped, I still have some confusion about how it works.

Understanding Auto ISO | Changing ISO on the Fly from Nikon

On one hand, Nikon states "Although most Nikon digital cameras with Auto ISO allow you to use the feature in all shooting modes—Program, Aperture Priority, Shutter Priority, Manual, Scene modes—the effects may be more noticeable when you’re in Manual or Shutter Priority modes." and "In Aperture Priority, the aperture value is set by the user and the shutter speed value is determined by the camera system. If light levels change and the shutter speed required to achieve the correct exposure is beyond the shutter speed range of the camera, ISO Auto will increase the sensitivity. *As the shutter speed range of a D-SLR is very large, it is rare that a shutter speed beyond the range of the camera (i.e. 30 sec) will occur under normal lighting conditions.", which suggests that using Auto ISO in Aperture Priority is of no use.

On the other hand, it also states that "Within the Auto ISO settings, you can also set the minimum shutter speed where this “jump” to a higher ISO will occur. If you are don't mind handholding the camera to 1/60 sec. shutter speed, set that as the minimum shutter speed. Want to minimize the possibility of camera shake—then set the minimum shutter speed to 1/250 sec. The Auto ISO feature tells the camera to change the exposure based on the changing light. As the light in the scene dims, the shutter speed will drop to let in more light, to ensure a correct exposure. When it hits the "minimum" shutter speed that was set, the ISO increases to keep the exposure correct."

My expectation has been along the lines of the previous statement, viz. the D7100 in A mode will first tweak the shutter speed at the current ISO setting, and raise ISO only when it reaches the minimum shutter speed. But I don't think that has been my experience, as I believe the camera lets me take shots in A mode at speeds slower than my specified minimum. Will confirm this and report back, but would be interested to hear if that would be considered normal behavior of the Auto ISO feature.

 

[Spottydumplings]

My expectation has been along the lines of the previous statement, viz. the D7100 in A mode will first tweak the shutter speed at the current ISO setting, and raise ISO only when it reaches the minimum shutter speed. But I don't think that has been my experience, as I believe the camera lets me take shots in A mode at speeds slower than my specified minimum. Will confirm this and report back, but would be interested to hear if that would be considered normal behavior of the Auto ISO feature.

This is my experience of how it works; however, if the camera reaches the Auto ISO limit i.e. it will not raise the ISO above this, then it will start to lower the shutter speed to give the required level of exposure.

 

[gustafson]

This is my experience of how it works; however, if the camera reaches the Auto ISO limit i.e. it will not raise the ISO above this, then it will start to lower the shutter speed to give the required level of exposure.

Thanks, that helps! So essentially, if exposure requirements in Auto ISO mode require the camera to violate the max ISO setting and /or the min shutter speed setting, it will violate the min shutter speed setting every time.

Seems like a better approach for Aperture Priority in these challenging exposure situations is to avoid using Auto ISO and to manually raise the ISO if the shutter speed falls below your threshold. Or if you can afford it, get faster lenses


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[gustafson]

One thing that came to mind after seeing your pics on Flickr is the fact that the pictures with max aperture (5.6) are OK while the more you close the more overexposed they become. I've seen this situation when the aperture blades become a bit sticky and slow. The meter expects the blades to be completely closed to the selected aperture but when you press the shutter they never get that far.

To check for this problem, put the camera on a tripod, take a few shots with different apertures with auto iso OFF, start with the larger diaphragm going to the smaller and then compare your shots' exposure. If you see the histogram going more and more to the right, it means that your blades are getting sluggish and it's the problem you have to face.

Keep us informed and good luck.

@Marcel, I performed your test as suggested with a few manual and AF-S lenses and found that the histogram more or less stayed put on stopping down. However, when using these lenses with the modified TC-16a, the histogram did move appreciably to the right, between 1/3 upto 1EV per aperture stop!! This has been a big learning, and I guess I'll have to apply adequate exposure compensation if stopping down lenses when they're mounted on my TC-16a unless I can fix the TC itself from behaving this way.


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[Spottydumplings]

Thanks, that helps! So essentially, if exposure requirements in Auto ISO mode require the camera to violate the max ISO setting and /or the min shutter speed setting, it will violate the min shutter speed setting every time.

Seems like a better approach for Aperture Priority in these challenging exposure situations is to avoid using Auto ISO and to manually raise the ISO if the shutter speed falls below your threshold. Or if you can afford it, get faster lenses

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That's what I have seen every time that I have used it.

Essentially you would be manually doing what the camera is doing automatically; unless when you reach your max acceptable ISO and min shutter speed you are willing to under exposure your shots and try to compensate in post processing - which could introduce more noise than just accepting a higher ISO in camera. As you say you could always go with faster glass:greedy_dollars: OR if the situation allows you could try introducing more light into the scene.

 

[Marcel]

@Marcel, I performed your test as suggested with a few manual and AF-S lenses and found that the histogram more or less stayed put on stopping down. However, when using these lenses with the modified TC-16a, the histogram did move appreciably to the right, between 1/3 upto 1EV per aperture stop!! This has been a big learning, and I guess I'll have to apply adequate exposure compensation if stopping down lenses when they're mounted on my TC-16a unless I can fix the TC itself from behaving this way.


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I used to have an extension tube that would act this way with a certain lens. That's how I found out this could be a problem. The main thing is you can't rely on exposure compensation when you close the aperture because it can react different avery time (sticking more or less depending on temperature for example). Maybe stop using the converter... with that lens anyway. Have you tried it with other lenses?

 

[gustafson]

I used to have an extension tube that would act this way with a certain lens. That's how I found out this could be a problem. The main thing is you can't rely on exposure compensation when you close the aperture because it can react different avery time (sticking more or less depending on temperature for example). Maybe stop using the converter... with that lens anyway. Have you tried it with other lenses?

Yes, I tried the modded TC with a couple of lenses, and it doesn't appear to be a case of a sticky aperture as much as an artifact of one aspect of the TC mod itself, which fools the camera into thinking a 70-210 F4 CPU lens is attached (not doing so results in less desirable behavior, such as inability to control aperture from the camera body, and a constant aperture reading of F/1). I haven't been able to isolate why this results in the aberrant exposure behavior, but it is reproducible. I need to play with the D7100 settings to see if I can get correct metering with the modded TC with manual lenses in A mode, but its a great help to have identified the issue to begin with. Thank you!