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AF in low light is sometimes lazzy
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Aug 15, 2021 06:54:04   #
Dan' de Bourgogne
 
Last night I had sometimes hard time to get sharp images.
I took a whole bunch of pictures in "Abbaye de Fontenay"...a beautiful place...part of it is a private property, the abbaye itself and lot of its surrounding area is "domaine national" (monuments historiques).
About 50% of the pictures ended out quite blurry.

Problem is: low light...so AF not accurate. As I have to wear a mask, I get instantly fog on my glasses (hot wheather and humid air): difficult to adjust manually sharp focus.
Is there a way to improve the "sensitivity" of the AF , making it more accurate in low light?


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Aug 15, 2021 07:07:44   #
tcthome Loc: NJ
 
Have you tried live view & focusing manually with the lens? I know , not AF which you asked about ... I seen someone in a video turn the ISO way (helps the camera see better it seems)up to focus & lower it back to the desired ISO after focusing. they didn't show the screen or view finder so. Haven't tried it yet but will in the future sometime just to see if it works.

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Aug 15, 2021 07:23:36   #
CO
 
I have the same lens - the Nikon 16-85mm f/3.5-5.6. I see with the first photo you had the focal length at 16mm, the aperture at f/11, the ISO at 100, and the shutter speed was 1.3 seconds. 1.3 seconds is much too long to hand hold the camera. The fifth photo has a 4 second long shutter speed. Were you hand holding the camera or was it on a tripod? I see ghost images of people walking through the scene. You should have had the ISO higher and used a larger aperture setting to produce a faster shutter speed. Also, the focusing mode is on AF-C. That should have been AF-S for static subjects.



People walking through the scene are ghost images and shutter speed is too slow for hand holding
People walking through the scene are ghost images ...

The fifth photo has a 4 second long exposure.
The fifth photo has a 4 second long exposure....
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Aug 15, 2021 08:35:31   #
Dan' de Bourgogne
 
tcthome wrote:
Have you tried live view & focusing manually with the lens? I know , not AF which you asked about ... I seen someone in a video turn the ISO way (helps the camera see better it seems)up to focus & lower it back to the desired ISO after focusing. they didn't show the screen or view finder so. Haven't tried it yet but will in the future sometime just to see if it works.


Oh Yes, thank for reply! That's an very interesting tip! So Iwill check it ...not tomorrow bu right now instead.
I come back soon. BTW: Nikon D7200+Nikkor DX 16-85 mm.
Keep "tuned".

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Aug 15, 2021 09:09:32   #
CHG_CANON Loc: the Windy City
 
CO gave an excellent analysis and impact of your exposure parameters and how they negatively impacted your results. You asked about AF, an additional tip is to find something of 'contrast' in your image. Take the first vertical image in your selection. There's a candle on a shelf in the details of the arch. Using a single AF point selectively set on that candle and / or where the arch meets the sky gives your camera something of high contrast to assist the AF.

I don't want to come down 'hard on you', but I do want to correct the premise of your post. These examples are not the equipment's failure. These are entirely the photographer shooing in Manual exposure. The colors of this vertical view are nice, but the image fails in the soft focus. At 8 second, f/11, ISO-100, we see opportunities for a sharper image. If you raised the ISO by 4-stops to ISO-1600, you could increase the shutterspeed to 1/20 sec, a speed you probably could handhold for a sharp(er) image at 16mm (8 sec to 1/20 sec). You also could open the aperture wider by 2-stops to f/5.6 while adjusting your ISO to ISO-800 for the total 4-stop increase in light to the sensor.

If the VR on this lens let you handhold this almost sharp vertical at 8-seconds (!!), you could leverage that knowledge to not have to get to 1/20 sec. Maybe stay slower at 1/10 sec and not bring the ISO as high or open the aperture as much.

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Aug 15, 2021 10:08:16   #
Dan' de Bourgogne
 
tcthome wrote:
Have you tried live view & focusing manually with the lens? I know , not AF which you asked about ... I seen someone in a video turn the ISO way (helps the camera see better it seems)up to focus & lower it back to the desired ISO after focusing. they didn't show the screen or view finder so. Haven't tried it yet but will in the future sometime just to see if it works.


Thank You tcthome for sharing this trick! I checked it right now...in a quite dark room (my sweety used to do her home work coz' covid)...I conveniently adjusted the exposure to get on the screen of the D7200 about the same rendering of image compared to this I saw with "nacked eyes".
First pict: 1/3" , f/4.5; ISO 100, AF activated just before hitting shutter
Secd pict: 1/100",f/4.5; ISO 3200, AF activated just before hitting shutter
Both pict shot on heavy tripod, Vibration Reduction turned OFF...

So...it doesnt bring much for AF...Note that the AF was activated pressing "back button"...but this as nothing to do with "accuracy" of focus.


3rd pict: relates to first pict...is a big crop of the area covered by the "AF square" saw in the Viewfinder
4th picet : relates to 2nd pict...is a big crop of the area covered by the "AF square" saw in the Viewfinder
Note how it becomes noisy due to higher ISO


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Aug 15, 2021 10:13:27   #
Dan' de Bourgogne
 
tcthome wrote:
Have you tried live view & focusing manually with the lens? I know , not AF which you asked about ... I seen someone in a video turn the ISO way (helps the camera see better it seems)up to focus & lower it back to the desired ISO after focusing. they didn't show the screen or view finder so. Haven't tried it yet but will in the future sometime just to see if it works.


I apologize...I forgot to mention I tried very often to set the focus manually while on tripod + setting liew view in quite big crop...Getting the sharpest possible image on screen was often very difficult because:
1) lot of fog on my "clear" glasses
2) such noisy image rendered by high ISO!

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Aug 15, 2021 10:14:47   #
CHG_CANON Loc: the Windy City
 
If you're on a tripod shooting in Live View, then feel free to be quite slow in the shutter, just being careful to not to jiggle the camera with your finger while pressing the shutter. A wired-remote is a way to avoid this human-caused shake. Or, using a 2- or 10-second delay on the shutter release.

In Live View, you can zoom the details of the image display and tell the AF to use a very small and precise location to focus. For these examples, you should be able to zoom the Live View display to show the details of the post-it so the AF point just covers this post-it, or better, the edge of the pink over the darker shadows. Hold the BBF until focus is confirmed. Release the BFF and then press the shutter button.

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Aug 15, 2021 10:21:38   #
Dan' de Bourgogne
 
CO wrote:
I have the same lens - the Nikon 16-85mm f/3.5-5.6. I see with the first photo you had the focal length at 16mm, the aperture at f/11, the ISO at 100, and the shutter speed was 1.3 seconds. 1.3 seconds is much too long to hand hold the camera. The fifth photo has a 4 second long shutter speed. Were you hand holding the camera or was it on a tripod? I see ghost images of people walking through the scene. You should have had the ISO higher and used a larger aperture setting to produce a faster shutter speed. Also, the focusing mode is on AF-C. That should have been AF-S for static subjects.
I have the same lens - the Nikon 16-85mm f/3.5-5.6... (show quote)


Thank You CO for spending time with this topic: I shot all pictures on a quite steady tripod...only the last one were shot handheld. But I discovered this afternoon while checking my DSLR I made an error: left the Vib' Réduct' left ON...while shooting on tripod...Perhaps this induced the "counter-acting" shacke?
I will take some shots...with and without "VR" to see how far it makes a difference.

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Aug 15, 2021 10:57:54   #
Dan' de Bourgogne
 
CHG_CANON wrote:
If you're on a tripod shooting in Live View, then feel free to be quite slow in the shutter, just being careful to not to jiggle the camera with your finger while pressing the shutter. A wired-remote is a way to avoid this human-caused shake. Or, using a 2- or 10-second delay on the shutter release.

In Live View, you can zoom the details of the image display and tell the AF to use a very small and precise location to focus. For these examples, you should be able to zoom the Live View display to show the details of the post-it so the AF point just covers this post-it, or better, the edge of the pink over the darker shadows. Hold the BBF until focus is confirmed. Release the BFF and then press the shutter button.
If you're on a tripod shooting in Live View, then ... (show quote)


Waouh...Mr. CHG CANON takes time for me!!!! I read everything You write because I find Your comments being very often highly interesting. OK, i shot last night most of the time on tripod...just the last picture was made handheld...the other ones were shot on tripod. Hélas...I forgot to set the lens Vib' Réduct OFF...so it remainded till this afternoon ON...Plus I shot all pict with a shutter delay 2 sec...
Of course, I tried to set the focus manually ...in LiveView with nice cropped screen...but it did'nt help the fog on glasses+ugly noisy image due to ISO 3200 (instead of ISO 100...I wanted just to get quicker shutter speed because people were running all the time in front of my lens. So I needed the shortest possible time to take one photo.)
But my question is: do You know a "trick" to make the AF get more accurate results in low light? Perhaps this is simply not possible!!!!

Now, regarding the "checking session" of this afternoon, when I shot home in low light the "home office corner" of my half...I wanted to see if the AF would make at ISO 100 a better job than when set at ISO 3200. Problem is the "heavy noise"...

All this to say: next time...tripod (even when handheld is possible)...ISO (max400 and not 3200!)...VR "off"...AF activated by BBF (was the case yesterday night)...shutter delay 2 à 4sec...(the same like yesterday night)

Hahaha...I discover just now something new!!! You write in the last sentence "Release the BFF AND THEN press the shutter button" Do You think it will give a different result if one press the BBF and while maintenig that button pressed, one hit the shutter ...delay 2 sec...shutter gets open...then closes...and finally one release the BBF? I dont remember exactly if I hold or not the BBF during all the time the picture has been taken...
Next time I will take care of this...activate shutter only after BBF has been released! Merci CHG CANON...

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Aug 15, 2021 11:04:27   #
CO
 
Dan' de Bourgogne wrote:
Thank You CO for spending time with this topic: I shot all pictures on a quite steady tripod...only the last one were shot handheld. But I discovered this afternoon while checking my DSLR I made an error: left the Vib' Réduct' left ON...while shooting on tripod...Perhaps this induced the "counter-acting" shacke?
I will take some shots...with and without "VR" to see how far it makes a difference.


What puzzled me is that everything is blurry from front to back in the photos. If focusing was off a little, there would still most likely be something in the photo that is in focus. I was thinking it was camera shake causing the blurry photos. I'm sure you will get it all straightened out with testing.

Here is something to check in the menus. Be sure that AF-C priority selection and AF-S priority selection are set to focus. If they are on release, the photo can be taken even if it has not acquired focus.



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Aug 15, 2021 11:10:44   #
CHG_CANON Loc: the Windy City
 
Dan' de Bourgogne wrote:
Waouh...Mr. CHG CANON takes time for me!!!! I read everything You write because I find Your comments being very often highly interesting. OK, i shot last night most of the time on tripod...just the last picture was made handheld...the other ones were shot on tripod. Hélas...I forgot to set the lens Vib' Réduct OFF...so it remainded till this afternoon ON...Plus I shot all pict with a shutter delay 2 sec...
Of course, I tried to set the focus manually ...in LiveView with nice cropped screen...but it did'nt help the fog on glasses+ugly noisy image due to ISO 3200 (instead of ISO 100...I wanted just to get quicker shutter speed because people were running all the time in front of my lens. So I needed the shortest possible time to take one photo.)
But my question is: do You know a "trick" to make the AF get more accurate results in low light? Perhaps this is simply not possible!!!!

Now, regarding the "checking session" of this afternoon, when I shot home in low light the "home office corner" of my half...I wanted to see if the AF would make at ISO 100 a better job than when set at ISO 3200. Problem is the "heavy noise"...

All this to say: next time...tripod (even when handheld is possible)...ISO (max400 and not 3200!)...VR "off"...AF activated by BBF (was the case yesterday night)...shutter delay 2 à 4sec...(the same like yesterday night)

Hahaha...I discover just now something new!!! You write in the last sentence "Release the BFF AND THEN press the shutter button" Do You think it will give a different result if one press the BBF and while maintenig that button pressed, one hit the shutter ...delay 2 sec...shutter gets open...then closes...and finally one release the BBF? I dont remember exactly if I hold or not the BBF during all the time the picture has been taken...
Next time I will take care of this...activate shutter only after BBF has been released! Merci CHG CANON...
Waouh...Mr. CHG CANON takes time for me!!!! I read... (show quote)


So normally, I say hold BBF with your thump and press the shutter at the same time. That is 'normally' one is not shooting in the near dark nor from a tripod. When you can work from a stable tripod platform, especially for a static subject like the abbey or your post-it tests, just focus and release the BBF. The subject is not moving, nor the camera; the focus remains where set. Then, just release the shutter.

The 2 second delay is the time between pressing the shutter and the shutter actually opening. This setting lets you press the shutter and remove your hand completely from the camera before the shutter opens.

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Aug 15, 2021 11:22:48   #
CO
 
CHG_CANON wrote:
So normally, I say hold BBF with your thump and press the shutter at the same time. That is 'normally' one is not shooting in the near dark nor from a tripod. When you can work from a stable tripod platform, especially for a static subject like the abbey or your post-it tests, just focus and release the BBF. The subject is not moving, nor the camera; the focus remains where set. Then, just release the shutter.

The 2 second delay is the time between pressing the shutter and the shutter actually opening. This setting lets you press the shutter and remove your hand completely from the camera before the shutter opens.
So normally, I say hold BBF with your thump and pr... (show quote)


Good advice. I've noticed that even if my camera is on a tripod, my pressing the shutter button (even being very careful) can cause some camera shake. A 2 delay or using a remote shutter release fixes that problem.

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Aug 15, 2021 12:32:08   #
Dan' de Bourgogne
 
CHG_CANON wrote:
CO gave an excellent analysis and impact of your exposure parameters and how they negatively impacted your results. You asked about AF, an additional tip is to find something of 'contrast' in your image. Take the first vertical image in your selection. There's a candle on a shelf in the details of the arch. Using a single AF point selectively set on that candle and / or where the arch meets the sky gives your camera something of high contrast to assist the AF.

I don't want to come down 'hard on you', but I do want to correct the premise of your post. These examples are not the equipment's failure. These are entirely the photographer shooing in Manual exposure. The colors of this vertical view are nice, but the image fails in the soft focus. At 8 second, f/11, ISO-100, we see opportunities for a sharper image. If you raised the ISO by 4-stops to ISO-1600, you could increase the shutterspeed to 1/20 sec, a speed you probably could handhold for a sharp(er) image at 16mm (8 sec to 1/20 sec). You also could open the aperture wider by 2-stops to f/5.6 while adjusting your ISO to ISO-800 for the total 4-stop increase in light to the sensor.

If the VR on this lens let you handhold this almost sharp vertical at 8-seconds (!!), you could leverage that knowledge to not have to get to 1/20 sec. Maybe stay slower at 1/10 sec and not bring the ISO as high or open the aperture as much.
CO gave an excellent analysis and impact of your e... (show quote)


1) So...I appreciate here at HHG to learn things which are not made obvious in the common books or forums.
For instance, I dont remember to have read or heard that the "AF" does better work on contrasty area than on not contrasty zones...Interesting...now I will take care of that! Good tip anyway ...and quite easy to apply each time!

2) You wrote:
"At 8 second, f/11, ISO-100, we see opportunities for a sharper image. If you raised the ISO by 4-stops to ISO-1600, you could increase the shutterspeed to 1/20 sec, a speed you probably ..."

I notice You certainly made a "tip failure"...from ISO 100 to 1600 = 4 stops;
but from 8" to 1/20"= more than 7 stops...
You certainly intended to write 1/2 " (0.5 sec)...
OK...it's not a breaker...I understand the idea...
But I'm not sure to be able to take sharp picture handheld at 1/2 sec. (I never tried!)

I promise You to try it (1/2 sec) and to show You what will come out.
I know You have a great experience: so I believe Y're right and put much hope in handheld results.
BTW, this vertical picture was shot on tripod...with VR "ON"...Is'nt it the problem?

3) You wrote
"You also could open the aperture wider by 2-stops to f/5.6 while adjusting your ISO to ISO-800 for the total 4-stop increase in light to the sensor."

Yes...this is absolut correct...f/5.6 instead of 11 = 2 stops...SIO 800 instead of 100 is again 2 stops more...totzl increase is then 4 stops... I agree!
Discussing about this "vertical" picture...let's say its exposure is quite OK...(i feel it correctly balanced...not to dark...not to light)
But the thing You could not be aware of is: the camera is already on tripod+shutter delay set 2 sec=no risk for camera shake giving blurry image.
So, having said this...I choose ISO for noiseless image...f/11 for great DOF...and 8 sec because it gave a quite correct exposure.
Now my last question is: why do You recommend to give the sensor 4 stops more light? (I like to understand why I make what). i will follow all Your suggestions as long I know why.
Thank CHD CANON for all the help You already provided

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Aug 15, 2021 12:55:03   #
Dan' de Bourgogne
 
CHG_CANON wrote:
So normally, I say hold BBF with your thump and press the shutter at the same time. That is 'normally' one is not shooting in the near dark nor from a tripod. When you can work from a stable tripod platform, especially for a static subject like the abbey or your post-it tests, just focus and release the BBF. The subject is not moving, nor the camera; the focus remains where set. Then, just release the shutter.

The 2 second delay is the time between pressing the shutter and the shutter actually opening. This setting lets you press the shutter and remove your hand completely from the camera before the shutter opens.
So normally, I say hold BBF with your thump and pr... (show quote)


I see...message received 5/5!! From now..will be done like this!!! Thanks again 1000x

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