Mystery of OIS & 1/50 Solved

[Stuart Richardson]

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I have also noticed different levels of sharpness in certain areas of the images when I use cameras or lenses with stabilization. I assumed that with a 5 axis stabilization, the sensor itself is moving with pitch, yaw and roll. If there are slight inaccuracies in the system, I would imagine that the lens and sensor could be less than ideally plane parallel. That is what I had thought might be responsible for this behavior (for example, one side being slightly sharper than another in a lens you otherwise know to be perfectly centered). But maybe something else is going on?

[SrMi]

2 hours ago, Stuart Richardson said:

I have also noticed different levels of sharpness in certain areas of the images when I use cameras or lenses with stabilization. I assumed that with a 5 axis stabilization, the sensor itself is moving with pitch, yaw and roll.

The sensor can only move in the X and Y directions and can rotate.

[David Wien]

I was taking photos in a museum with subdued lighting today. OIS was turned off and I used aperture priority. In the menus, shutter speed limit and ISO were set to auto and maximum ISO was set to 6400.

I found that the minimum shutter speed that the Q3 wanted to use was 1/50 sec: it would compensate by raising ISO until it reached ISO 6400 at which point it would sometimes set a lower speed. (If I set f/8, it would respond with 1/15s.) I have never had this obstinate phenomenon with my Canon cameras. Maybe there is another menu setting that causes this, but I havent found it. My point is that the 1/50 phenomenon discussed in this thread is independent of the IOS setting.

David

[ksrhee]

The exposure setting is determined by the combination of aperture, shutter speed, and ISO. If you are in aperture priority, the system will try to keep the ISO as low as possible while setting the shutter speed. If the shutter speed cannot be minimum, the ISO setting will be raised to bring up the shutter speed to a minimum.   If it doesn't need to raise the ISO setting, then it will pick the ideal shutter speed at the ISO to meet the exposure requirement.  Of course, things change if you are in the shutter priority or complete manual mode, in which case, you can adjust all three to achieve the ideal exposure setting you want - you have complete control of all three settings.  

[adrianh]

David, please check your Auto ISO Min shutter setting . I am sure it’s set to 1/50 😉 

[SrMi]

2 hours ago, David Wien said:

I was taking photos in a museum with subdued lighting today. OIS was turned off and I used aperture priority. In the menus, shutter speed limit and ISO were set to auto and maximum ISO was set to 6400.

I found that the minimum shutter speed that the Q3 wanted to use was 1/50 sec: it would compensate by raising ISO until it reached ISO 6400 at which point it would sometimes set a lower speed. (If I set f/8, it would respond with 1/15s.) I have never had this obstinate phenomenon with my Canon cameras. Maybe there is another menu setting that causes this, but I havent found it. My point is that the 1/50 phenomenon discussed in this thread is independent of the IOS setting.

David

Increase the max ISO if you do not want your camera to lower the shutter speed when hitting ISO 6400.

The only reason to use a lower max ISO is to limit the maximum noise (though noise can vary at the same ISO). To "guarantee" that noise limit, the camera needs to lower the shutter speed; otherwise, the noise will increase.

[David Wien]

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8 hours ago, adrianh said:

David, please check your Auto ISO Min shutter setting . I am sure it’s set to 1/50 😉 

Under Auto ISO settings, Shutter Speed Limit is set to Auto, Is there another setting that I am unaware of?

It may just be that this behaviour is radically different from what I have become used to with my Canon R6.

But my point is that it is the same whether IOS is active or not.

David

Edited March 9, 2024 by David Wien

[Guest]

Auto shutter speed at 28mm defaults to a minimum of 1/50s which is the nearest to 1/(2f).

If you apply the digital crop you'll see that the minimum shutter speed increases accordingly. At 90mm it is 1/160s which, again, is nearest to 1/(2f)

 

[David Wien]

3 hours ago, Corius said:

Auto shutter speed at 28mm defaults to a minimum of 1/50s which is the nearest to 1/(2f).

If you apply the digital crop you'll see that the minimum shutter speed increases accordingly. At 90mm it is 1/160s which, again, is nearest to 1/(2f)

 

Thanks! I wondered about that. (It has no scientific basis with high resolution sensors!)  I never use the digital in camera crop, but your experiment confirms the formula.

David

[ksrhee]

6 hours ago, Corius said:

Auto shutter speed at 28mm defaults to a minimum of 1/50s which is the nearest to 1/(2f).

If you apply the digital crop you'll see that the minimum shutter speed increases accordingly. At 90mm it is 1/160s which, again, is nearest to 1/(2f)

 

Yes, the rule of thumb for shutter speed is twice the focal length.  If the algorithm within the Q3 uses that, then it is what it is.  Some cameras give you the options  (typically Auto1 and Auto2) so that you can go lower than the rule of thumb.  

[David Wien]

Well, firstly, this rule of thumb is based on film practice and is no guarantee of lack of blurred images today; and secondly, it seems to me that most cameras dont impose the rule of thumb at all.

David

[ksrhee]

This has nothing to do with film or digital . . .  to get a sharp focus, you need to increase the shutter speed with the longer lenses.  With IBIS or OIS, you can lower the shutter speed, and it will compensate.   Why bother with Auto when you can set the minimum shutter speed manually?  

[David Wien]

It is not about focus, but about ability to hold the lens stationary, and the limit of movement before it is noticeable on the recorded image. (Circle of confusion stuff.)

David

[ksrhee]

Yes, I know.  I wasn't referring to the focal point but rather the visual acuity.  However, I guarantee your picture will be out of focus if the camera shakes.

[adan]

Terminology difference.

In English, photographic "focus" refers strictly to the sharpness acheived by correctly setting distance and sharpness with the focus ring or other mechanism (bellows, AF, etc.).

It is not an interchangeable synonym for "sharp" or "accute."

A perfectly-focused picture can be sharp.

OR it can be blurry, due to camera shake, subject movement, a "soft-focus" filter, or even just a crummy lens, or alens with a fingerprint on the glass.

But such blur is not a "focus" problem. It is a shake/movement or optical problem.

[adrianh]

On 3/9/2024 at 8:36 AM, David Wien said:

Under Auto ISO settings, Shutter Speed Limit is set to Auto, Is there another setting that I am unaware of? It may just be that this behaviour is radically different from what I have become used to with my Canon R6. But my point is that it is the same whether IOS is active or not.

David

Sure, but you can just change it to whatever you would like to have. I use for people 1/125 and for landscape way slower (1/15 or even 1/8). The Auto Setting is maybe here not clearly described, in other cameras you have some options like F, 2F, 3F (which means of course 1/F(ocal Lenght) and so on). I am not familiar with Canon's way, but Sony has an Auto, Auto Faster, Auto Fastest and so on which is also a standard deviation of the 1/F rule of thumb.

Edited March 10, 2024 by adrianh

[David Wien]

25 minutes ago, adrianh said:

Sure, but you can just change it to whatever you would like to have. I use for people 1/125 and for landscape way slower (1/15 or even 1/8). The Auto Setting is maybe here not clearly described, in other cameras you have some options like F, 2F, 3F (which means of course 1/F(ocal Lenght) and so on). I am not familiar with Canon's way, but Sony has an Auto, Auto Faster, Auto Fastest and so on which is also a standard deviation of the 1/F rule of thumb.

I must admit my ignorance: I am not aware of such a setting, either in Canon or Q3.  Can you tell me on which page it comes in the Q3 manual, please?

David

[Guest]

1 hour ago, David Wien said:

I must admit my ignorance: I am not aware of such a setting, either in Canon or Q3.  Can you tell me on which page it comes in the Q3 manual, please?

David

Page 103/104 of the manual. Specifically "Limiting Shutter Speed Ranges" is at the top of page 104.

As I mentioned above "Auto" seems to be 1/(2F) but that isn't explicitly mentioned.

[David Wien]

28 minutes ago, Corius said:

Page 103/104 of the manual. Specifically "Limiting Shutter Speed Ranges" is at the top of page 104.

As I mentioned above "Auto" seems to be 1/(2F) but that isn't explicitly mentioned.

Many thanks for this: I shall re-read it forthwith!

David

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[David Wien]

OK. Thanks Corius. My problem was in understanding the meaning of the term "max shutter speed" which I find ambiguous, and I interpreted it wrongly. I would have expressed this as longest shutter time. The shutter stays open longer when set to 1/50 than 1/1000, which I would equate to slower, and for me the term "max shutter speed is the fastest one!

I just downloaded the German user manua, whichl has this for the relevant paragraph:

Es kann ein maximaler ISO-Wert eingestellt werden, um den Bereich der automatischen Einstellung einzugrenzen ( Maximaler ISO-Wert ). Zusätzlich kann auch eine maximale Belichtungszeit eingestellt werden.

This is crystal clear. I should have consulted the German Bedienungsanleitung earlier; but, since German is my fifth language and by no means as strong as my English, it is a bit of a chore to read!

Thanks again!

David