Aperture priority combined with Auto ISO and Zoom lens seems odd

[pnodrog]

Nikon DSLRs and some of the newer Canon ones allow you to set both the aperture and speed when using manual mode with auto ISO enabled. It is a great way of keeping control of the shooting parameters you feel are most important. Using all the various modes you have the option of allowing the camera to do the required exposure adjustment using either the aperture, shutter speed, ISO or various combinations (or in Auto or P modes all) depending on your preference.

[ajax]

David, as hinted in Post #9, in your experiments with Aperture Priority Mode and Auto ISO, it might be helpful to you to include the effects of you changing the size of the aperture on your camera's chosen Auto ISO value. If your concern is depth of field you can investigate that by using the calculator here on CiC -
https://www.cambridgeincolour.com/tu...calculator.htm
For example, if you were photographing a bird 10 metres away from you with a 300mm focal length, increasing aperture size to f/11 (instead of f/22) would still give you about half a metre of depth of field, which should be sufficient, while the extra exposure at f/11 should cause your camera to reduce the ISO value to a level at which image noise is not a problem.

Philip

Thanks, this is new news for me. This discussion has made it apparent to me that there is more to it than simply wanting to crank up the aperture setting. Should be helpful input for the experiments I'm planning to do.

[Manfred M]

David - my usual work flow is the following:

1. Look at the lighting conditions and set the ISO that I think will work. In rare instances I will shoot using Auto-ISO mode;

2. Look at the scene that I am planning to shoot and decide on whether Depth of Field (DoF) or Motion (including freezing the subject) are the most important aspect of the scene I am planning to shoot. In most of the work that I do, I tend to concentrate on areas of the image where I want to maximize sharpness, so I shoot in Aperture Priority mode. Other times I will want the image to either freeze motion or accentuate motion. In those cases I will shoot using Shutter Priority mode. There are times I will shoot in 100% manual mode (manual selection of ISO, Shutter Speed and Aperture);

3. Select the aperture or shutter speed that I think will work for the image I am trying to make;

4. Focus and then frame my shot and take the picture; and

5. If it the first shot of the series, I will check my viewfinder to ensure everything is working out the way I want it to. I will check my histograms to ensure that the exposure is working and I will check what the shot looks like. I will use the magnification buttons on the back of the camera to zoom in to ensure that I am getting the effect I want.

If it is, I keep on shooting (without checking each image) and if it is not, I return to step 1 and go through the steps again.

For me, this is not a long process and I do all these things in a matter of seconds. It took a lot longer when I first started taking pictures.

[ajax]

Hopefully.

...

I would check and become familiar with your 'Auto ISO' function user settings if your camera has them.

Have now checked and it looks like my Canon EOS 1300D Camera does allow the maximum ISO to be adjusted down to 400 which would allow it to choose either 100, 200, or 400. This is good to know even if I don't yet quite know how to apply it. The need to do some experiments aimed at showing me the affect of changing ISO with my equipment has been a basic takeaway for me from this discussion.

[ajax]

...

Is there some good reason for you selecting f/22 - a very small aperture. Increasing the aperture should cause the camera to choose a lower ISO value, e.g f/11 should give ISO 200.

Philip

Actually I was not really trying to shoot with f22 so much as I was surprised by what the camera did. The way this came about is that those were the settings when I switched the camera from shutter to aperture priority. My recollection is a bit vague so I don't even remember if I ended up shooting anything but it did cause me to further investigate how the camera was operating with respect to aperture priority.

[ajax]

...
Edit - Additional Information Found

Delving further into this I have come across this article regarding Canon Auto ISO operation in Aperture Priority https://chrisbrayphotography.com/tips/auto_iso.php which is unclear of what Canon models it refers to but has Canon 'EOS 5D Mk11' written on a diagram. The explanation describes that ISO is determined by Focal Length in this configuration.

Very nice overview. Based on this as well as discussion herein it definitely appears as though cameras factor in focal length when determining shutter speed and ISO. While evidence did suggest this to be the case it came as surprise to me. Now I know better. Thanks.

[ajax]

David - my usual work flow is the following:
...

Thanks, it does happen that I understand the value of workflow (good procedures to follow) and for a novice like me this kind of lesson is very helpful.

[Stagecoach]

Nikon DSLRs and some of the newer Canon ones allow you to set both the aperture and speed when using manual mode with auto ISO enabled. It is a great way of keeping control of the shooting parameters you feel are most important. Using all the various modes you have the option of allowing the camera to do the required exposure adjustment using either the aperture, shutter speed, ISO or various combinations (or in Auto or P modes all) depending on your preference.

And the beauty of this is that you can very quickly 'alter' the three parameters by only having to rotate two thumb-wheels whilst still looking through the viewfinder on higher end camera models.

[DanK]

One thing that Canon cameras (at least up through the 5D III) don't let you do is add exposure compensation when using auto-ISO. That can be a substantial limitation.

Because increasing ISO degrades image quality, reducing dynamic range as well as introducing noise, I rarely want the camera to control it. I probably do 80% of my shooting either in full manual mode or in aperture priority with ISO fixed, and much of the rest is in shutter priority with ISO fixed. When I want a higher ISO--for example, to increase the impact of ambient light when using E-TTL flash--I set it manually. This is just what works for me, given what I shoot. There are situations, however, where auto-ISO is a life-saver. For example, I was asked to shoot a play that was under very uneven lighting. The lighting was quite dim, requiring high ISOs given that I couldn't use very slow shutter speeds, and I simply wasn't fast enough to figure out how much to change ISO when the lighting changed, so I used auto-ISO.

[xpatUSA]

One thing that Canon cameras (at least up through the 5D III) don't let you do is add exposure compensation when using auto-ISO. That can be a substantial limitation.

Because increasing ISO degrades image quality, reducing dynamic range as well as introducing noise, I rarely want the camera to control it. I probably do 80% of my shooting either in full manual mode or in aperture priority with ISO fixed, and much of the rest is in shutter priority with ISO fixed. When I want a higher ISO--for example, to increase the impact of ambient light when using E-TTL flash--I set it manually. This is just what works for me, given what I shoot. There are situations, however, where auto-ISO is a life-saver. For example, I was asked to shoot a play that was under very uneven lighting. The lighting was quite dim, requiring high ISOs given that I couldn't use very slow shutter speeds, and I simply wasn't fast enough to figure out how much to change ISO when the lighting changed, so I used auto-ISO.

Indeed, Dan, I see the bottom line of photography as the sensor exposure which is just comprised of aperture and shutter time. For me, the so-called "ISO" really has nothing to do with it. In my simple life, I still think that this whole ISO business is "largely irrelevant" designed only to make old-time film-shooters feel comfortable.

I wish I had $1000 for every time I've read that "ISO increases the sensor sensitivity" ...

[dje]

In post 15, I made the statement that the feature of automatic selection of minimum shutter speed based on lens focal length when using Auto ISO in A mode was not available on my Nikon D610. In fact, after further research, I have found that it is. In fact, it seems that it is probably available on all current Nikon DSLR's.

I wasn't aware of it as when you enter the minimum ss selection screen in the menu, the AUTO option is not visible and you have to scroll up past a long list of shutter speeds before you find it at the top. If you select this option, you then get a choice of standard mode which I believe selects the min ss based on the inverse of the focal length (FF equiv for crops I suspect). Alternatively you can vary this ss by 2 stops up or down.

So, you learn something new everyday. Thanks to OP David for raising the subject.

Dave

[Stagecoach]

In post 15, I made the statement that the feature of automatic selection of minimum shutter speed based on lens focal length when using Auto ISO in A mode was not available on my Nikon D610. In fact, after further research, I have found that it is. In fact, it seems that it is probably available on all current Nikon DSLR's.

I wasn't aware of it as when you enter the minimum ss selection screen in the menu, the AUTO option is not visible and you have to scroll up past a long list of shutter speeds before you find it at the top. If you select this option, you then get a choice of standard mode which I believe selects the min ss based on the inverse of the focal length (FF equiv for crops I suspect). Alternatively you can vary this ss by 2 stops up or down.

So, you learn something new everyday. Thanks to OP David for raising the subject.

Dave

And guess what ! It's also a selectable option in the 'minimum speed listing' on the D800 (not the D300) and works, but I never had a clue it was there

[DanK]

I wish I had $1000 for every time I've read that "ISO increases the sensor sensitivity" ...

I’d take $5. Still enough to fund a big purchase.



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