Convert settings to another model (Canon PowerShot S120 -> G7X Mark II) - convert ISO to f stop?

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neveredit
neveredit New Member • Posts: 21
Convert settings to another model (Canon PowerShot S120 -> G7X Mark II) - convert ISO to f stop?

Hello, on my PowerShot S120 I had my favorite settings for a certain situation saved on C, the settings were:

Manual Mode - 1/200 - f 7.1 - ISO 80

I now have the G7X Mark II but this camera's lowest ISO is 125 (@canon: please bring back ISO 80 in future models), so I tranferred the settings to:

Manual Mode - 1/200 - f 7.1 - ISO 125

I realize that from ISO 80 to ISO 125, there is an increase of brightness by 56% -

here are my questions:

1. so to get the same effect, do I need to increase shutter speed by 56% (like 1/320), or increase f stop by 56% (like f 11), or 26% for each value?

2. Or can I achieve the same effect by exposure compensation?

Question with this is, a) is that possible in manual mode, and b) is this saved with the C settings, regardless of the position of the button on the camera?

3. Or Is there a way to convert ISO to f stops, like xx ISO equals yy f stops?

4. The other difference is of course that the S120 has 1.17" sensor size and the G7X has 1" sensor size, does that affect the above calculation, and if so, how?

Lots of question, I hope I can get some answers... Thank you!

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ANSWER:
Canon PowerShot G7 X Canon PowerShot S120
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tcg550 Veteran Member • Posts: 6,977
Re: Convert settings to another model (Canon PowerShot S120 -> G7X Mark II) - convert ISO to f stop?
2

On your original camera how did you come up with your favorite setting?

Use that same procedure on your new camera.

Klaus dk
Klaus dk Veteran Member • Posts: 5,202
Re: Convert settings to another model (Canon PowerShot S120 -> G7X Mark II) - convert ISO to f stop?
3

The difference between ISO 80 and ISO 125 is 2/3 of a stop, so you should get the same picture brightness if you use f/9 instead of f/7.1.

The difference in sensor size means that your DOF at f/9 on the G7XII is slightly more shallow than what you'd get at f/7.1 on the S120.

Since there's a SQRT(2) relation between two full f-numbers and a factor of two between two full stops of ISO, counting stops is more accurate and less confusing than calculating percentages.

I have no data on diffraction limits, but since the crop factor from 1" to 1"/1.7 is 1.7 (surprise!) the diffraction on the G7XII at f/9 must be less significant than on the S120 at f/7.1.

Good luck and good light.

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selected answer This post was selected as the answer by the original poster.
neveredit
OP neveredit New Member • Posts: 21
Re: Convert settings to another model (Canon PowerShot S120 -> G7X Mark II) - convert ISO to f stop?

Those settings were worked out in a workshop I attended, the teacher set my camera so that I could achieve a certain effect with those settings.

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Canon PowerShot S120 Canon G7 X II
Klaus dk
Klaus dk Veteran Member • Posts: 5,202
Re: Convert settings to another model (Canon PowerShot S120 -> G7X Mark II) - convert ISO to f stop?
6

neveredit wrote:

Those settings were worked out in a workshop I attended, the teacher set my camera so that I could achieve a certain effect with those settings.

Excuse me for saying so, but a teacher who does not teach you why, is not a teacher.

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Michael Fryd
Michael Fryd Veteran Member • Posts: 8,873
Re: Convert settings to another model (Canon PowerShot S120 -> G7X Mark II) - convert ISO to f stop?
3

neveredit wrote:

Hello, on my PowerShot S120 I had my favorite settings for a certain situation saved on C, the settings were:

Manual Mode - 1/200 - f 7.1 - ISO 80

I now have the G7X Mark II but this camera's lowest ISO is 125 (@canon: please bring back ISO 80 in future models), so I tranferred the settings to:

Manual Mode - 1/200 - f 7.1 - ISO 125

I realize that from ISO 80 to ISO 125, there is an increase of brightness by 56% -

here are my questions:

1. so to get the same effect, do I need to increase shutter speed by 56% (like 1/320), or increase f stop by 56% (like f 11), or 26% for each value?

2. Or can I achieve the same effect by exposure compensation?

Question with this is, a) is that possible in manual mode, and b) is this saved with the C settings, regardless of the position of the button on the camera?

3. Or Is there a way to convert ISO to f stops, like xx ISO equals yy f stops?

4. The other difference is of course that the S120 has 1.17" sensor size and the G7X has 1" sensor size, does that affect the above calculation, and if so, how?

Lots of question, I hope I can get some answers... Thank you!

You want to take the crop factor into account.

Convert your existing settings to the full frame "equivalent", and then to the crop factor of your new camera.

The PowerShot S120 has a crop factor of 4.6X

The G7X Mark II has a crop factor of 2.73X

Let's look at 1/200 - f 7.1 - ISO 80 on the PowerShot.   On a full frame you will get the same results at 1/200 - f/32 - ISO 1600  (multiply the f/stop by the crop factor, and the ISO by the square of the crop factor).

On the G7X that would 1/200 - f/12 - ISO 225. (divide the full frame f/stop by 2.73, and divide the ISO by 2.73 squared.

You can go directly from one to the other.  Multiply the f/stop by 1.7, and multiply the ISO by 2.8.

If you use these settings, then at the same angle of view, you should get the same depth of field.  You should also have the same shot noise, so as newer technology, the G7X should give a little bit better noise performance.

====

In terms of matching aperture to ISO.

When you change the aperture by a factor of 1.41 (square root of 2) you change the exposure by one stop (doubles or halves the light).    To alter the ISO by one stop you need to double or halve the value.

For instance f/2 at ISO 400 yields the same brightness as f/2.8 at ISO 800 (one stop smaller aperture, one stop higher ISO).

With shutter speeds, halving or doubling the shutter speed is a one stop change.

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tcg550 Veteran Member • Posts: 6,977
Re: Convert settings to another model (Canon PowerShot S120 -> G7X Mark II) - convert ISO to f stop?
1

neveredit wrote:

Those settings were worked out in a workshop I attended, the teacher set my camera so that I could achieve a certain effect with those settings.

Now's a good time to learn.

Set your new camera at your current settings. Take a photo, then adjust one of the 3 settings until you get the results you are looking for.

Then go back and start over changing one of the other settings until you get the results you want.

Note the relationship of the settings as you change them.

That's how you learn. You're fortunate to learn with digital because you have instant feedback. When a lot of us learned we had to wait for the film to get processed to see the results. I remember taking notes for each shot so I knew what was happening when I saw the results. Now you get exif data so it's easy to see what happens when you change one of the 3 variables.

mamallama
mamallama Forum Pro • Posts: 53,692
Re: Convert settings to another model (Canon PowerShot S120 -> G7X Mark II) - convert ISO to f stop?
2

neveredit wrote:

Hello, on my PowerShot S120 I had my favorite settings for a certain situation saved on C, the settings were:

Manual Mode - 1/200 - f 7.1 - ISO 80

I now have the G7X Mark II but this camera's lowest ISO is 125 (@canon: please bring back ISO 80 in future models), so I tranferred the settings to:

Manual Mode - 1/200 - f 7.1 - ISO 125

I realize that from ISO 80 to ISO 125, there is an increase of brightness by 56% -

here are my questions:

1. so to get the same effect, do I need to increase shutter speed by 56% (like 1/320), or increase f stop by 56% (like f 11), or 26% for each value?

2. Or can I achieve the same effect by exposure compensation?

Question with this is, a) is that possible in manual mode, and b) is this saved with the C settings, regardless of the position of the button on the camera?

3. Or Is there a way to convert ISO to f stops, like xx ISO equals yy f stops?

4. The other difference is of course that the S120 has 1.17" sensor size and the G7X has 1" sensor size, does that affect the above calculation, and if so, how?

Lots of question, I hope I can get some answers... Thank you!

Why do you need to calculate anything? Your camera is a versatile machine with a powerful computer. Use it.

Since you apparently like low ISO and 1/200 shutter speed. Set your camera to the lowest ISO of 125 and shutter speed to 1/200 and take a series of pictures in M Mode at various Aperture settings. Pick the one you like best and note the aperture and that is the setting you want.

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Klaus dk
Klaus dk Veteran Member • Posts: 5,202
A little deeper
1

One question for you: Why manual and why the settings 1/200 - f/7.1 - ISO 80?

neveredit wrote:

[...]

here are my questions:

1. so to get the same effect, do I need to increase shutter speed by 56% (like 1/320), or increase f stop by 56% (like f 11), or 26% for each value?

The difference between ISO 80 and ISO 125 is 2/3 of a stop.

2/3 stops faster than 1/200s is 1/320s. 2/3 stops smaller than f/7.1 is f/9, so at ISO 125 any of the combinations:
1/200s @ f/9
1/250s @ f/8
1/320s @ f/7.1
will give you the same picture brightness as 1/200s @ f/7.1 @ ISO 80.

However, when you increase sensor size and ISO, but keep shutter speed and f-stop (relative aperture) the same, brightness increases and DoF for the same field of view decreases.

If you bring the brightness down by using a faster shutter, you'll still have shallower DoF, and you may freeze movement that would previously result in blur.

If you want to keep DoF the same, you'll need to go to f/12 (roughly, because the ratio between sensor sizes are 1.7) and decrease shutter speed or increase ISO accordingly. At f/12, any of these combinations should give you the same picture brightness and DoF as the settings on the S120:
1/100s @ ISO 125
1/125s @ ISO 160
1/160s @ ISO 200
1/200s @ ISO 225

In other words: any change forces a new compromise.

2. Or can I achieve the same effect by exposure compensation?

No.

Question with this is, a) is that possible in manual mode

In manual mode, EC is irrelevant.

and b) is this saved with the C settings, regardless of the position of the button on the camera?

I don't know, but since EC is irrelevant, so is the question, IMHO.

3. Or Is there a way to convert ISO to f stops, like xx ISO equals yy f stops?

Yes. A doubling of ISO is one f-stop. Between two f-stops there's a factor of 1.4 or to be more precise: SQRT(2), so while ISO 400 is one stop faster than ISO 200, f/4 is two stops slower than f/2.

4. The other difference is of course that the S120 has 1.17" sensor size and the G7X has 1" sensor size, does that affect the above calculation, and if so, how?

Yes. I hope my calculations above demonstrates how.

Please note: I have assumed that you want to have the same field of view and that you have sufficient light to keep noise levels low. When it comes to ISO equivalence between sensors, I must admit my powers of understanding, calculation, and explanation are exhausted.

Lots of question, I hope I can get some answers... Thank you!

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neveredit
OP neveredit New Member • Posts: 21
Re: Convert settings to another model (Canon PowerShot S120 -> G7X Mark II) - convert ISO to f stop?

Hello Klaus,

thanks a lot, this really helps and is the sort of answer I was looking for 

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neveredit
OP neveredit New Member • Posts: 21
Re: Convert settings to another model (Canon PowerShot S120 -> G7X Mark II) - convert ISO to f stop?

Thank you, Michael, I will need to read this a few times to fully understand and remember.
Maybe I should've mentioned that these settings are used for flash where the background is underexposed, so to keep ISO as low as possible is necessary, this is why I wanted to change only shutter speed and/or aperture.

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neveredit
OP neveredit New Member • Posts: 21
Re: Convert settings to another model (Canon PowerShot S120 -> G7X Mark II) - convert ISO to f stop?

Thank you, that is a good idea. I just need to find a subject who is willing to let me take a close flash shot of them and keep still while I change the settings.
I attach a photo that I took on the S120 with those original settings.

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neveredit
OP neveredit New Member • Posts: 21
Re: A little deeper

Hello Klaus,

the settings are used for close ups with flash, I want the ISO as low as possible, so that the background is underexposed on purpose and only the subject is lit by the flash.
I attached a sample shot in another answer, but here is another one.
As for the rest, I need to print this out (old school, I know and read it a few times so I really understand, thank you!

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Michael Fryd
Michael Fryd Veteran Member • Posts: 8,873
Re: Convert settings to another model (Canon PowerShot S120 -> G7X Mark II) - convert ISO to f stop?
1

neveredit wrote:

Thank you, Michael, I will need to read this a few times to fully understand and remember.
Maybe I should've mentioned that these settings are used for flash where the background is underexposed, so to keep ISO as low as possible is necessary, this is why I wanted to change only shutter speed and/or aperture.

Then things may not work as you expect. You are assuming the flash metering of the two cameras are the same. The two cameras may also have different flash power.

A reasonable strategy is to take a few test photos without the flash. Try different settings until you are happy with the background (ignore your subject). Then you can turn on the flash and use Flash compensation to adjust the brightness of your subject.

I believe your new camera offers options not available with your old camera.

You can put your camera in one of the automatic modes.  Use regular exposure compensation to control the brightness of your background, and flash exposure compensation to control the brightness of your subject.

Some Cannon cameras allow you to lock or limit the shutter speed when using flash.  Check to see if that option is turned on.

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thebustos Veteran Member • Posts: 3,316
Re: A little deeper
2

neveredit wrote:

Hello Klaus,

the settings are used for close ups with flash, I want the ISO as low as possible, so that the background is underexposed on purpose and only the subject is lit by the flash.
I attached a sample shot in another answer, but here is another one.
As for the rest, I need to print this out (old school, I know and read it a few times so I really understand, thank you!

In your example, the background is part of the ambient exposure, which is controlled by the shutter speed. You could achieve similar results with a wider aperture and faster shutter speed than you are currently using, but there's more to it than that. Rather than clinging to these settings blindly I suggest you read up on the basics of flash photography to understand what is going on.

Your settings work for what you want to achieve, but they may be causing your flash to fire at a higher power than necessary, which in turn will cause your battery to drain faster.

-- hide signature --

Good luck and happy shooting!

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Michael Fryd
Michael Fryd Veteran Member • Posts: 8,873
Re: A little deeper

neveredit wrote:

Hello Klaus,

the settings are used for close ups with flash, I want the ISO as low as possible, so that the background is underexposed on purpose and only the subject is lit by the flash.
I attached a sample shot in another answer, but here is another one.
As for the rest, I need to print this out (old school, I know and read it a few times so I really understand, thank you!

Whether or not the background is dark is not directly related to ISO.  Simply use Exposure compensation to darken the background, and you can shoot in auto.

Use aperture priority, and select an aperture that gives you your desired depth of field.  Use Auto ISO and let the camera select the ISO and shutter speed.

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neveredit
OP neveredit New Member • Posts: 21
Re: A little deeper

I agree, I need to understand more of it all... 
As for the flash, in this custom setting, the flash is set at medium power. I can use min/med/max power and can choose between 1st/2nd curtain on the camera.
At night, I use an external slave flash because the camera doesn't have a hot shoe, with that I have more settings available.

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Michael Fryd
Michael Fryd Veteran Member • Posts: 8,873
Re: A little deeper
1

neveredit wrote:

I agree, I need to understand more of it all...
As for the flash, in this custom setting, the flash is set at medium power. I can use min/med/max power and can choose between 1st/2nd curtain on the camera.
At night, I use an external slave flash because the camera doesn't have a hot shoe, with that I have more settings available.

While an external flash may give you more settings, you lose the ability to have the camera automatically determine the correct flash exposure. You are limiting yourself to manual flash power.

Your camera isn't designed to be used with an external flash, so you may run into some strangeness when you try to use one. There may be issues with the external flash firing too soon, and your image comes out too dark.

This may not have been the best choice of camera if you want to use external flash. On the other hand, try it without the external flash. Put the camera into automatic mode, and adjust with exposure compensation, and flash compensation. See if you like the results.

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neveredit
OP neveredit New Member • Posts: 21
Re: A little deeper

I find that the inbuilt flash doesn't have enough power, this is why I bought the external flash. I only use it when it's dark, but I could also use it during the day because especially then, the inbuilt one doesn't reach very far.
Attached example of photo with external flash (different settings in the camera than in my original question of course)

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Michael Fryd
Michael Fryd Veteran Member • Posts: 8,873
Re: A little deeper
3

neveredit wrote:

I find that the inbuilt flash doesn't have enough power, this is why I bought the external flash. I only use it when it's dark, but I could also use it during the day because especially then, the inbuilt one doesn't reach very far.
Attached example of photo with external flash (different settings in the camera than in my original question of course)

Is this based on lessons learned from the old camera or have you tried the new camera in full auto?

The above image was taken at f/10.  That's going to require more flash power, and a longer exposure to keep the background from going completely black.  Was there a reason for shooting f/10 at 1/6 second?  At around f/4 and 1/60 second your back ground and foreground would be the same brightness using only 1/8 the flash power.

You want to make sure that you are not imposing the limitations of your old camera onto your new one.

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