auto ISO and noise

[GlynRDav]

I have been reading about this and there seems to be quite opposite views.
One suggests to expose to the right (over expose but using zebra/blinkies to not blow highlights). Another suggests to under expose and pull the shadows up in post.
I use auto ISO mainly because the light is varying (birds and animals) and change the exposure compensation to over or under expose.
What I have found, if I use say -.3 to -1 the ISO value is lower, which sort of indicates less noise. On the other hand, if I use +.3 to +1, the ISO value is higher, which indicates more noise.
The tests were using the same light conditions.
I am not sure if I understand this correctly and I would appreciate some help.
TIA
Glyn

 

[Brownie]

I have been reading about this and there seems to be quite opposite views.
One suggests to expose to the right (over expose but using zebra/blinkies to not blow highlights). Another suggests to under expose and pull the shadows up in post.
I use auto ISO mainly because the light is varying (birds and animals) and change the exposure compensation to over or under expose.
What I have found, if I use say -.3 to -1 the ISO value is lower, which sort of indicates less noise. On the other hand, if I use +.3 to +1, the ISO value is higher, which indicates more noise.
The tests were using the same light conditions.
I am not sure if I understand this correctly and I would appreciate some help.
TIA
Glyn

You can't go by numbers. One shot in ISO XXXX could look great, and another one not so great. It has much to do with the subject and composition. I took about 200 images Friday night in fairly low light, from ISO 1600 up to 12800. Some of the images @ ISO 4000 looked worse than some at ISO 8000.

I had the exposure compensation set up for 2/3 stop overexposed most of the day, although when it really got dark and shutter speed mattered, I rolled it back to 0.

Overexposing (or Expose To The Right, "ETTR") is a common trick. I don't think it's the best way to shoot Auto ISO in low light though, for some of the reasons you state. I would rather sort out the aperture and shutter and have ISO set where I'm comfortable. Then, if I want to ETTR I know how it will affect my settings.

One thing though, I have never heard anyone say to underexpose and pull up the shadows when specifically discussing noise. That's a fine method for not blowing out highlights, but not for noise. Maybe double check the context of the recommendations.

DSC00942 by Shotglass Photo, on Flickr

 

[GlynRDav]

Thanks Brownie, that has given me something to think about. BTW, what were the settings and ISO value for this image?

 

[Brownie]

Thanks Brownie, that has given me something to think about. BTW, what were the settings and ISO value for this image?

1/1600, f/1.8, ISO 5000.

Noise reduction was applied in Affinity, then the image was exported as a PNG and processed in Darktable. Not my chosen workflow, but for some reason Darktable still doesn't recognize Sony's Lossless Compressed RAW files, so I open them in Affinity first then do as stated. I'm going to stop shooting in Lossless though for now, too much of a hassle with so many to process.

 

[Brownie]

Here's another example. It had gotten pretty dark by this time. 1/800, F/1.4, and ISO 6400. The white main subject helped control noise. Same processing.

BTW, all of these dark shots were with an A74, and LA-EA5, and a Minolta Maxxum 85/1.4

DSC01107 by Shotglass Photo, on Flickr

 

[GlynRDav]

You must have had a lot of fun photoing these incredible cars

 

[Brownie]

You must have had a lot of fun photoing these incredible cars

It's a riot! Here's a link to my post from yesterday. You can click through any of these images to see my Flickr Page.

Milan Dragway Heads Up! 5/5/23

Explore this photo album by Shotglass Photo on Flickr!

flic.kr

 

[Deleted Member 5003]

Hi Gly,
As a general rule it is better to expose to the right, or more precisely to your image highlights,
so you don't blow them out, and/or get any blinkies, and then recover shadows in post as necessary.

Given the expanded dynamic range on modern cameras, unless you have a camera with a restricted
range on the low light side, recovery of shadows is much easier than blown our highlights...once your
highlights are blown, the highlight detail is truly gone.

Your metering setting will also affect the shadows and highlights dependant upon your image composition
- predominantly highlights, predominantly shadows or generally balanced/neutral.

Matrix metering is ok for a balanced image, whilst for high % of shadows or highlights matrix metering
can be tricky and may confuse the camera exposure algorithm and spot or central metering may be a better
metering option together with a degree of exposure compensation.

The settings of exposure compensation are counter intuitive to the degree of illumination/exposure or
darkening of the image, as you note, increased +EC darkens and increases noise whilst the reverse for
-EC.

Hope this helps with your original question.

 

[Deleted Member 5003]

Please read Glyn in my earlier post....apologies for the name typo Glyn.....

 

[GlynRDav]

Thank you Deleted Member 5003, no worry about my name- I have called worse things.
I have some work to do to understand how the exposure affects different situations and light. I will persevere.

 

[alexpler]

Hi Gly,
As a general rule it is better to expose to the right, or more precisely to your image highlights,
so you don't blow them out, and/or get any blinkies, and then recover shadows in post as necessary.

Given the expanded dynamic range on modern cameras, unless you have a camera with a restricted
range on the low light side, recovery of shadows is much easier than blown our highlights...once your
highlights are blown, the highlight detail is truly gone.

Your metering setting will also affect the shadows and highlights dependant upon your image composition
- predominantly highlights, predominantly shadows or generally balanced/neutral.

Matrix metering is ok for a balanced image, whilst for high % of shadows or highlights matrix metering
can be tricky and may confuse the camera exposure algorithm and spot or central metering may be a better
metering option together with a degree of exposure compensation.

The settings of exposure compensation are counter intuitive to the degree of illumination/exposure or
darkening of the image, as you note, increased +EC darkens and increases noise whilst the reverse for
-EC.

Hope this helps with your original question.

Is that so? I find the +EC enbrightens the picture, -EC darkens it and saves some difficult highlights. I usually use -EC when I like the ISO, aperture and shutter settings but still some highlights are marked with the zebra stripes.

On the other hand, I tend to expose to the left, as I prefer my images darker and then enhance the shadows if needed. But that's personal taste and a subjective decision. But I'm surprised to read that EC works the other way around as I thought

As for the auto ISO, I set minimum ISO to 100 and maximum ISO to 6400 and never have to worry about the noise, as Sony system's noise management is that good.

 

[Deleted Member 5003]

Is that so? I find the +EC enbrightens the picture, -EC darkens it and saves some difficult highlights. I usually use -EC when I like the ISO, aperture and shutter settings but still some highlights are marked with the zebra stripes.

On the other hand, I tend to expose to the left, as I prefer my images darker and then enhance the shadows if needed. But that's personal taste and a subjective decision. But I'm surprised to read that EC works the other way around as I thought

As for the auto ISO, I set minimum ISO to 100 and maximum ISO to 6400 and never have to worry about the noise, as Sony system's noise management is that good.

I think i didnt fully explain the counter intuitive nature of EC.......the point i was trying to make was more in relation to wholly bright and dark scenes. If you have a bright scene comprised of generally whites(highlights) your camera will tend to underexpose (as the algorithm is always trying to achieve a gray scale image) and hence +EC is often necessary on such bright scenes to achieve the correct exposure rather than -EC, and similarily with a dark scene heavy in shadows where to achieve the correct exposure -EC will be needed.

For balanced highlight/shadow scenes EC will generally work in the way you indicate.

 

[alexpler]

I think i didnt fully explain the counter intuitive nature of EC.......the point i was trying to make was more in relation to wholly bright and dark scenes. If you have a bright scene comprised of generally whites(highlights) your camera will tend to underexpose (as the algorithm is always trying to achieve a gray scale image) and hence +EC is often necessary on such bright scenes to achieve the correct exposure rather than -EC, and similarily with a dark scene heavy in shadows where to achieve the correct exposure -EC will be needed.

For balanced highlight/shadow scenes EC will generally work in the way you indicate.

Now I understand haha. Thank you. I guess haven't faced with that issue given that generally I don't tend to shoot wholly bright scenes...

 

[Deleted Member 5003]

Now I understand haha. Thank you. I guess haven't faced with that issue given that generally I don't tend to shoot wholly bright scenes...

Apologies for the confusion...i should have been more clear.

 

[Jeff A]

I'm a follower of Mark Galer. His rule, expose for the Highlights, process for the shadows. And for what it's worth, he considers the "Auto ISO, minimum shutter speed" one of the best settings for Sony.