Auto ISO question

F

fiVe

Senior Member
​As I've said before, I have graduated to the D610 from a Canon T1i crop body, and I realize there is much to learn about this new Nikon. I have a question about the D610's auto ISO setting. I have done several test shots in my kitchen/breakfast nook. This is a open area that is lit on the nook side by incandescent lights and on the kitchen side by a big flourescent light--so it is mixed lighting. The camera almost always selects ISO 6400 for these test pics and they are over-exposed. Am I missing something obvious here?

On the Shooting Menu, the ISO sensitivity settings are:
ISO sensitivity 100
Auto ISO sensitivity control ON
Maximum sensitivity 6400
Minimum shutter speed AUTO

I realize I could force the ISO to a lower setting, but I'm curious about why the camera would select 6400 when the lighting, while not studio quality, is by no means low. I realize it's not an accurate comparison, but the T1i will shoot the pics at 1600.

Two other questions--
When shooting at 300mm with the above lighting, the ISO is always 6400.
When reviewing the pics, ISO is many times displayed in red (vs. white). What does a red ISO denote?

Thanks for your help. I realize I'm on a photography journey which takes time, but I want to learn all I can.

R/fiVe
 
G

gqtuazon

Gear Head
fiVe said:
​
On the Shooting Menu, the ISO sensitivity settings are:
ISO sensitivity 100
Auto ISO sensitivity control ON
Maximum sensitivity 6400
Minimum shutter speed AUTO

I realize I could force the ISO to a lower setting, but I'm curious about why the camera would select 6400 when the lighting, while not studio quality, is by no means low. I realize it's not an accurate comparison, but the T1i will shoot the pics at 1600.
Click to expand...

Using Matrix metering, the camera is trying to provide you a good and properly exposed image. Are you using a flash? If you are using a flash, you can limit the max ISO sensitivity to ISO 800 for example and let the flash compensate for the appropriate level of flash as long as you are using Through The Lens (TTL). This will keep the noise to your desired level.

fiVe said:
​
Two other questions--
When shooting at 300mm with the above lighting, the ISO is always 6400.
When reviewing the pics, ISO is many times displayed in red (vs. white). What does a red ISO denote?

Thanks for your help. I realize I'm on a photography journey which takes time, but I want to learn all I can.

R/fiVe
Click to expand...

The Red ISO reading indicates that the camera used a higher ISO level since you've programmed it to use ISO 100 as your minimum ISO sensitivity. IF you go outside while the sun is out, you will notice once you start shooting in a well lit environment, the camera will use the minimum ISO which is ISO 100 in this case. I hope that helps.

Welcome to the forum. :)
 
BackdoorArts

BackdoorArts

Senior Member
I believe your issue may have to do with the Auto shutter speed and a longer lens. I just tried testing this with my D600 and it seems that if you are in Aperture Priority mode the ISO will be set so that the camera shoots with a shutter speed faster than your focal length. In other words, as I zoomed in an out at a constant aperture the ISO changed with the shutter speed in a way that maintained a shutter speed faster than the current focal length.

So, if you've got a 300mm lens on the camera will set the ISO so that a shutter speed faster than 1/300s can be used.

When using Auto ISO I always set the minimum speed manually based on the lens I am using.
 
F

fiVe

Senior Member
BackdoorHippie said:
...as I zoomed in an out at a constant aperture the ISO changed with the shutter speed in a way that maintained a shutter speed faster than the current focal length....
Click to expand...

A very enlightening response. Thank you.

I checked the test pics and found that approx. half fit this shutter-speed-to-focal-length scenario. I assume the others are different because of the way the camera metered the shot. (E.g. ISO 6400, 300mm, shutter 1/60). I also reviewed the shots I considered overexposed and realized I had a composure faux pas. <head smack> The breakfast nook light was in the frame just over my wife's shoulder which (at iso 6400) caused that corner of the pic to be blown out. It also affected the rest of the photo (a bit too light), but the focus was razor sharp.

Full-frame with high ISO capability is a new world for me. I don't intend to make it harder than it is and look forward to long-term D610 education.

As always, I welcome any and all comments/instruction.

Merry CHRISTmas,
fiVe
 
Last edited:
BackdoorArts

BackdoorArts

Senior Member
fiVe said:
A very enlightening response. Thank you.

I checked the test pics and found that approx. half fit this shutter-speed-to-focal-length scenario. I assume the others are different because of the way the camera metered the shot. (E.g. ISO 6400, 300mm, shutter 1/60). I also reviewed the shots I considered overexposed and realized I had a composure faux pas. <head smack> The breakfast nook light was in the frame just over my wife's shoulder which (at iso 6400) caused that corner of the pic to be blown out. It also affected the rest of the photo (a bit too light), but the focus was razor sharp.

Full-frame with high ISO capability is a new world for me. I don't intend to make it harder than it is and look forward to long-term D610 education.

As always, I welcome any and all comments/instruction.

Merry CHRISTmas,
fiVe
Click to expand...

Once you hit ISO 6400 the camera has nowhere else to go, which is why the shutter speed stayed below the focal length - ISO could not go any higher in the natural range.

As was mentioned previously, switch to matrix metering if you're not using that already and it should save some of those blow-out moments when you've metered elsewhere.
 
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