Why do you need high ISO ? (1 Viewer)

I must admit to having very limited experience of cameras, never having owned a DSLR ! but having checked back a year or two I find that the highest ISO shown on EXIF data has been 800, this in a gloomy woodland and at 40mtrs through undergrowth. Any darker and I would not have bothered to take a shot.

Used Nikon 8800, Nikon 900 and now the Nikon P1000 and almost every shot shows an exif of less than 400, taken in all normal lights ranging from overcast to brilliant sun, so why the need for high ISO ?

Den

Well, surely the other theoretical need for high ISO is in action shots? It would reduce blurring and get you a crisper movement rather than a smudge.

That being said, I myself (a user of a bridge camera) try to avoid going above 400 if I can, and certainly above 800 the graininess of it becomes offputting unless there is some very particular circumstance I want to try and capture.

Hi Den,

It is not completely clear what you're asking. Are you asking what the use for high ISO would be in the cameras you have used? Or are you asking why do bird photographers desire good image quality at high ISOs?

I think the answer to the first question is that there is not much use for high ISOs in super zoom cameras such as you are using, because the image quality deteriorates rapidly as the ISO rises. Cameras with larger sensors will have better image quality at high ISOs.

I think the answer to the second question is that if you have good image quality at high ISO, you will then be able to take photos in dark conditions where you are now not bothering to take a photo. Probably the most frequent situation in bird photography is photographing birds within a closed canopy forest. This problem becomes most acute in the tropics, where many of the most photogenic species only reside in such habitats.

For me its the need to stop action and the fact i now struggle holding the gear steady, high ISO gives me high shutter speeds.

My answer expounds on Jim's - I think the main point you make is that you don't bother to shoot in darker conditions and higher ISOs likely because you CAN'T get a nice, high-detail, low noise shot in those conditions. But what if you could? That's where I find a newer sensor with good high ISO ability to be useful - it lets me take shots at ISO 3,200, 6,400, even 12,800, in super-dark conditions or with requisite very high shutter speeds to freeze action and still get nicely exposed shots with good details.

Each time I've upgraded cameras, aside from improvements in focus systems, a big motivation has been improvements in high ISO performance that have allowed me to expand into photographing wildlife in situations I used to be unable to shoot. Similar to you, I would get to a point where the ISO got too high, the noise was too much, the detail was mostly gone, and I'd just have to write off that bird as too dark and hidden to shoot. With a good high-ISO capable sensor, where I used to stop shooting at ISO 800 I can now shoot at ISO 6,400, and get the same detail and noise levels that my older cameras used to put out at ISO 800.

It allows you to shoot where you once couldn't, and shoot action shots in poorer light than you used to. Of course, larger sensors usually mean significantly better high ISO capability. But even in the P&S lines, there have been some improvements with larger sensor cameras - comparing a 1/2.5" sensor to a 1/1.7" sensor to a 1" sensor, the improvements are very clear, and newer cameras often have better processing engines with better noise reduction algorithms that are less harmful to details...so even if you can't match the ISO levels of big-sensor DSLR and mirrorless interchangeable lens bodies, you can use an ISO 800 or 1600 and see better details and less intrusive noise with some of the newer bodies with newer processors and/or larger sensors.

I love high ISO capability simply for the peace of mind that I can raise it in order to set my aperture and shutter speed where I want them to be. Being at 1/4000th of a second lets me know im gonna freeze the action and if the camera can handle it having my ISO high up so I can support that shutter speed value.


-Matthew

Alexjh1 said:

I myself (a user of a bridge camera) try to avoid going above 400 if I can, and certainly above 800 the graininess of it becomes offputting

Click to expand...

I shoot with Shutter Priority to capture BiF on my bridge camera (SX60), so ISO is left on auto, but I have my preferences set to not let auto ISO go above 400 ISO for the reason above: the graininess is too distracting.

poledark said:

I must admit to having very limited experience of cameras, never having owned a DSLR ! but having checked back a year or two I find that the highest ISO shown on EXIF data has been 800, this in a gloomy woodland and at 40mtrs through undergrowth. Any darker and I would not have bothered to take a shot.

Used Nikon 8800, Nikon 900 and now the Nikon P1000 and almost every shot shows an exif of less than 400, taken in all normal lights ranging from overcast to brilliant sun, so why the need for high ISO ?

Den

Click to expand...

Here's some camera background. A camera sensor needs a certain number of photos to hit it to make an image. A camera has 3 things that affect that amount of light: shutter speed, aperture, and ISO setting. They are all related in the concept of a "stop" (from old days when turning a knob clicked between detent stops). Each stop is a doubling or halving of light, so you can trade them as you want -- make one larger or another smaller.

Shutter speed: the faster the less light. It is a linear relationship. 1/30th of a second lets in twice the light (i.e. "1 stop") as 1/60th. When using a long lens (where small shakes make big blur) or shooting faster moving things, you need faster shutter speeds.

Aperture: This relates to how big the opening is inside the lens. A lens has a minimum aperture (wide open) and can then "stop down" to close the opening. You stop down to get more in focus (bigger depth of field). Note that lower apertures are bigger openings because it is measured in f-stops, not mm of opening. Aperture is a sqrt(2) scale: 1, 1.4, 2, 2.8, 4, 5.6, 8, 11, etc. That is because it is a 2-dimensional opening so making the opening sqrt(2) bigger lets in twice the light. So f/2 to f/2.8 is 1 stop.

ISO: This is how sensitive the sensor is. You could think of it as how much amplification the sensor applies to the signal from the sensor. ISO 100 is usually the base ISO, some cameras will go down to ISO 64. The lower the ISO, the better quality image -- i.e. the less amplification and noise. The larger the ISO, the more effective light you have. So, ISO 200 is twice as sensitive as ISO 200. It is linear, so doubling is 1 stop.

Now you can trade off stops. You can double the ISO or half the shutter speed or reduce the aperture by sqrt(2) to increase the amount of light the camera "sees."

In your example, the Nikons used a low ISO because they had plenty of light. In the gloomy light, they had to bump up the ISO because there was not enough light. Cameras -- depending on the mode -- will use different equations to figure out the minimum desired shutter speed (due to lens size or subject motion) and aperture side (depending on subject profile), then cranks the ISO up or down to make the exposure workout. Cameras have their own little brains and algorithms to try and pick the right settings.

For birds, many people will use Shutter Priority so they can pick the speed they want, then the camera will auto adjust aperture and ISO. Many also use Manual mode so they set both the speed and aperture and only let the camera pick the ISO.

Marc

Many thanks to you all for the explanation. Coming from old school film cameras I do relate ISO to film grades and "graininess", push it to far and the pics are grainy/ noisy.

I have only used small sensor digital cameras so have never pushed the ISO up much above 8oo, never needed to to be honest, my p1000 will take useable pics right down to where I have difficulty seeing the subject with my eyes. Useable, not actually bright/sharp, and to be honest when it gets that dark I don't bother now.

Just recently I have ben using shutter priority and speeds of 1000 or 1200 and auto ISO, and today shot some pics in bright sun and strong winds to freeze the action at 1/1000sec, 2000mm, F6.3, and the camera picked ISO 360
.
A week before that I took some pics in pretty gloomy early evening slightly overcast, Shutter set at 1/1000 and the camera picked F5.6, ISO 1600 at 750mm. I am surprised the ISO didn't go higher, again, any darker and I wouldn't have bothered...…….


Den

poledark said:

Many thanks to you all for the explanation. Coming from old school film cameras I do relate ISO to film grades and "graininess", push it to far and the pics are grainy/ noisy.

I have only used small sensor digital cameras so have never pushed the ISO up much above 8oo, never needed to to be honest, my p1000 will take useable pics right down to where I have difficulty seeing the subject with my eyes. Useable, not actually bright/sharp, and to be honest when it gets that dark I don't bother now.

Just recently I have ben using shutter priority and speeds of 1000 or 1200 and auto ISO, and today shot some pics in bright sun and strong winds to freeze the action at 1/1000sec, 2000mm, F6.3, and the camera picked ISO 360
.
A week before that I took some pics in pretty gloomy early evening slightly overcast, Shutter set at 1/1000 and the camera picked F5.6, ISO 1600 at 750mm. I am surprised the ISO didn't go higher, again, any darker and I wouldn't have bothered...…….


Den

Click to expand...

The focal length actually does not matter much (apart from picking an appropriate minimum shutter speed). The aperture f-stop already factors in the focal length and size of aperture opening.

I like to think of this in terms of Exposure Value (EV) -- look at Table 1 and Table 2. If you had a light meter at the subject, you would find it has a certain level of illumination. In daylight, that is usually around an EV 15. Some light meters even measure in EV. Hasselblad used to mark their lenses in EV values.

1/1000 @ f/6.3 at ISO 100 would need about an EV 15.3 exposure (it's 1/3 stop over EV 15). So the camera would use maybe ISO 160. If the subject was darker, ISO 360 (EV 16.3) would make sense, or maybe the sunlight was more like EV 14.

Gloomy early evening might be more like an EV 11 illumination. 1/1000th at f/5.6 needs an EV 15 illumination, so you need to makeup maybe 4 stops. That would bring you up to ISO 1600.

Also, the smaller the sensor, usually the noiser higher ISOs are. The "grain" from film ISO roughly translates to digital as increased noise. Digital noise, however, is not a nice looking as film grain.

Marc

poledark said:

Many thanks to you all for the explanation. Coming from old school film cameras I do relate ISO to film grades and "graininess", push it to far and the pics are grainy/ noisy.

I have only used small sensor digital cameras so have never pushed the ISO up much above 8oo, never needed to to be honest, my p1000 will take useable pics right down to where I have difficulty seeing the subject with my eyes. Useable, not actually bright/sharp, and to be honest when it gets that dark I don't bother now.

Click to expand...

We've advanced way beyond the bad old days of film. Any current APS-C or Full-frame DSLR or mirrorless camera will yield perfectly acceptable pictures at ISO 3200 to 6400, and practically grainless at ISO 1600.