On Jun 14, 2018, Ken Hart wrote
(in article ):
On 06/14/2018 08:05 PM, Savageduck wrote:
On Jun 14, 2018, Jim-P wrote
(in article ):
On Thu, 14 Jun 2018 14:26:40 -0400, PeterN wrote:
On 6/14/2018 1:48 PM, Jim-P wrote:
In film cameras, ISO referrs to the sensitivity to light of the emulsion.
Manufacturers formulate different film emulsions with different
sensitivites tarding increased grain with increased ISO speed.
In a digital camera, presumably the sensor does not adjust itself to have
greater sensitivity. Or does it?
So what is happening in a digital camera when I choose a greater ISO
setting? Is more amplification being used?
I tried to understand this page but it got far too technical....
https://photography.tutsplus.com/art...n--photo-11963
I am going to try to give you a simplified, non-technical explanation.
As with most generalities it is not 100% technically accurate, but
should serve as a guideline.
ISO is a measurement of the light sensitivity of the sensor. Digital ISO
is adjustable in many cameras. And yes, it is a matter of adjusting the
amplification. If you are using a wider lens opening, and slower shutter
speed, you will be able to use a lower ISO.
Digital noise is one of the undesired artifacts in the image. Higher ISO
will result in more digital noise, and lessor image quality. Many of the
newer high quality sensors are designed to work at a higher ISO, with
less noticeable noise, and reduction in image quality.
There are some of us here who do not object to noise, while others have
serious objections. The point at which noise becomes objectionable often
comes down to a matter of taste and personal preferences.
Thanks. This makes me wonder what ISO I should set, if I don't leave it on
auto.
In the film days, we used the "Sunny-16" rule: Set the shutter speed
equal to the ISO (then "ASA"). In bright sunshine, use f/16. Slightly
cloudy- use f/11, open shade- f/8, full shade- f/5.6. This technique
would usually give a good exposure.
Combine that with the "focal length equals shutter speed" rule: The
longer the focal length, the faster the shutter speed to give acceptable
hand-held images. For a 200mm lens, you use a shutter speed of 1/250
second.
Example: 100mm lens calls for 1/100 second minimum. Set the ISO also at
100, and use the "Sunny-16" rule. Then refer to SD's exposure triangle,
three paragraphs down...
Let us start by asking, what camera are you using?
It would still be good to know what camera the OP is using.
As far as which ISO you should use you should consider the light environment
of the scene you are trying to capture, along with your interpretation of
that scene, all balanced to achieve an acceptable exposure.
Auto ISO can work, but you are going to be better off if you have an
understanding of the exposure triangle and photography in general. It might
be time for you to read a book on photography.
f/stop, shutter speed, and ISO.
That is where we all should start.
With a higher ISO, you can use a faster shutter speed and smaller lens
aperture. You get better motion stopping and depth of field, but you
also get grain (or noise).
With a lower ISO, you need to either use a slower shutter speed or a
wider aperture. You get better "grain", but you lose motion-stopping or
depth of field.
It's all a trade-off.
That is the story in a nutshell.
Does ISO 200 on a digital camera broadly match the grain/noise of ISO 200
Fujicolor or Kodacolor that I used to use years ago?
Close enough.
I'm going to have to respectfully disagree with SD here, but just on his
two word paragraph.
Well, I guess my two word paragraph was an over simplification for a
photographer new to digital photography. My “close enough” should have
been qualified as relative to the camera being used, and we have yet to
assertain what the OP is using. In my case I am using APS-C Nikon, and
Fujifilm cameras.
The "grain" of a digital sensor would be relative to the pixel count of
that sensor. To go to the extreme, a 3K-pixel toy camera would have a
"grainy" image no matter how low you dial the ISO- assuming that such a
camera would have that feature! OTOH, a 48M-pixel medium format digital
back would have a very tight "grain" pattern, exceeding that of 35mm ISO
200 film.
What the digital sensor produces is noise, and to call it “grain” is
wishful thinking. At higher digital ISO settings, or increased gain noise
becomes more apparant. The amount of noise depends on the sensor (size, and
vintage) and CPU camera manufacturer. These days it is not necessary to go to
a large MF format sensor to exceed the performance of 35mm ISO 200 film.
There are APS-C cameras such as the D500, X-T2, and X-H1which can do that
without much effort.
However, there are some software emulations which are capable producing very
good emulations of analog film grain which appear to be grain, not noise. Two
of the best at doing this are NIK Silver Efex Pro2, and Alien Skin Exposure
X3. Then Fujifilm has very good in-camera film emulations which produce
excellent results with three levels of simulated film like grain production.
Or do the ISO settings for a digital camera give quite different results to
the ISO values of film?
In a digital camera the ISO settings are going to be a close approximation
of ISO values of film, and are more guidelines rather than exact figures.
In fact, there will _some_ variation in the ISO between manufacturers of
film, and the emulsion batches. Which is why many pros would buy large
quantities of film, and shoot a few test rolls before shooting work for
pay.
....and some of those pros still have rolls of film in refrigerated storage.
For example, you are going to find it difficult to dig up ISO 51200 film, but
there are digital cameras capable of producing acceptable images with ISO
that high.
--
Regards,
Savageduck