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Meaning of ISO value in digital photography?



 
 
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  #31  
Old June 16th 18, 09:58 PM posted to rec.photo.digital
Ken Hart[_4_]
external usenet poster
 
Posts: 384
Default Meaning of ISO value in digital photography?

On 06/15/2018 07:11 PM, Carlos E.R. wrote:
On 2018-06-15 22:18, Jim-P wrote:
On Thu, 14 Jun 2018 19:47:36 -0700, Savageduck wrote:

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 ):



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.


I am using a smartphone camera. Although it is not as high quality as a
DSLR the principles should be the same and I am interested in understanding
them before taking my photography further.

The smartphone model is a Moto G5 Plus with a Sony IMX362 Exmor RS camera
module which is also used in the Nokia 7 and Samsung S7 Edge

https://phoneproscons.com/794/moto-g...enfone-3-zoom/

I recall that old Sunny 16 rule and the thing which strikes me most about
it now is how slow the shutter speeds were in the old days. 1/250 was one
of the faster speeds I would use for day to day photography years ago but
my current smartphone often uses speeds of 1/1000 or 1/2000 which is
fantastic because by hand steadiness is not what it used to be.


My old SLR had 1/2000

The mechanics had a trick that allowed high effective shutter speed
while the shutter in fact moved relatively slowly, at 1/60 or
thereabouts. And old trick, actually. It opened a slit on the rectangle,
and the slit travelled the length of the aperture. If the slit was 1/5,
the effective speed was the actual speed multiplied by 5.

That is the standard way a focal plane shutter works (worked) for speeds
typically over 1/60 second. The first curtain would start to open, and
before it was all the way open the second curtain would start to close.
To use electronic flash, you could not sync at a speed where the shutter
was not totally open. Vertical travel focal plane shutters usually
sync'ed at a faster speed because they had less distance to travel.

The shutter tester I use to test my cameras provides a readout of the
shutter speed and each curtain speed. Typically, for my Canon FX
cameras, the curtain speed is in the neighborhood of 12msec. If there a
difference in the speeds of the two curtains, one side of the frame will
be over- or under-exposed.

When you photograph a subject moving across the frame (such as a fast
car), the subject will be either compacted or stretched in length,
depending on direction of travel.

--
Ken Hart

  #32  
Old June 16th 18, 10:13 PM posted to rec.photo.digital
Alan Browne[_2_]
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Posts: 64
Default Meaning of ISO value in digital photography?

On 2018-06-16 16:58, Ken Hart wrote:

That is the standard way a focal plane shutter works (worked) for speeds
typically over 1/60 second. The first curtain would start to open, and
before it was all the way open the second curtain would start to close.
To use electronic flash, you could not sync at a speed where the shutter
was not totally open. Vertical travel focal plane shutters usually
sync'ed at a faster speed because they had less distance to travel.


It was around 1/200s by around 1990 or so for a lot of SLR's, my Maxxum
9 went to 1/300 for sync; 7D to 1/250; a900 to 1/250 or 1/300 (don't
recall offhand).

1/60 is quite old as far as sync speeds go ...

--
"2/3 of Donald Trump's wives were immigrants. Proof that we
need immigrants to do jobs that most Americans wouldn't do."
- unknown protester
  #33  
Old June 16th 18, 11:32 PM posted to rec.photo.digital
Ken Hart[_4_]
external usenet poster
 
Posts: 384
Default Meaning of ISO value in digital photography?

On 06/16/2018 05:13 PM, Alan Browne wrote:
On 2018-06-16 16:58, Ken Hart wrote:

That is the standard way a focal plane shutter works (worked) for
speeds typically over 1/60 second. The first curtain would start to
open, and before it was all the way open the second curtain would
start to close. To use electronic flash, you could not sync at a speed
where the shutter was not totally open. Vertical travel focal plane
shutters usually sync'ed at a faster speed because they had less
distance to travel.


It was around 1/200s by around 1990 or so for a lot of SLR's, my Maxxum
9 went to 1/300 for sync; 7D to 1/250; a900 to 1/250 or 1/300 (don't
recall offhand).

1/60 is quite old as far as sync speeds go ...

My cameras are 1964-69 vintage, so "quite old" is fairly accurate!

The Maxxum 9 was a vertical shutter. The shutter has less distance to
travel vertically (24mm opposed to 36mm for horizontal), so it would
have a faster sync speed. The reviews I found for that camera put it in
the late 1990's.

--
Ken Hart

  #34  
Old June 17th 18, 03:22 AM posted to rec.photo.digital
PeterN[_7_]
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Posts: 946
Default Meaning of ISO value in digital photography?

On 6/14/2018 11:10 PM, Savageduck wrote:
On Jun 14, 2018, Ken Hart wrote
(in article ):

On 06/14/2018 03:29 PM, Savageduck wrote:


Snip

Any given sensor will have a base sensitivety, or ISO. Typically ISO 200, or
ISO 100 depending on manufacturer.


Really? I've never looked into that, but I would have thought that the
base sensitivity would be closer to the mid-point of the camera's ISO
setting range. But that's just electronics design practice.


Yup!

Take the Nikon D800 which has a base of ISO 100, and the D810 which has been
reduced to ISO 64. Any increase in ISO is an increase of signal gain from the
sensor. Both of those cameras are capable of dealing with very high ISO
settings without producing noticeable noise.

In the APS-C world the D500 has a base of ISO 100, and can be cranked up to
ISO 51,200, and extended to an unthinkable ISO 1,640,000.


So they say. However, I have found the noise on my D500 at 51,000, to be
significant. However the noise at a higher ISO will also increase with
higher contrast lighting conditions.




My APS-C Fujifilm X-T2 on the other hand can shoot from a base ISO 200 to ISO
12800, and can be extended down to ISO 160, 125, & 100, or up to ISO 25,600,
and ISO 51,200.

These are worth a read:

https://www.bhphotovideo.com/explora...aphy/tips-and-
solutions/understanding-exposure-part-4-iso

https://www.jmpeltier.com/2018/02/13/what-is-extended-iso-native-iso/

This one is a real simplification:

https://photographylife.com/what-is-iso-in-photography



--
PeterN
  #35  
Old June 17th 18, 03:54 AM posted to rec.photo.digital
PeterN[_7_]
external usenet poster
 
Posts: 946
Default Meaning of ISO value in digital photography?

On 6/15/2018 3:00 PM, John McWilliams wrote:
On 6/14/18** PDT 9:16 PM, PeterN wrote:
On 6/14/2018 10:26 PM, Ken Hart wrote:


Both you and the Duck are correct. It all boils down to what type of
image the photographer is looking to make. I use auto ISO when I want
to use a fixed shutter speed, and a fixed aperture. As for setting an
upper limit, there are times when a really noisy image is preferable
to no image at all. I would very much prefer a very noisy and grainy
image of the abominable snow man, to no image at all.


I've set my Canons to ISO 200 and keep it there* as I want the feedback
from aperture or shutter speed telling me when I am on the edge of
insufficient light.

* There are some exceptions!


Most of us have different photographic interests. I use auto ISO
primarily for high speed sync, and some landscape. i consider auto ISO
only as another tool which I use mostly to get a desired effect. some
use auto ISO for panos.When it comes to photo art, i think that the
image maker should use tools that he is comfortable using. And if he has
the interest, see if an alternative method would produce a result closer
to the result the maker seeks. Several weeks ago I started working on an
image about 9:30 AM. I just couldn't get quite the look I wanted. I kept
trying different tools. I finally got a bit hungry, and walked away from
the computer. It was after 11:00 PM.

--
PeterN
  #36  
Old June 17th 18, 04:09 AM posted to rec.photo.digital
PeterN[_7_]
external usenet poster
 
Posts: 946
Default Meaning of ISO value in digital photography?

On 6/15/2018 7:49 PM, Jim-P wrote:


snip



I wonder what the cost is for a point and shoot giving pictures a notch
above a smartphone.


If you like smart phone photography, by all means you should continue
with it. There are some photo artists who do a lot of good work with
smart phones. This year NECCC is having a lot of time devoted to the
smart phone. Tony Sweet, also is a smart phone enthusiast, as well as
being a highly talented artist and a good person..
https://www.slickpic.com/blog/interview-tony-sweet/
I have not specifically answered your question, because there is no
answer. Some smart phones can be expensive,n while some P&S cameras can
be very cheap, or priced higher than a smart phone.
It's whatever you prefer working with.

--
PeterN
  #37  
Old June 17th 18, 04:11 AM posted to rec.photo.digital
Savageduck[_3_]
external usenet poster
 
Posts: 15,307
Default Meaning of ISO value in digital photography?

On Jun 16, 2018, PeterN wrote
(in article ):

On 6/14/2018 11:10 PM, Savageduck wrote:
On Jun 14, 2018, Ken Hart wrote
(in article ):

On 06/14/2018 03:29 PM, Savageduck wrote:


Snip

Any given sensor will have a base sensitivety, or ISO. Typically ISO 200,
or ISO 100 depending on manufacturer.

Really? I've never looked into that, but I would have thought that the
base sensitivity would be closer to the mid-point of the camera's ISO
setting range. But that's just electronics design practice.


Yup!

Take the Nikon D800 which has a base of ISO 100, and the D810 which has been
reduced to ISO 64. Any increase in ISO is an increase of signal gain from
the sensor. Both of those cameras are capable of dealing with very high ISO
settings without producing noticeable noise.

In the APS-C world the D500 has a base of ISO 100, and can be cranked up to
ISO 51,200, and extended to an unthinkable ISO 1,640,000.


So they say. However, I have found the noise on my D500 at 51,000, to be
significant. However the noise at a higher ISO will also increase with
higher contrast lighting conditions.


Here is my X-T2 maxed out at an extended ISO 51,200. At 100% the noise is
obvious, but in general it is possible to capture an interpretable image even
at that high ISO. That D500 ISO 1,640,000 would be an impossible mess on the
X-T2.

This is an SOOC JPG, out of the X-T2 @ ISO 51,200, XF16mm f/1.4 @ f/4, 1/58
second, no PP NR applied.

https://photos.smugmug.com/photos/i-9xMDs8m/0/5814404e/O/i-9xMDs8m.jpg



My APS-C Fujifilm X-T2 on the other hand can shoot from a base ISO 200 to
ISO 12800, and can be extended down to ISO 160, 125, & 100, or up to ISO
25,600, and ISO 51,200.

These are worth a read:

https://www.bhphotovideo.com/explora...aphy/tips-and-
solutions/understanding-exposure-part-4-iso

https://www.jmpeltier.com/2018/02/13/what-is-extended-iso-native-iso/

This one is a real simplification:

https://photographylife.com/what-is-iso-in-photography


--

Regards,
Savageduck

  #38  
Old June 17th 18, 06:44 PM posted to rec.photo.digital
Jim-P
external usenet poster
 
Posts: 7
Default Meaning of ISO value in digital photography?

On Fri, 15 Jun 2018 17:34:57 -0700, Savageduck wrote:

On Jun 15, 2018, Jim-P wrote
(in article ):

On Fri, 15 Jun 2018 13:46:46 -0700, Savageduck wrote:

On Jun 15, 2018, Jim-P wrote
(in article ):

On Thu, 14 Jun 2018 19:47:36 -0700, Savageduck wrote:

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...-technical-exp
lo
ration--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.

I am using a smartphone camera. Although it is not as high quality as a
DSLR the principles should be the same and I am interested in understanding
them before taking my photography further.

The smartphone model is a Moto G5 Plus with a Sony IMX362 Exmor RS camera
module which is also used in the Nokia 7 and Samsung S7 Edge

https://phoneproscons.com/794/moto-g...y-imx362-rear-
camera-same-amazing-sensor-as-in-xplay-6-and-zenfone-3-zoom/

There is nothing wrong in using a smartphone camera. However, you are going
to have limitations which you will not find in modern DSLR, or mirrorless
digital cameras (MILC). Even with third party photo apps for your smartphone
you are going to have limitations of physical sensor size, and adjustability
of the exposure triangle.

The next question is; are you intending to add a modern digital camera to
your current photography kit?


I need to work out how to get the best from my smartphone first.

I'm new to smartphones but they take surprisingly good pictures which are
almost as good as my point and shoot. They are aso very forgiving and
don't need lots of setting up.


If it meets your needs there is little point looking for something else, but
if you want more you should consider something other than a compact/P&S
camera.

I wonder what the cost is for a point and shoot giving pictures a notch
above a smartphone.


There are some excellent compact, or P&S cameras from most of the
manufacturers such as Canon, Nikon, Panasonic, Sony, etc, prices, and
performance vary. The big issue with the P&S cameras is, they are being
killed off by smartphones. The big advantage to a dedicated camera rather
than a phone camera is ergonomics. No matter how much one might argue, a
smartphone is awkward to use as a camera due to its unavoidable phone shape.

Personally, if one is only considering a compact/P&S camera as an upgrade
from a smartphone, consider what you are going to be doing with your
photography, it might be better to stick with the smartphone. Otherwise, I
would suggest moving to a mirrorless camera with, or without interchangeable
lenses. They can be more expensive than a smartphone, but your photographic
experience will be more enjoyable.

I an unabashed fan of the Fujifilm mirrorless cameras, and for somebody
wanting something reminiscent of the analog days, a great fixed focal length
camera is the Fujifilm X100F.

https://www.dpreview.com/reviews/fujifilm-x100f
https://www.techradar.com/reviews/fujifilm-x100f-review

I currently own several Fujifilm bodies and a bag full of lenses.

https://www.dropbox.com/s/5yeyllbh2jd8g0a/IMG_2527e.jpg

To get some idea of what is out there in the compact camera range check out
dpreview:

https://www.dpreview.com


That's some serious looking gear in the camera bag!

The Fuji X100F camera is a fancier than I was considering. I was thinking
of something more along the lines of a Panasonic Lumix DMC-TZ70 but not for
some time yet.
 




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