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#11
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Meaning of ISO value in digital photography?
On 06/14/2018 03:29 PM, Savageduck wrote:
On Jun 14, 2018, Jim-P wrote (in et): 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. Correct. The important thing is not to conflate analog ISO ratings with digital ratings. They are two different things. In a digital camera, presumably the sensor does not adjust itself to have greater sensitivity. Or does it? 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. The sensitivety does not change in the same way that analog film emulsions can be changed. Any increase from the base ISO is an increase of signal gain, or amplification of the signal from the sensor. So what is happening in a digital camera when I choose a greater ISO setting? Is more amplification being used? What you are doing when increasing the ISO number with a digital camera is increasing the signal gain between the sensor and the camera CPU. This is effectively the same as turning up the volume (gain) on an audio amplifier. As gain increases so does amplified noise. How the noise manifests itself depends on the sensor, the CPU, and the SNR of the pair. That is why some cameras have better high ISO performance than others. By using ISO to rate the base sensor sensitivity, and any increases by upping the gain just gives folks who have made the move from film to digital a rough guide by referencing film ISO. I tried to understand this page but it got far too technical.... https://photography.tutsplus.com/art...n--photo-11963 That article is spelling out the fact that digital ISO is not the equivalent of analoge ISO. That article does have a high nerd factor. Generally when an article emphasizes that we are using log-10 not log-e, you need a couple letters after your name! -- Ken Hart |
#12
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Meaning of ISO value in digital photography?
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 |
#13
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Meaning of ISO value in digital photography?
In article , Ken Hart
wrote: 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. 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. false. you're confusing 'grain', or digital noise, with resolution. a 3 kp camera has a lower *resolution* than a 48 mp camera. noise depends on the pixel size, or how much light is collected. larger pixels have less noise. sd is correct in that iso 200 on a digital camera is equivalent to iso 200 on a film camera with regards to exposure. it won't necessarily be *exactly* the same, but as he said 'close enough'. however, sd is not correct in that the grain/noise will be close. for digital, the noise will be *significantly* less than film grain at the same iso. it's nowhere near close. nikon d850 at iso 3200 & 25600: https://i.ytimg.com/vi/5k92LnEGOKo/maxresdefault.jpg nikon d810/d850/d500 at iso 12800: https://i.ytimg.com/vi/y_kk7QhS-MU/maxresdefault.jpg being able to shoot at iso 3200-6400 and beyond without worrying about noise opens up a whole new world not possible with film. |
#14
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Meaning of ISO value in digital photography?
In article , Ken Hart
wrote: In a digital camera, presumably the sensor does not adjust itself to have greater sensitivity. Or does it? Any given sensor will have a base sensitivety, or ISO. Typically ISO 200, or ISO 100 depending on manufacturer. Really? 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. actually, it isn't. I tried to understand this page but it got far too technical.... https://photography.tutsplus.com/art...ical-explorati on--photo-11963 That article is spelling out the fact that digital ISO is not the equivalent of analoge ISO. That article does have a high nerd factor. Generally when an article emphasizes that we are using log-10 not log-e, you need a couple letters after your name! the fact that the article is talking about p-n junctions and reverse biasing diodes indicates that its intended target audience are electrical engineers, not ordinary photographers. |
#15
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Meaning of ISO value in digital photography?
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. 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 |
#16
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Meaning of ISO value in digital photography?
On 6/14/2018 10:26 PM, Ken Hart wrote:
On 06/14/2018 03:29 PM, Savageduck wrote: On Jun 14, 2018, Jim-P wrote (in et): 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. Correct. The important thing is not to conflate analog ISO ratings with digital ratings. They are two different things. In a digital camera, presumably the sensor does not adjust itself to have greater sensitivity. Or does it? 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. The sensitivety does not change in the same way that analog film emulsions can be changed. Any increase from the base ISO is an increase of signal gain, or amplification of the signal from the sensor. So what is happening in a digital camera when I choose a greater ISO setting? Is more amplification being used? What you are doing when increasing the ISO number with a digital camera is increasing the signal gain between the sensor and the camera CPU. This is effectively the same as turning up the volume (gain) on an audio amplifier. As gain increases so does amplified noise. How the noise manifests itself depends on the sensor, the CPU, and the SNR of the pair. That is why some cameras have better high ISO performance than others. By using ISO to rate the base sensor sensitivity, and any increases by upping the gain just gives folks who have made the move from film to digital a rough guide by referencing film ISO. I tried to understand this page but it got far too technical.... https://photography.tutsplus.com/art...n--photo-11963 That article is spelling out the fact that digital ISO is not the equivalent of analoge ISO. That article does have a high nerd factor. Generally when an article emphasizes that we are using log-10 not log-e, you need a couple letters after your name! 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. -- PeterN |
#17
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Meaning of ISO value in digital photography?
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! |
#18
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Meaning of ISO value in digital photography?
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...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. 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. |
#19
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Meaning of ISO value in digital photography?
On Jun 15, 2018, John McWilliams wrote
(in article ): 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! I believe that there are going to be quite a number of exceptions. ;-) -- Regards, Savageduck |
#20
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Meaning of ISO value in digital photography?
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...echnical-explo 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...camera-same-am azing-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 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. True. However, that was in the days of 25 ASA film. Things have changed, along with high ISO performance with fast lenses, there are other technical improvements with things such as various types of image stabilization with stabilized lenses (VR, IS, OIS), and in camera image stabilization (IBIS). -- Regards, Savageduck |
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