FingerPainter
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Nice camera, but not a lens I'd use for indoor photos without flash.
This is a long post. There is a summary at the end.
The problem you are seeing in these photos, the grainyness and softness, is the visible effect of noise. Noise is variation in signal from expected value. In photography, "expected" generally means the average value of surrounding pixels. When a pixel differs it stands out as brighter, darker or having a different hue.
Noise in photos comes from two sources. The camera adds some noise, but in your photos almost all the noise was variation present in the light itself even before it was captured by the camera. This variation in light is random and originates due to the quantum nature of the emission of light from its source.
The way you overcome the negative visual effects of variation in light is to collect more light in the photo. The more light you collect, the more the random variations in the light average out to something closer to the expected value.
The amount of light collected by the camera in a photo depends on three things:
All of these approaches are subject to constraints, however. Often the photographer is unable or not permitted to add light to the scene. Too wide an aperture might result in too shallow a Depth of Field (DoF) or too much blur from aberrations, and lenses have limits to their max aperture. Too slow a shutter may result in blur from subject movement or camera movement.
Lets look at your two images and see what you might have done to reduce the noise in them.
The first one is shot at 170mm, 1/100 f/6.3 ISO 2500 with -1 EC. The rule of thumb for shutter speed fast enough to avoid camera motion blur is to shoot at least as fast as 1/(focal length x crop factor). At 170mm that means you should be shooting at no slower than 1/255. However you have a VR lens so you should be able to get at least two stops slower, say 1/60 and still avoid camera motion blur. If you catch the trombonist when the slide is not moving, then 1/60 should adequately freeze subject motion. Your aperture was set to f/6.3. You don't need the extra DoF this gives instead of f/5.6, The young woman behind the trombone's bell doesn't need to be sharply focused. So you could have captured one stop more light if you had shot at 1/60 f/5.6. My inadequate EXIF reader tells me you were in S mode, but not whether you had Auto-ISO set. I suspect you didn't, or if you did that you had set max ISO to 2500. Why would the camera set the aperture to f/6.3 if it was fee to set a higher ISO? For shots like these use auto ISO and set a higher limit. Doing so might have prevented the camera from narrowing aperture to f/6.3. IDK why you had EC of -1. There are no highlights that need protecting, and if anything the scene is lighter than average and thus would need a positive EC, if any. You are shooting in RAW. this is good if you know how to develop and you use the right profiles. You have greater control over shadow and highlight processing, white balance, brightness adjustment, sharpening and noise reduction. Light levels are too low to worry about ETTR. All RAW files need some sharpening and many need noise reduction.
The second photo was taken at 150mm, 1/320 f/5.6 ISO6400, again with -1 EC. Violinist's bows are almost always moving so the shutter speed may well be appropriate, and that faster shutter is the main reason for the extra noise in this image. If you think you can catch her when the bow is momentarily still, try 1/60 again, and get 2 and 1/3 stops more exposure, dropping ISO back down to 2500. The aperture is at max. Nothing you can do there. Use Auto-ISO and lose the -1 EC.
So with your current equipment, you might have improved the first photo's noise by one stop. That's not a lot. If you can catch the violinist motionless, you might get a bit over 2 stops improvement. That's better, but catching a violinist motionless isn't easy, so maybe there was no improvement to be had. To get better noise performance than this you need a faster lens of the correct focal range, or a camera with a larger or more efficient sensor. Neither is an inexpensive solution.
A 70-200mm f/2.8 VR lens would offer you two stops more light and cover the focal lengths you are using, while continuing to allow you to shoot stationary subjects at about 1/60. This will double your Signal to Noise Ratio. That's often a noticeable improvement in noise. You'd need a monopod or tripod with this lens. A monopod works best in confined space or when you need to adjust shooting position.
Somebody suggested that you use an 85mm f/1.8G lens and crop to get the same framing, That might be less of a solution than it first seems. f/1.8 is 3 and 1/3 stops faster than f/5.6, but when you crop you are throwing away light. The cropped image will be noisier than the uncropped original. To get the same framing with an 85mm from the same distance, you will have to crop to 1/4 of the original. That throws away 2 stops of the 3 1/3 stop advantage. You are also throwing away 3/4 of the pixels, so the image will not be as sharp. The 85mm f/1.8G is sharper than your 18-200mm, but it's linear resolution isn't anywhere near twice as high, so you'd be taking a noticeable sharpness penalty to get the 4/3 stop noise improvement. IMO, if you display large enough to see the noise problems, the loss of resolution will be even more visible than the noise improvement. The 85mm f/1.8 G doesn't have VR so you'd have to increase your slowest shutter from 1/60 to 1/160. ( 1/(85 * 1.5) = 1/127.5. There is no such shutter speed and the slowest speed faster than this is 1/160.) 1/160 is 4/3 stops faster than 1/60, so when subject motion allows you to shoot at 1/60 but lens stabilization doesn't, you have no net gain in noise performance with the 85mm.
One other lens you could look for is the Sigma 50-150mm f/1.8. It is discontinued so you'd have to buy used. It's specs are right (or close enough - you may have to crop a little bit, but the faster aperture makes up for it in this case) but IDK how well it performs in terms of sharpness and autofocus. Your 18-200 isn't l that sharp at 150-200mm, so the Sigma is unlikely to be significantly worse, and may be better. I'd expect the Sigma'S AF to be slow though, because 150mm f/1.8 requires large elements. That may be why Sigma replaced it in their lineup with a 50-100mm f/1.8. Elements would mass less than half as much. The 50-100 though would suffer from similar problems as the 85mm for this application.
Don't bother looking for a different APS-C camera to get higher efficiency. Efficiency differences between contemporary cameras of the same format are usually not more than about 1/3 stop, and the D500 is one of the more efficient APS-C models. If you want to see a noise improvement from a different camera, you'd need to switch to FX. A D750 currently costs a bit less than your D500, which is about the same price as a 70-200mm f/2.8 VR II. It will give about 1.1 stops better noise performance. A D610 will cost a few hundred dollars less, and give the same noise performance but its AF and metering won't be as good. However, if you move to FX you will need longer focal lengths to get the same framing. If you are currently shooting in a range from 135mm to 200mm on DX you'd need 200-300m on FX You won't find an f/2.8 zoom covering that range, only f/4 or slower so there is no gain to be had by getting an FX camera to shoot at these subject distances.
The 70-20mm f/2.8 VR II lens will give you a bigger improvement for about the same cost as a different body. You can consider an older or used model or a lens from a third party, as long as it has some form of optical image stabilization
Summary
This is a long post. There is a summary at the end.
The problem you are seeing in these photos, the grainyness and softness, is the visible effect of noise. Noise is variation in signal from expected value. In photography, "expected" generally means the average value of surrounding pixels. When a pixel differs it stands out as brighter, darker or having a different hue.
Noise in photos comes from two sources. The camera adds some noise, but in your photos almost all the noise was variation present in the light itself even before it was captured by the camera. This variation in light is random and originates due to the quantum nature of the emission of light from its source.
The way you overcome the negative visual effects of variation in light is to collect more light in the photo. The more light you collect, the more the random variations in the light average out to something closer to the expected value.
The amount of light collected by the camera in a photo depends on three things:
- The amount of light falling on the sensor, per unit area
- The surface area of the sensor from which the image is made, and
- The efficiency of the sensor in converting light falling on it into an electrical charge.
- The amount of light in the scene (scene luminance)
- The T-stop the lens is set at (F-stop is a close approximation and the factor we can actually control)
- The length of time the sensor is exposed to light (shutter speed)
- Get as much light in the scene as possible, by using flash, lamps, reflectors, opening window shades and doors...
- Use as wide an aperture as possible.
- Use as slow a shutter as possible,
All of these approaches are subject to constraints, however. Often the photographer is unable or not permitted to add light to the scene. Too wide an aperture might result in too shallow a Depth of Field (DoF) or too much blur from aberrations, and lenses have limits to their max aperture. Too slow a shutter may result in blur from subject movement or camera movement.
Lets look at your two images and see what you might have done to reduce the noise in them.
The first one is shot at 170mm, 1/100 f/6.3 ISO 2500 with -1 EC. The rule of thumb for shutter speed fast enough to avoid camera motion blur is to shoot at least as fast as 1/(focal length x crop factor). At 170mm that means you should be shooting at no slower than 1/255. However you have a VR lens so you should be able to get at least two stops slower, say 1/60 and still avoid camera motion blur. If you catch the trombonist when the slide is not moving, then 1/60 should adequately freeze subject motion. Your aperture was set to f/6.3. You don't need the extra DoF this gives instead of f/5.6, The young woman behind the trombone's bell doesn't need to be sharply focused. So you could have captured one stop more light if you had shot at 1/60 f/5.6. My inadequate EXIF reader tells me you were in S mode, but not whether you had Auto-ISO set. I suspect you didn't, or if you did that you had set max ISO to 2500. Why would the camera set the aperture to f/6.3 if it was fee to set a higher ISO? For shots like these use auto ISO and set a higher limit. Doing so might have prevented the camera from narrowing aperture to f/6.3. IDK why you had EC of -1. There are no highlights that need protecting, and if anything the scene is lighter than average and thus would need a positive EC, if any. You are shooting in RAW. this is good if you know how to develop and you use the right profiles. You have greater control over shadow and highlight processing, white balance, brightness adjustment, sharpening and noise reduction. Light levels are too low to worry about ETTR. All RAW files need some sharpening and many need noise reduction.
The second photo was taken at 150mm, 1/320 f/5.6 ISO6400, again with -1 EC. Violinist's bows are almost always moving so the shutter speed may well be appropriate, and that faster shutter is the main reason for the extra noise in this image. If you think you can catch her when the bow is momentarily still, try 1/60 again, and get 2 and 1/3 stops more exposure, dropping ISO back down to 2500. The aperture is at max. Nothing you can do there. Use Auto-ISO and lose the -1 EC.
So with your current equipment, you might have improved the first photo's noise by one stop. That's not a lot. If you can catch the violinist motionless, you might get a bit over 2 stops improvement. That's better, but catching a violinist motionless isn't easy, so maybe there was no improvement to be had. To get better noise performance than this you need a faster lens of the correct focal range, or a camera with a larger or more efficient sensor. Neither is an inexpensive solution.
A 70-200mm f/2.8 VR lens would offer you two stops more light and cover the focal lengths you are using, while continuing to allow you to shoot stationary subjects at about 1/60. This will double your Signal to Noise Ratio. That's often a noticeable improvement in noise. You'd need a monopod or tripod with this lens. A monopod works best in confined space or when you need to adjust shooting position.
Somebody suggested that you use an 85mm f/1.8G lens and crop to get the same framing, That might be less of a solution than it first seems. f/1.8 is 3 and 1/3 stops faster than f/5.6, but when you crop you are throwing away light. The cropped image will be noisier than the uncropped original. To get the same framing with an 85mm from the same distance, you will have to crop to 1/4 of the original. That throws away 2 stops of the 3 1/3 stop advantage. You are also throwing away 3/4 of the pixels, so the image will not be as sharp. The 85mm f/1.8G is sharper than your 18-200mm, but it's linear resolution isn't anywhere near twice as high, so you'd be taking a noticeable sharpness penalty to get the 4/3 stop noise improvement. IMO, if you display large enough to see the noise problems, the loss of resolution will be even more visible than the noise improvement. The 85mm f/1.8 G doesn't have VR so you'd have to increase your slowest shutter from 1/60 to 1/160. ( 1/(85 * 1.5) = 1/127.5. There is no such shutter speed and the slowest speed faster than this is 1/160.) 1/160 is 4/3 stops faster than 1/60, so when subject motion allows you to shoot at 1/60 but lens stabilization doesn't, you have no net gain in noise performance with the 85mm.
One other lens you could look for is the Sigma 50-150mm f/1.8. It is discontinued so you'd have to buy used. It's specs are right (or close enough - you may have to crop a little bit, but the faster aperture makes up for it in this case) but IDK how well it performs in terms of sharpness and autofocus. Your 18-200 isn't l that sharp at 150-200mm, so the Sigma is unlikely to be significantly worse, and may be better. I'd expect the Sigma'S AF to be slow though, because 150mm f/1.8 requires large elements. That may be why Sigma replaced it in their lineup with a 50-100mm f/1.8. Elements would mass less than half as much. The 50-100 though would suffer from similar problems as the 85mm for this application.
Don't bother looking for a different APS-C camera to get higher efficiency. Efficiency differences between contemporary cameras of the same format are usually not more than about 1/3 stop, and the D500 is one of the more efficient APS-C models. If you want to see a noise improvement from a different camera, you'd need to switch to FX. A D750 currently costs a bit less than your D500, which is about the same price as a 70-200mm f/2.8 VR II. It will give about 1.1 stops better noise performance. A D610 will cost a few hundred dollars less, and give the same noise performance but its AF and metering won't be as good. However, if you move to FX you will need longer focal lengths to get the same framing. If you are currently shooting in a range from 135mm to 200mm on DX you'd need 200-300m on FX You won't find an f/2.8 zoom covering that range, only f/4 or slower so there is no gain to be had by getting an FX camera to shoot at these subject distances.
The 70-20mm f/2.8 VR II lens will give you a bigger improvement for about the same cost as a different body. You can consider an older or used model or a lens from a third party, as long as it has some form of optical image stabilization
Summary
- Use RAW if you know how, and apply sharpening and noise reduction judiciously. Otherwise shoot JPEG.
- Set ISO to 100 then set Auto-ISO with a high upper limit.
- Shoot in S mode unless you find the camera not giving you max aperture (then shoot in M and set aperture to max.)
- Use VR.
- Set Shutter to 1/60 when you can catch the subject not moving. Adjust to faster otherwise, to freeze subject motion, but never use a faster shutter than you need to.
- Set EC to 0.
- Get a faster lens that covers 135mm - 200mm. For this application a 70-200mm f/2.8 with VR/VC/OIS is best, with a monopod.
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