re-occurring grainy pics PLEASE HELP!

[MichelleP]

I have a re-occurring problem and I am hoping someone here can help me figure it out. A lot of my pictures seem grainy when my focal distance is longer than about 10 feet. I have a Nikon D90 and mostly use my 50mm f1.8 lens. Although I had the same problem with my kit lens which is 17-105 ( I think). This is even outside. I usually keep my ISO between 200-400. I did some tests using a tripod and timer shots at different distances. These are test shots for grain only so they are not great shots These test shots are in AP mode. The first one is nice and clear at 3 feet f/2.8, 1/1250sec, ISO 400

Next is the pic at 12 ft. f5.6, 1/400, ISO 400 ( I will zoom in and post a grainy snip next)

and zoomed in at 100%

Any ideas?

 

[KmH]

Avoid dappled sunlight.
Use open shade instead and make sure you nail the exposure so your subject is not under exposed.
In open shade use a reflector(s) or flash(s) to light your subject.

Digital photos do not have grain, they have image noise and there are several different kinds of image noise.
All digital photos made with a DSLR have some amount of image noise.
Under exposure makes image noise more visible and image noise is first seen in the darker parts of a digital photo because the darker portions of the photo have less image data.
Digital Camera Image Noise: Concept and Types
http://www.adobe.com/digitalimag/pdfs/linear_gamma.pdf
Optimizing Exposure
ETTR
Exposing to the right - Wikipedia, the free encyclopedia

Tones & Contrast

• Understanding Histograms, Part 1: Tones & Contrast
• Understanding Histograms, Part 2: Luminosity & Color

 

[MichelleP]

This is very helpful thank you! I will dig more into those articles tomorrow. I contacted Nikon and they said my 50mm lens works best at 2-12 feet. Is it true that image noise can be worse at a longer focal distance? Or it seems from what you said mine is probably more from being underexposed?

 

[Kawaracer]

Is the 'D-lighting' active? With my D90 I had the impression that the when is was on I had more noise even in bright conditions and low ISO

 

[Overread]

Focal length won't affect noise - noise is a property of the sensor and the exposure.


However if you're using a longer focal length lens a few things can happen;

1) Resolution of detail might not be as crisp as at shorter focal lengths - this is especially the case with many zoom lenses where the longer focal lengths can be a touch softer than the short. Note that this will vary lens to lens, some (many 70-200mm variations) are very sharp and the drop is minimal - others (50-500mm or 18-200mm) can have a more noticeable drop, encouraging you to stop down by one stop of aperture when at the long end (no lens is sharpest at its maximum aperture - stopping down by one stop can thus improve sharpness performance - although again it varies lens by lens - higher end options can be very sharp even wide open).

2) Handshake - when you're using a longer focal length lens the impact of your bodies shake is increased. Typically the rule of thumb is 1/focal length of lens for the minimum shutter speed possible without getting handshake.

This is only a rough value and assumes that you're using a good holding and standing posture coupled with low fatigue. As you get more tired or hold the camera poorly or even might have more sway in your body than others you might find a need to use faster speeds. It's quite individual so try out different values and see what works for you.

3) If using a long telephoto lens heat-haze and atmospheric haze can become elements to consider. This tends to be a null issue until you're into 500mm or longer lenses.


If you want to test your lens for its image quality you can set it on a tripod and then aim at a static subject at a 45 degree angle (this ensures that you will not have handshake nor subject motion as blurring elements - and also that your depth of field will land on the subject). Then just vary the aperture, ISO, distance and focal lengths and have a play around. Sure they'll all be dull, boring shots but it might help you better come to understand the working performance of your camera and lens.

 

[The_Traveler]

You aren't posting a 100% crop for people to see; you are taking a screen shot of the picture at 100%.
It is much more useful if you actually do the following.
Zoom the image to 100%, then, using the crop tool, crop down to a piece that fits completely on the screen with nothing hidden- in this case, just crop away everything but her face.
Then post that image directly by using the upload a file option seen next to the Post Reply box.

 

[Designer]

This is very helpful thank you! I will dig more into those articles tomorrow. I contacted Nikon and they said my 50mm lens works best at 2-12 feet. Is it true that image noise can be worse at a longer focal distance? Or it seems from what you said mine is probably more from being underexposed?

I think the reason you see more noise at a longer range is because the camera's light meter is "averaging" the light, and the bright areas in the background are somewhat over exposed while your subject's face (being in the shade) is underexposed. You can use spot metering to meter for the face and you'll get a better exposure (of her face) even though the bright areas in the background will probably be even more overexposed.

So meter correctly for the subject, and watch your overall light quality (avoid dappled light).

 

[The_Traveler]

The reason there is noise in the shadows is pretty simple (at least my understanding is simple)

There is always some electronic noise originating from the sensor no matter where.
Where the strong light signal falls on the sensor the signal to noise ratio is great and you can't see the noise because the actual signal overwhelms it.
If there is low light and you boost the amplification in the camera (raise the iso), the noise is boosted also and so it may become more visible.

(the mark of better sensors and circuitry is that noise is not visible even at higher iso. Large sensors with relatively low megapixel counts like the Sony A7s can get great shots at insanely high iso because each pixel is larger, has more receptors/pixel and thus there is less average random noise/pixel))​

If the image is under-exposed and you boost the signal in post-processing, the noise in shadows, where signal to noise ratio is not as great, becomes visible.

 

[BillM]

Great advice already given, I was just going to stress the metering too. Try again with spot metering, AF-S, single focus point and expose for the face, you'll see a big difference in the test photo's.

 

[MichelleP]

Thank you all for your replies! I use af-s and single point focus and will switch to spot metering and try some more test shots with better exposure for the face. My Active D lighting is set to auto. Does Active D lighting. affect a RAW image? I shoot in RAW.

 

[Derrel]

Active D-Lighting writes an instruction set that "tells the software" how to interpret the raw data, and how to display the photo. The scene your daughter is in, with the bright, sun-lighted areas behind her, and then her in open shade, that is tricky light! That is **exactly** the type of scene that Active D-Lighting was designed to handle, by adjusting the light metering AND the image processing (black point, and tone curve most especially) parameters to allow high-contrast lighting situations to be imaged successfully, without extensive user input in post-processing.

At 400 ISO with the D90, in the shaded areas, like your daughter's face, on a 100% crop, you probably WILL see the noise structure that that camera's sensor has at 400 ISO in the shade, on that level of exposure, with that type of a black point and curves adjustment. If you had deliberately OVER-exposed her face, the noise structure of the sensor would be almost totally masked, but the background would have been utterly burned out.

In the earlier days of d-slr cameras, that type of a scene would have had her rendered as an almost-black silhouette, OR her perfectly exposed, and the background utterly over-exposed to a point beyond recovery. The scene you shot here is the exact type of scene that Active D-Lighting was designed for. it is a very tricky exposure scenario, unless fill-in light is brought in to bring her "up", closer to the background light level.

 

[Ysarex]

Thank you all for your replies! I use af-s and single point focus and will switch to spot metering and try some more test shots with better exposure for the face. My Active D lighting is set to auto. Does Active D lighting. affect a RAW image? I shoot in RAW.

Yes. ADL does effect a raw capture. Raw sensor captures are not processed and so the ADL processing is not in any way applied to the raw file. It is applied to the camera JPEG. However to achieve the JPEG processing ADL deliberately underexposes the raw sensor capture.

Joe

 

[vintagesnaps]

The mixed lighting in the dappled sun could be tricky, and I think it's going to give you areas of light and dark on the subject. Sometimes if I'm in lighting that seems 'iffy' or changeable (sun's in and out) I'll get more than one shot varying the settings by one stop each way.

In the second one where she's in the shade, look at how sunny the background is, the meter is probably reading that light coming in not just the amount of light in the shade in front of you. I sometimes will lower the camera somewhat to get a meter reading of the subject more than so much of the background, then I get the camera set, and reframe and focus.

With these outdoors on a reasonably bright sunny day I'd lower the ISO, probably 100-200 would be high enough (when it's bright you don't need as much light sensitivity). For this you wouldn't need that fast a shutter speed unless she's going to start doing jumping jacks! (you'd need a fast shutter speed to freeze action if she'd be moving around).

I usually use manual settings so I rely on the meter to indicate if I have everything set to get the amount of light I need coming into the camera for a proper exposure. I also sometimes move around and change my vantage point a little to get the light coming in a little differently(depends on the setting, the time of day, which way you're facing, etc.).

 

[MichelleP]

[/QUOTE]Yes. ADL does effect a raw capture. Raw sensor captures are not processed and so the ADL processing is not in any way applied to the raw file. It is applied to the camera JPEG. However to achieve the JPEG processing ADL deliberately underexposes the raw sensor capture.

Joe[/QUOTE]

Reading this was an "ah ha" moment for me. It seems my camera light meter indicates at least 1/3 stop over exposure in order for me to get a correct exposure. Should I turn off ADL or just keep in mind to expose up to get it correct?

 

[Ysarex]

Reading this was an "ah ha" moment for me. It seems my camera light meter indicates at least 1/3 stop over exposure in order for me to get a correct exposure. Should I turn off ADL or just keep in mind to expose up to get it correct?

ADL doesn't alter the way your light meter indicates a reading. I think you're saying here that you get a "correct exposure" when the light meter is indicating a +.3, which has me scratching my head because you said you were shooting in AP mode. How are you determining what constitutes a correct exposure? Are you shooting in AP mode and using the exposure compensation function to set a +.3 exposure increase?

You noted that you plan to try spot metering. Nikon advises that ADL is best used with the camera set to matrix metering.

Derrel's observation is correct in that ADL was designed as a software addition to deal with processing very high contrast lighting conditions. Your photo with your daughter in shade against a sunlit background absolutely qualifies and the ADL function will generate a much better JPEG. That special processing can't be applied to the raw sensor capture.

This is a common feature now in modern cameras. Canon calls it HTP (highlight tone priority), Fuji calls it DR (dynamic range), etc. They all implement this function similarly by reducing exposure of the raw capture. If the high contrast light of the scene would have clipped highlights in the raw capture then this exposure reduction is beneficial as those highlights are saved from overexposure. If the highlights would not have clipped in the raw capture then the exposure reduction is detrimental as the overall dynamic range of the sensor is reduced and less data is recorded in the shadows.

If you want the camera JPEG then these functions are very beneficial. If you only want the raw file; then these functions may be either beneficial or detrimental depending on the final exposure of the raw file. NOTE: this is typically an either/or option in that it's unlikely that you'll have the best of both. Typically these functions deliver raw captures that could have been exposed more and so aren't "best possible." If you're not sure about the exposure of the raw capture and you want to be certain not to clip highlights then by all means hedge your bet and use ADL in high contrast lighting. If you are sure about the exposure of the raw file then you should have already decided not to use ADL.

In other words, ADL serves two purposes:
1. A better JPEG from the camera.
2. Cover my butt because I'm not sure I've nailed the exposure for my raw sensor capture and I'd rather underexpose than overexpose

Joe