# Does ISO effect Image sharpness?



## AfternoonTea (May 20, 2013)

I know sharpness has many factors such as lenses, sensor, resolution. I also know that A smaller ISO setting has less noise than a higher setting so a smaller ISO in theory gives _apparent_ sharper images than a higher ISO value. Lets say if we were to narrow it down to a controlled environmental setting. Lighting is perfect, and lets fix the F-stop to the same setting, and its sweet spot.

Our camera is on the tri-pod; We are in focus, depth of field, white balance, everything is set . The only thing we need to change is the ISO, and Shutter speed which can compensate to our perfect lighting and no compromise with F-stop is needed. 

My question is does ISO really effect overall image sharpness? 

Before posting this I read many things, and previewed tons of photos on flicker and compared there specs. Does ISO matter in terms of sharpness with the controlled. Obviously ISO 1600+ will look very noisy. So lets stay around ISO 100 or less - 800. 

I typically like ISO 100 (in good lighting, and compensate the shutter) since its the least noisy on my camera, but will bumping it up (causing more noise) effect its sharpness? I read that ISO noise does not effect sharpness that a sharp picture is a sharp picture, and its  (not literally since its cause by technical things)  almost like noise (grain) added over a picture.


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## waterbeef (May 20, 2013)

Noise caused by high ISO ruins a photo.
Sharpness is meaningless to a ruined photo.


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## Benco (May 20, 2013)

Depends whether you want a given level of noise in the photo, applying a lot of noise reduction to high ISO photos will soften them.


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## spmakwana (May 20, 2013)

ISO have nothing to do with sharpness of photo, more ISO the more noise.


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## runnah (May 20, 2013)

waterbeef said:


> Noise caused by high ISO ruins a photo.



Well that is just subjective.

Anyways. It's all about finding the balance in the given situation. Just leaving the ISO on 100 and expecting sharp images will give you bad results, and vice versa with high ISO. So read up up on which lighting situations call for which ISO.


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## CaptainNapalm (May 20, 2013)

High ISO does not take away from image sharpness.  Post processing to reduce the noise caused by high ISO setting does.


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## DSRay (May 20, 2013)

It seems to me, the best way to answer your question is to try it; you'll never know until you do.


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## curtyoungblood (May 20, 2013)

I tend to push my ISO abilities to the edge, and I do tend to feel like it is difficult to get really crisp photos at a higher ISO. However, this could be related to the quality of the light, AF having trouble in low light, etc.


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## TCampbell (May 20, 2013)

If you're shooting in JPEG, then the answer is yes.  If you're shooting in RAW then the answer is "maybe" -- it depends on what you do in post processing.

When you shoot in JPEG, the camera will automatically reduce noise.  You can often see this happen at specific thresholds.  For example... I've seen ISO/noise graphs which show the camera going from 100, 200, 400 with each step having progressively more noise (albeit a small amount) and then at 800 suddenly the camera has less noise than it had at 400.  That's because at 800 the camera kicks in a specific aggressiveness of noise reduction.  It'll go up a few more stops and then kick in an even more aggressive reduction.

Noise reduction has the side-effect of softening an image.  

However... if you're shooting in RAW then there's no built-in noise reduction.  Any noise reduction that occurs would have to be done in post processing by you.  You can decide whether or not you perform noise reduction and how aggressive you want to be.  Technically any level of reduction will soften the image somewhat... but no reduction leaves aberrant pixels which you generally don't want to see.  I don't fully cook out the noise... I tend to just try to process it down somewhat (and to do that, I use a plugin named Imagenomic NoiseWare Pro -- which offers more control over how the noise gets reduced.)


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## KmH (May 20, 2013)

AfternoonTea said:


> *Does ISO effect Image sharpness?*


No. At least not directly.
Many DSLR cameras today perform quite well at ISO 1600+
But you probably don't yet understand what sharpness is, a combination of acutance and resolution.

Acutance is about how quickly image information transitions at an edge. Lens quality and post processing affect acutance. Image sharpening alters/enhances acutance. 
Resolution is about the camera image sensor's ability to show closely spaced details.

Image noise comes in several forms and can be an issue even at ISO 100 if an image is under exposed, or has dark (underexposed) areas.

At higher ISO settings making sure the exposure is accurate helps minimize image noise.
For digital images, at any ISO setting, the best results are generally attained when we Expose-To-The-Right (ETTR) on the histogram.

Tutorials ? Sharpness
Digital Camera Image Noise: Concept and Types

Understanding Histograms, Part 1: Tones & Contrast
Understanding Histograms, Part 2: Luminosity & Color
ETTR
Optimizing Exposure


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## Tailgunner (May 20, 2013)

CaptainNapalm said:


> High ISO does not take away from image sharpness.  Post processing to reduce the noise caused by high ISO setting does.



I'm really new but this makes sense to me. I mean you loose a certain degree of sharpness using glass to begin with and offset this with the sharpness settings in your post process software. So it only makes that you could offset some ISO differences with the same sharpness feature.


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## amolitor (May 20, 2013)

Random remarks, in no particular order:

Resolution depends on the lens and the sensor. ISO doesn't matter, and neither does exposure. If I underexpose by 20 stops, I have just as sharp an image as when I expose correctly -- it just happens to be rendered entirely using black pixels.

Acutance is a different story, and the overall psycho-visual perception of "sharpness" is quite another story as well. The sharp but entirely black image exhibits no actuance at all, and does not appear sharp at all, of course.

Noise can actually increase the perception of sharpness, up to a point, and under certain circumstances. Noise can also increase the information content of an image, in certain cases, and in certain pretty specific ways. Information content isn't the same thing as sharpness, but it related.


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## HughGuessWho (May 20, 2013)

Using high ISO in and of itself does not effect sharpness. However, high ISO will introduce noise. The removal of that noise with noise reduction software will soften an image. Therefore, High ISO and image softness are indirectly related, I guess you could say.


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## jowensphoto (May 20, 2013)

waterbeef said:


> *Noise caused by high ISO ruins a photo.*
> Sharpness is meaningless to a ruined photo.



Subjective, but I'm still going to say not true. Grain can add to the image; I like it, a lot. I never turn my ISO below 400.


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## jake337 (May 20, 2013)

Is this sharp?

ISO 3200 on my D90


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## jake337 (May 20, 2013)

jowensphoto said:


> waterbeef said:
> 
> 
> > *Noise caused by high ISO ruins a photo.*
> ...




Agreed.  

I think a bad composition ruins more photos than anything.


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## cynicaster (May 20, 2013)

I can't remember where, but I read an article a few months ago where a guy who likes to shoot sports was saying that he sometimes shoots at higher-than-needed ISO because he feels a bit of noise enhances the "perceived" sharpness of an image.  Admittedly I've never tried this, but sounds like ******** to me.


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## Derrel (May 20, 2013)

More otherwise good photos have been ruined by slavishly sticking to ISO 100 than have been ruined by judiciously elevating the ISO to 320,or 400, or 500 when needed.

The idea that ISO 100 "always" leads to a better picture than a higher ISO setting is a common newbie way of thinking. The better d-slr cameras from Nikon today have sensors which yield superb results at up to ISO 1,000 or so, and then merely "excellent" up to ISO 3,200, and above that the performance is just "good".

One thing that REALLY builds noise is in-camera underexposure, which a lotta newbs often get.


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## jowensphoto (May 20, 2013)

Derrel said:


> More otherwise good photos have been ruined by slavishly sticking to ISO 100 than have been ruined by judiciously elevating the ISO to 320,or 400, or 500 when needed.
> 
> The idea that ISO 100 "always" leads to a better picture than a higher ISO setting is a common newbie way of thinking. The better d-slr cameras from Nikon today have sensors which yield superb results at up to ISO 1,000 or so, and then merely "excellent" up to ISO 3,200, and above that the performance is just "good".
> 
> One thing that REALLY builds noise is in-camera underexposure, which a lotta newbs often get.



OK, that got me thinking... it's the same with every exposure element. There are rules (IE: always low ISO, always fastest possible shutter speed, newbs assume wide open aperture is best, WB should always be neutral, etc) but when broken effectively can enhance rather than detract.

Like motion blur or "silky" water shots, slow shutter speed can add to a photo just as higher ISO can. Changing WB to the "incorrect" setting can achieve a warm or cool feeling - when applied to the correct setting (like a sunset), can change the entire mood of a photo.


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## AfternoonTea (May 20, 2013)

So really ISO does not directly effect sharpness (a sharp image is a sharp image), but increasing ISO in turns adds noise/grain (that may or may not be wanted) and filtering it may cause a image to soften? 

I've taken notes in the past which I'll just post below for ISO new comers

*ISO 100 *- Daylight, strong sunny days, beach days, Snow on the ground, Lots of light, and bright light. In addition *ISO 200* for more overcast 

*ISO 400 - *General use, Cloudy days, indoors for window light portrait, Rainy days, Sports

*ISO 800* - Evenings, sunsets, indoors without flash

*ISO 1600+ - *&#8203;Low light situation, rock concerts, night clubs, your kids school play 




*60D lab results *






60D users good ref for ISO noise tolerance
http://www.the-digital-picture.com/Reviews/Canon-EOS-60D-DSLR-Camera-Review.aspx


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## Derrel (May 20, 2013)

Uh-oh...now you're thinking!!! lol

EXACTLY, jowens...how many times have we seen the post that basically reads as follows: "I just bought a 35mm f/1.8 and took a bunch of family pics and a lot of them are blurry,"? Have there been more of those posts, or more of the, "I just bought a 50mm f/1.8 and took a bunch of family pics and a lot of them are blurry!" posts? My vote goes to slightly more 50mm wide-open garbage threads.

I often say that a sharp but noisy photo is far better than a perfectly-exposed, low-noise SMEAR. In the many years I've been involved in photo forums, I've long been an advocate for shooting at an ISO level that is one or even two f/stops ABOVE base ISO...simply because it gives the photographer more choices, more leeway, more 'cushion'. I seldom if ever want to shoot wide-open...I often want to shoot at f/4.5 or f/4.8 or f/5.6. With flash, I often want to pick up MORE ambient light in the background, so I recommend to people to do as I do when shooting indoor bounce-flash: START at ISO 400, and notch up to 500 or 640 or even 800 ISO if it is at all needed.

For bounce flash situations, a lot of popular flashes simply do not have the power to get the kind of shots you WANT to get when the camera is laboring away under the artificial ISO 100 limit. For flash event work, using ISO 400 or 500, it means the flash will recycle and be ready for the next shot much sooner, battery sets last longer, and people are not BLASTED with full-capacitor discharge flash dumps...but instead, just brief little 'winks' of flash.


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