Is ISO 100/200 really the Holy Grail?

[Starastin]

I was talking about full auto ! but yes - used to use auto iso. still the problem with at least canon was that it would choose iso100 & f2.8 rather than iso200 and f4 , which I would've preferred .

nikon / sony native iso is 200 , canons - 100 . probably some nikons like d3x has a native of 100 , don't know.

haven't tried the iso step stuff either. but on the other hand , haven't inspected how bad is iso320 for example either.

 

[Jelster]

Well I never knew that. I assumed this would be effectively a progressive (although exponential) scale. What is the reason for this, assuming you don't need a PhD to understand this?

Tim Dodd mentioned it on a thread a month or two ago. It seems that if you select IOS 250, the camera actually selects ISO 400, and ten underexposes by 2 stops, creating a greater amount of noise..... Not good.

Steve

 

[Rogdodge]

Tim Dodd mentioned it on a thread a month or two ago. It seems that if you select IOS 250, the camera actually selects ISO 400, and ten underexposes by 2 stops, creating a greater amount of noise..... Not good.

Steve

Ah okay, interesting. Easy to stick to the set values which I will in future. Thanks for the reply.

 

[Lawrence F]

I didn't know this either about stepped ISO settings, perhaps that explains the un-explained odd shot that has more pronounced noise where others don't! Good info, thanks Steve, I'll stick to the standard ISO stops in future too.

 

[lensflair]

Tim Dodd mentioned it on a thread a month or two ago. It seems that if you select IOS 250, the camera actually selects ISO 400, and ten underexposes by 2 stops, creating a greater amount of noise..... Not good.

Steve

By underexposes by 2 stops you mean it takes the shot at 400 ISO and then reduces the captured exposure somehow? It certainly doesn't do it by changing shutter speed or aperture.

I'll have to investigate this further becaused this would mean that when I use auto ISO and it sets it at say 1250 ISO, it is actually taking the shot at 3200 ISO. I have my camera set to not go over 1600 ISO most of the time when trying this and I certainly didn't see the kind of noise I would expect that high. I know the D3 is pretty good at high ISO but I would be surprised if that was the case.

 

[Starastin]

Tim Dodd mentioned it on a thread a month or two ago. It seems that if you select IOS 250, the camera actually selects ISO 400, and ten underexposes by 2 stops, creating a greater amount of noise..... Not good.

Steve

when you say it like that - it makes perfect sense. they develop 100, 200, 400 etc and only in auto the camera shoots iso160 etc . which - looks awesome if you remember film iso160 as it was the perfect portrait speed.

 

[lensflair]

This whole non-native ISO thing is interesting and I have been investigating it further.

It seems it is entirely possible that the actual 'native' ISO varies for different cameras and the manafacturers are very vauge about it all. It also seems that when you don't use full stop increments (ie 200, 400, 800) the camera may overexpose and pull the exposure down or underexpose and push it up. For example ISO 160 might actually be ISO 200 thats been pulled down, while ISO 130 might be ISO 100 thats then pushed up. The result being the ISOs that are pulled down can actually appear to contain less noise than a 'native' ISO thats lower. There are some interesting tests that show the canon 5DMKII to have less noise at ISO 640 than at ISO 400. But you will be losing dynamic range and could clip the highlights because it's actually using ISO 800 and pulling the capture down to ISO 640.

I should point out that these test were done in video mode and that throws a whole load of other variables into the mix. A lot of people claim the on sensor amp that sends data to the analog/digital converter has a fixed gain, hence the so called native 'native' ISO's, but an amplifier on the ADC can then increase or decrease this signal digitally, eg ISO 130would be ISO 100 followed by a 1.3x amplification and ISO 160 would be ISO 200 with a 0.67 amplification.

So how much does this affect the amount of noise and the resulting IQ? Well I think it will probably depend on the camera, I have done a quick and dirty test with a nikon D300, put the camera in manual mode, manual focus pointing at a mid tone wall in dim light (2 second exposure at f2.8 ISO 200) and defocused the image. Shot each ISO in 1/3 stop increments from lowest I could go to ISO 3200. I adjusted shutter speed to maintain the same exposure between shots. The noise increased as ISO increased and I didn't see a 'non native' ISO producing more noise than the ISO 1/3 higher or lower in any of the shots.

I'm not saying there isn't measurable effects or that if you want the best IQ you should use 'non native' ISOs, but for me I can't see anything that will stop me from using auto ISO and 'non-native' ISOs. I am going to do a better comparison when I try it again with a D3, but I can't imagine it is going make me change my practices at this point. The convinience of selecting the aperture and shutter speed I want seems worth any extra noise or loss of dynamic range I might be getting.

BTW If a second amplifier is used to obtain the non-native ISOs, why can't we choose any amplification factor we like? I guess it makes sense to stick with the same increments as shutter speed and aperture though.

And I'm not sure calling it 'native' ISO is really correct, If the signal from the sensor was amplified by x1 that would be it's native ISO right? But I expect that never actually happens and the native sensitivity of the sensor would actually be some oddball integer ISO? I think the lowest ISO that they recommend (200 for most nikons and 100 for most canbon) is probably the standard ISO they found gave the best results?

 

[redhed17]

I never used Auto ISO as all it tried to to do was give you 1/60th sec whatever the situation, which was maybe OK when all there were were 35mm with say a 50mm lens, but most cameras now have a zoom lens on, so the 1/60th minimum shutter is no longer applicable for the most part now imho. :shrug:

However, when I got my new camera it had a more flexible Auto ISO were I can set the slowest speed and the highest ISO the camera will use. I think Pentax were the first to have a flexible ISO setting.

Even though I'd had my camera for awhile, I used the configurable ISO setting on my camera for the first time when walking through the narrow alleyways in Venice, were you could turn a corner and be in a bright open square, or an alleyway that is even darker. Messing around changing ISO constantly was a pain the first time I went, but the last time I could just concentrate on taking the pictures until I needed to take over and adjust the ISO.

I've also used it in other situations like when I was taking pics of motorcross last weekend, were I wanted a minimum 1/1000th sec shutter. The exposure could change quite significantly whether zoomed in on a a rider in a dark outfit, or a wide view of the light dirt, setting 1/1000th as the minimum shutter speed, and the lens on the widest aperture, with the configurable ISO I did not need to make changes and could concentrate on timing and focusing the pictures. Which was hard enough.

I think more and more cameras will have flexible ISO settings, as even though the ISO performance is getting better, you still want the lowest ISO setting for the given situation. In changeable light, just setting the ISO to say ISO 1600, could still mean the aperture or shutter could be changing automatically depending on what mode you are in. :shrug:


And as for native ISO, isn't it the where the sensor gives the lowest noise and the largest dynamic range? I read a thread during the week which said the Lo ISO (ISO equiv) setting on my camera may give less noise, but looking in to it, the dynamic range was slightly compromised. The ISO on my camera seems to be the optimum.

Obviously the manufacturer of the sensors tries to get close to 100 or 200, but in reality may not be exactly either. :shrug: The manufacturers, and the photographers for that matter, like to work in round numbers for the most part.

 

[lensflair]

Yeah the auto ISO feature on my nikons allows you to set your base ISO (say 200), the highest ISO you want it you use and not go over (say 1600), and the minimun shutter speed (I might set that at 1/50 for a 50mm lens). The camera will choose the lowest ISO possible given the aprture you choose and how much light there is, but if your shutter speed was going to drop below what you set as your minimum it will raise ISO to prevent this. It will only raise it enough to keep the shutter speed from faliing below the minimum you set.

If you are in reasonable light it may never increase the ISO, but if you point the camera somewhere dark and/or use a smaller aperture it might increase it a little to maintain a correctly metered exposure without dropping below the minimum shutter speed. It doesn't just randomly select high ISOs for no reason and you can see the ISO being chosen in the viewfinder.

 

[Dave Pickett]

one big benefit of auto ISO is that I can set my camera up (normally for horse show jumping or cross country) and my daughter can use it all day - if the light changes the camera sorts it out!
On my D90 and 300s I set min shutter of 500th or 640 then base ISO 200, max 1600 and leave camera in program mode. Set like this any surplus light is used to increase dof and shutter speed in unison which helps with moving targets! It's a great way of working, wouldn't be without it.

 

[Zarch]

I'm pretty happy with auto ISO now I understand why its choosing what it does.

I am also now pretty happy shooting at higher ISO if it means a sharp image as i've just discovered Noise Reduction in Lightroom.

Thanks for all the help in this thread, very much appreciated.

 

[Scorg]

I guess it really does come down to the subject mater and what is intended with the image when finished.
I had to shoot in a lowly lit room last where flash was banned and was really forced upto iso3200.
Was rather fearful how these images would turn out, on the small preview screen they looked okay, but that cannot be trusted. so back home for proper editing and while it was rather noisy it ended up still being a usable image, the capture itself was what became important over quality.
But with a bit of Post Processing to clear up the noise and the part where the image was used in print form then the original viewed noise then nolonger became an issue, it looked rather good just on the print that had been made.

 

[big soft moose]

I must admit I rarely go below 400 on my 20D - its really my default setting to the point that i have to remind myself to turn it down when i'm trying to get a slow shutter speed on a sunny day.

Back in the film days I used nearly always use Provia 400F (or high speed 1600 B&W )

 

[gongua]

Better have an granny image than an blurry image, or if possible use tripod to use the lower iso possible.

 

[Spuff]

Better have an granny image than an blurry image, or if possible use tripod to use the lower iso possible.

I've got quite a few images of blurry grannies. Where am I going wrong Gong? Should I get a tripod from the classifieds?

 

[petersmart]

I have zero problem using up to 1600 iso with the option to go higher if necessary. If I pixel peep I'm not happy with loss of detail over 3200 so I don't pixel peep up there.

BTW Dean the 1Ds II I bought from you is still going strong and producing great shots!

Have now taken over 3500 shots without probs and love the solid feel of it.

A lovely camera to use.

.

 

[SW3105]

I'm so glad I read this thread, it makes me feel much better! I also have the D3100, mostly my photography is of my 2 young daughters and generally indoors with the windows being the only light source. I mostly use Aperture priority mode with the aperture wide open as I like a shallow DoF, in order to get a good picture I have to set the ISO to anything above 800. I'm getting great results at 1600 with very little noise.

 

[Zarch]

I'm so glad I read this thread, it makes me feel much better! I also have the D3100, mostly my photography is of my 2 young daughters and generally indoors with the windows being the only light source. I mostly use Aperture priority mode with the aperture wide open as I like a shallow DoF, in order to get a good picture I have to set the ISO to anything above 800. I'm getting great results at 1600 with very little noise.

You might want to think about getting the 1.8 35mm lens for indoors as you can get even more wide open than the kit lens.

I'm not saying the composition of these shots are any good (and the WB needs sorting), but they show you can what you can get on a D3100 with the 35mm at 1.8 in a poorly lit room.


DSC_0216.jpg by Zarch1972, on Flickr


DSC_0236.jpg by Zarch1972, on Flickr

 

[SW3105]

You might want to think about getting the 1.8 35mm lens for indoors as you can get even more wide open than the kit lens.

I am thinking about a 50mm, Nikon have announced a new 50mm 1.8 AF-S prime lens, prior to this announcement, I'd pretty much settled on choosing the 50mm 1.4. And now that you mention it, I wonder if the 35mm might be better as most of my better pictures are shot at between 40-50mm ... I think your WB is fine actually.

 

[whiteflyer]

The holy grail on a Canon 5D II is actual ISO160, or so I read at the weekend as this is the native ISO for the sensor.

But as has been said many many times a sharp image with high ISO noise is better than a blurry photo with no noise.