Nex High ISO advantage is larger

Started May 26, 2010 | Discussions thread
zackiedawg
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HHT and AMB - more information
In reply to papillon_65, May 26, 2010

papillon_65 wrote:

I haven't seen it in action but people walking would be a common scenario where I would doubt it would help…that seems to be of limited use to me. I'm sceptical as to how useful this is.

Just thought I'd add some info here, if it helps. As someone not looking to buy a NEX camera, I can add a somewhat objective bit of info here on the special features HHT and AMB.

These features have been around for a year or so in Sony's P&S models. Those models are using the vestigial 1/2.4 sensors with 10MP - obviously a nightmare for noise and NR smearing at anything but base ISO. I was curious about these new features to see if the camera would be usable at higher ISOs. The verdict - they work, and really make these by far the best high ISO compacts ever made. With caveats, as usual.

First - Twilight mode: This is the 6-frame stacking mode for basically non-moving scenes. I say basically...it's even usable for a portrait if you warn the subject to try to be reasonably still for a 1/2 sec. The camera uses just enough ISO to achieve proper metering after considering the effects of the 6-frame stack. In a situation that might require ISO1600 in normal mode, the camera can get away with ISO1250 in HHT - the stacking eliminating noise, increasing detail, and providing enough shadow detail to make the ISO level usable. The difference in detail over straight ISO is quite impressive, as is the low noise. I can only imagine how much better it would be on a larger sensor like the NEX. Here's a 100% crop from a straight ISO1600 shot with the TX1:

Here's ISO3200:

And using twilight mode, which selected ISO2500 to give roughly the same exposure as ISO3200 did:

You can see the fireplace screen detail, the back of the blanket, the wrinkles on the leather chair arm, the brick detail, etc are all best in the twilight mode version...even better than ISO1600. Noise is lower, and edge detail is better. Remember, this is off a cheesy miniscule sensor and a lens half the size of a dime...NEX should be worlds better than this.

AMB mode performs the same trick...but the difference is that it will usually start with higher ISOs to make sure the shutter speed will be faster than 1/250 if at all possible, then lower the ISO if it can achieve a fast shutter speed and properly expose. It shoots 6 frames, and stacks & aligns them the same way - but it will look for motion within the scene, and if a subject moves through the shot, it will only use a single frame of the 6 frame stack for that part of the photo. Anything not moving will be stacked. The end result is a 6-frame stack shot with the resultant better noise control and detail, except the moving subject which is rendered as a standard high ISO single frame. The subject will not be blurred or ghosted...but will be noisier and have less detail, at least up to the capability of the camera. With the NEX APS-C sensor, that should mean still quite usable to ISO3200 or so with respectable detail and noise control...with my little ultracompact, that limit is more like ISO400 - above that, the subject will be pretty noisy. But still usable, as at least nothing is blurred.

I've tested AMB mode on my fidgety cat at ISO3200, and gotten surprisingly good results considering this is an ultracompact camera handheld:

Like any cat, she twitches, fidgets, etc. It was a bit of a technique, to make a little noise to get her to look at me fairly still just long enough for the 6 frames...a more drastic movement on her part would end up looking exactly the same, except the cat would be much noisier and show the NR smear from high ISO, since it would only be from the 1st frame.

Here's AMB in an outdoor scene - the whole scene stacked fine since it wasn't moving, except the blue jay - who pivoted 90 degrees and flew off as I was shooting. It's ISO640 (showing how AMB will start to back off the ISO when it can, but keeping the 1/250 shutter), and looking at the full-size shot, I can see that the bird likely only got at most 2 stacked frames before it moved...it's a bit noisier than the rest of the shot, and has a little detail loss in the feathers from NR that would have been restored if stacked:

Now, take all of that info, and imagine getting to do it with an APS-C sensor rather than a 1/2.4 sensor. One thing I'm fairly certain of - Twilight mode and AMB mode are going to produce killer results at high ISO. Any stacking of frames, in camera or post processing, will reduce noise and increase detail. That's why the technique has been used in astrophotography. It works. It is another tool to use at high ISO - it won't work in some situations, like extreme movement - but it isn't taking away regular high ISO use. It just offers another option when the situation is right for it. That's how I use it myself. In fact, on my A550, I use the 'HDR' 2-frame stacking mode sometimes at high ISO if I'm shooting a static scene - because it will reduce noise and increase detail, so why not use it if you can? It can even allow use of the otherwise ridiculous and unusable ISO12800 on the A550:

While ISO6400 is pretty solid and I use it a lot, not many cameras have a usable ISO12800. And this is a quickie handheld sample shot at F2.0 (super shallow DOF, which is why the near bottles are OOF). But the color, detail, and lack of noise make even ISO12800 not bad at all, and far superior than a standard ISO12800 shot, all by using the HDR mode at the lowest setting.

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