Nikon 3100 Announced
 

This new Nikon camera shoots 720 24P/25P/30P and 1080 24P video formats with full autofocus. The price below is the list price, so I would expect the body to sell by itself for about $500 once it hits the stores in September.

Nikon D3100 Digital SLR Camera with 18-55mm NIKKOR VR Lens : $700 US

Nikon 3100 Web Page Detailing HD Video Modes

Lots of very interesting autofocus / focus-tracking modes. I would ignore the sample video for now, as it was probably made with a pre-production camera. ( the exposure looks a little wacky to me )

I'm curious if they have improved the aliasing artifacts.

Interesting little camera. The sensor claims to be physically bigger than a Canon 7D but has less pixels if I am reading the specs correctly. Does this mean it is more sensitive with bigger pixels? Does the HDMI output have a clean settings and does it stay on when recording video?

Nikon D3100 Sensor 23.1 x 15.4mm Nikon DX-format CMOS sensor
Resolution Total: 14.8 Megapixels, Effective: 14.2 Megapixels

Canon 7D Sensor 22.3mm x 14.9mm CMOS
Resolution Effective: 19.0MP, Recorded: 18.0MP

Manual control in video mode? I can't seem to find anything about it on the website. Am I missing something?

I think this is just another version of "canon t2i" I can not see any major improvement! maybe I am wrong it is a wait and see game for now.

I've never been a Nikon fan, so I don't know much about their cameras. But to my knowledge, they have always favored the larger sensor, and lower pixel count. I think this is part of the reason they have always been great with high ISO performance.

JS

Well, generally they are the same, but sensitivity isn't really what we care about most anyway: it's noise. And when it comes to noise, sensor size (not pixel size) is by far the most important factor (all else being equal).

Mic input?
 

Hmmm..... not one word about a mic input.

I just called Nikon concerning the new D3100 DSLR's HDMI output.

They state that the HDMI output is only active when playing back pre-recorded footage.

They state that one cannot use the HDMI output for "Live View", such as for composing shots or checking focus prior to recording.

They state the one cannot use the HDMI output while recording.

They were very confident that what they were stating was correct.

This appears to be confirmed by a very careful reading of the D3100's specifications.

This camera has no mic input, internal mic only.

Dan

But does that mean that it's deactivated by design and could theoretically be activated by going into the software/hardware, or is it just not physically possible for it ever to work?
I don't see any reason why it should not be active while recording, there isn't much/any extra processing needed is there? Dan, you'd know a lot more about this than me, should it be feasible? It'd certainly make a HUGE difference, as the codecs on all these DSLRs are a bit iffy to say the least.
Steve

Dear Steve,

When I first read the spec's for the D3100, it appeared that they were saying that the HDMI output only worked in Playback Mode.

When I called Nikon, I asked if the HDMI output was active for "Live View" and while Recording.

The person understood the question, then put me on hold.

When she came back, she stated it very clearly that the HDMI is only active for Playback.
She explained that the camera goes into a different mode when the HDMI output is activated.
In this mode, one can not take a picture, or record a movie, or even see the live image via the HDMI output.

She was very confident in her details as to how this worked.

I was rather surprised by this.

I think we will have to wait for detailed reviews to learn more.

Here is Nikon's wording:

Is it possible to play recorded movies on a TV monitor?

If an HDMI terminal is incorporated in your TV, movies you have recorded can be played back by connecting the camera and the TV using an HDMI cable. 1,280 x 720 and 1,920 x 1,080 (16:9) modes are suitable for HD playback

Any processing power or other other reason why playback is different to recording Dan?
Doesn't seem to me that there is anything extra to be done to show the live view image on the camera's screen and at the same time output a feed through HDMI, or am I missing something? It definitely sounds to me that they've chosen to disable it rather than been forced into it.
Steve

Dear Steve,

I do not know why they would have eliminated HDMI out for Live View and while recording.

For us, it certainly makes the camera more useful when these are included.

One possible technical reason would be memory capacity. Nikon does describe this as an "Entry Level" camera.

The Nikon representative indicated that the D3100 goes into a different mode, when the HDMI output is activated.

We do this on the nanoFlash. We reboot the nanoFlash, using different code, when certain options are selected in the menu.

For example, our MPG support requires one of these Reboots, which only takes a few seconds.

This allows us to have more memory space available to perform the requested tasks.

When one selects MOV or MXF, we reboot the nanoFlash into code specific for both MOV and MXF. (There is no reboot when switching from MOV to MXF or back.)

We also reboot into different code for 3D mode.

In 3D, we have eliminated support for Standard Definition, thus freeing up room for 3D features, such as Image Flip, Image Flop, and image combining functions.

We do not expect anyone will want to shoot 3D in SD.

Being their most entry-level D-SLR, I think they disabled the HDMI Out when recording on the D3100 intentionally so that they can try and motivate people to buy their future 1080p cameras (surely there will be a D90 with 1080p soon) which will probably have the feature enabled.

10 minute clip length, only 720P at 1920 x 1080. Canon doesn't need to worry about this one.

I didn't think any of these vDSLRs had the option to record via HDMI? Even the Canon 5d and Nikon D3s - is that not correct?
Steve

Dear Steve,

As of this date, most all DSLR's, at least those that I am familiar with, were not designed with recording from the HDMI output in mind.

I expect this to change, as the camera manufacturers, at least some, see the advantages of providing a high-quality image to be output via their HDMI.

This allows an external device, such as our nanoFlash, to be able to record:

1. For a longer period of time.
2. To record at a higher quality. i.e. a higher bit rate or using a differnt codec.
3. To record in different file types (MOV, MXF and others).
4. To reduce heat buildup in the cameras during long recordings.
5. To allow their cameras to be more widely used.


The technical challenge is reducing a high pixel count down to HD pixel counts, such as 1920 x 1080 while peserving image quality. Simple line skipping or pixel skipping does not achive a very high quality image for the HDMI output.

But this conversion to 1920x1080 is being done anyway in camera to record to the on-board card yes? So there is an HD compliant signal to put of of the HDMI in playback, should be easy to do during record too?
Steve

Dear Steve,

You have a very interesting point.

The Canon 5D Mark II does not put out 1920 x 1080 via the HDMI output, at least the image size is not the full 1920 x 1080. But the internal recordings are 1920 x 1080.

The key question is image quality. These cameras were never designed to put out a high-quality image via the HDMI output.

Since there is a demand for high-quality images out of these DSLR's, I believe it will come.

I assumed that what came out of the HDMI was what was recorded by the camera after it had been through the codec. And by that rationale, if the image through the HDMI is not good then the image recorded to card will be worse.
Steve

Dear Steve,

On video cameras, the HD-SDI or HDMI input is almost always before compression.

I do not know the signal path of DSLR's. I would not be surprised if some are prior to compression and others after compession.

The D95 in September should sort all this out.

It's been confirmed that the D90 is being replaced by the D7000.

Duncan.

But doesn't the size of the photosite (the thing that captures the 'pixel') effect the signal-to-noise ratio, and therefore aren't bigger photosites better? Isn't sensor size only important if it allows you to increase the size of the photosites (ignoring electronics and optical limitations.) That seemed to be what people were arguing a few years back: Enough already with the megapixels

I think you meant 1920 x 1080p24, otherwise that is an incredible frame rate!

Yes, that's generally true for low light (high ISO), but the effect is much, much smaller than is generally assumed. The reason that most people think it is such a large effect is because they make a lot of mistakes in analyzing image noise, such as confusing the effect of pixel size with the effects of sensor size, or measuring different spatial frequencies as if they were the same ("100% crop").

For example, quadrupling the sensor area has a huge effect on noise, allowing you to increase ISO by two stops for the same noise level (use ISO 1600 instead of ISO 400). But quadrupling the pixel area (without increasing the overall sensor area) only allows you to increase ISO by a little bit for the same noise level, maybe 1/3 stop. (The amount of improvement corresponds to the nonlinearity of the scaling relationship between spatial-frequency-normalized read noise and pixel diameter.)

In some cases, there is no benefit at all. For example, the 5D2 has about 1.3 stops less noise in low light than the 7D (illustrating the benefit of overall size). But if you crop the center portion out of the 5D2 (so that the sensor size is the same as the 7D), the noise level is about the same (slight advantage to the 7D, actually). In other words, even if the 7D had the 5D2's larger pixels, noise would not improve. But that is only because of the specific implementation of those two cameras.

The central point of the article seems to be that pixel count alone is a poor indicator of low light performance. I agree with that.

There are some other points in the article that seem to contradict what I'm saying, but really they don't, it's just a different way of looking at it. For example, as an analogy, one of the points made in the article is that larger pistons have more horsepower than smaller pistons, so if you have a certain number of pistons, then larger pistons give the engine more horsepower. I think that's a backwards way of looking at things. What I'm saying is that larger engines have more horsepower than smaller engines; piston size has an effect too, but the effect is much smaller than engine size.

The article does have a few errors, such as where it says that larger pixels hold more charge and that this improves SNR. Actually it that improves dynamic range (SNR at maximum S), which has no effect on low light performance. For context, the benefit of such would only exist if the larger pixels were part of a larger sensor, therefore it is the sensor size, not pixel size, that causes the ultimate benefit to dynamic range. If the sensor size remained the same, then the total charge for a given level of detail (spatial frequency) would also remain the same. (Hence why smaller pixels on an equal-sized sensor do not generally have less dynamic range, at least in the 2-12 micron range.)

The article also cites an example where an older, large pixel camera has less noise than a newer small pixel one. That is pretty rare, so I would guess the author either made a measurement error or just happened to pick one of the exceptions. Almost any other such comparison would show noise remaining the same or improving (e.g. from 10D -> 20D -> 40D -> 50D -> 7D).

Surely "quadrupling the pixel area without increasing the overall sensor area" must mean roughly decreasing the overall no of pixels on the sensor by a factor of 4?

Thanks for catching my mistake. That was a pretty bad keyboard 'spasm', I meant "only 720p if you want 30fps."

Yes. So the idea is that a 7D with 4.5 MP would have had slightly better low light performance, but a 7D with 72 MP and double the sensor width would have dramatically improved low light performance: two stops higher ISO for the same noise level.