Near-simultaneous isn't sufficient when you have moving subjects in low light.


None -- I'm not using a fixed focal length lens, and I don't crop images. Or rather, when I crop images, I do so because I want to change the aspect ratio, not to crop-and-zoom. I don't do digital zoom.
Many. But that usually has little to do with the focal length, and more to do with needing to be 6 feet higher in the air, or 8 feet to the left, or transported to the middle of the auditorium from where I am at the front of the stage.

But the rest looks very nice.

My answer to that is "it depends". Some scenes, I'd be quite confident that I have all the time in the world to swap lenses, and not miss anything important. Heck, I could saunter from the stage front to the sound booth for a shot to capture an overview of the staging/blocking, and not miss anything terribly exciting. Other times, thinking back to some of the scenes I've shot, I'd be attempting to change lenses in the dark, while on the move, navigating around people, stairs, and auditorium seating. Not doing this on a daily basis, I'm not so confident that I'd get that swap down in time, before I have to be where I want to be for the next shot. This is where having that staged shoot would come in handy, as I'd just switch lenses and have them re-run that part of the scene.

I've never been one to worry about dust. I've swapped lenses in a windstorm, while at the Oregon Sand Dunes. My wife wasn't so thrilled with that.

That bag looks awesome... thanks for that pointer. That's a case (NPI) where having the right gear is helpful. My camera bag is a backpack style bag, with a side-pocket access. It's great for walking around on a family outing, but not so great when you're in a single location for a few hours, needing rapid, frequent access while on the move. But then, like all of our gear, we really bought it for the former, with the theatre work being a secondary use.

It's all been a huge learning experience -- I've only been doing theatre photography for ~4 years, and it's been 100% learn-as-you-go, so I guarantee you there's lots I don't know about the subject.

The great thing about that bag is it's silent! No zippers or velcro (well there is but it can be silenced), for me it's ideal.

Changing lenses becomes as easy as changing gear, I don't even notice it now. You can also anticipate the lens you'll need most of the time. I shoot weddings, so the risk of missing moments isn't any greater. But having the right bag is key, without the LC3 my photography life would be much harder. I have tried a shootsac before but it grips the lenses.

I put small cotton flannels in the bottom of the 3 LC3 compartments, I can then just drop stuff into them without thinking. The rear compartment is big enough for batteries, a flash gun, flash trigger of some sort etc... Also has a slot of business cards which is really really useful to be honest.

I have a larger shoulder bag that I transport things in, it stays in the car now with the spare bodies etc... and the LC3 sits on top of everything.

Cheers

Cris

Sounds like a good rig for your needs!

Can you elaborate a bit more on this? This is very interesting.
I understand what you're saying, but isn't that true only limited to one specific sensor? In other words, if you take SensorA and shoot at ISO 800 instead of ISO 100 specifically to reduce the time the shutter stays open, then you are obviously exposing SensorA to less photons, therefore losing information (high bit will be zero) compared to a longer exposure at ISO100.
But, aren't different sensors responding differently? Isn't the point of sensors/cameras reaching ISO 25.000, for example, precisely the ability of those sensors of retaining more information out of that shorter exposure to photons?

In other words, would I be wrong in assuming that a Canon 5DIII "SensorB" will have LESS zeros at high bit at ISO 25.000 at 1/320 shutter speed, for example, than the Nikon D800 "SensorA" at those same settings (if it could reach that high ISO)? If so, then I'd rather have that possibility, which I assumed was the whole point of such sensors compared to competition. And I *think* I saw some nice pictures at high ISO from the 5DIII, but may be wrong there.

What am I missing?

Let's simplify the world down to a single pixel sensor. It has a very simple API (this being modestly simplified, but not by much):

interface Pixel {
void SetZero();
uint16 GetValue();
}

If you want to take a picture, you tell the pixel to zero itself, then you open the shutter, wait a while, close the shutter, and finally read out the value of the pixel. You'll note that the pixel has no clue about ISO speeds and whatnot. It's just a little capacitor that builds up charge from photons that arrive.

When you read it out, you get an integer. If too many photons arrived, you'll get MAXINT. If none arrived, you get zero. To keep things simple, let's assume that the sensor is perfectly linear in its response to photons. Double the number of photons, double the integer you get back. (In real life, there's an analog-to-digital converter in there that tries to convert the charge in the capacitor into something resembling linear response. Let's ignore that for now.)

Instead, let's talk about mapping this linear uint16 to color values in a JPEG (which go from 0-255). Every sensor has a "base ISO" of some sort. This indicates that an exposure for that base ISO should get close to MAXINT and a standard 50% grey card should come out to MAXINT>>1 (i.e., half of maximum). The simple answer is to just take the high eight bits and call it a day.

When you're going to a higher ISO value, all you're doing is shifting the 8-bit window of that uint16. The high bits are zero anyway, so ignore them. Every bit you shift is exactly equivalent to doubling the ISO value.

So.... if your pixel gives 16 perfectly absolutely awesome noise-free bits, then you can shift 8 times. If your base ISO was 100, then your final ISO is 100 * 2^8 = ISO 25600. In reality, the low-order bits are noisy, and the lower you go, the less useful information you get. Furthermore, say you only had 14 real bits of information (i.e., the bottom two bits of that uint16 were always zero). You could still shift by 8, and you're still technically shooting at ISO 25600, but you've only got 6 bits of non-zero signal, and the low-order bits of that are going to be noisy crap.

To complicate things modestly, when you have a larger pixel, your base ISO might be higher. The Nikon D700's base ISO is 200, versus 100 on the D800. That means the D700 kinda gets the first shifted bit for free. (Downside: if you're shooting something that's stupidly really bright, you might find yourself wanting a neutral density filter on your lens. For most people, this is a non-issue.)

Whew!

What this boils down to is that many cameras will claim to support ISO 25600 or higher, but they're not exactly doing it very well. That's why DPReview (and others) conduct various tests to measure noise, resolution, and so forth. Many camera vendors will play post-processing games to try to clean up the mess they get from their sensor. You can run all manner of noise reduction algorithms, but to really clean up a mess, you're also going to get rid of very fine details. Or, you can just downsample the image altogether, pooling several adjacent source pixels into one final pixel. You give up image resolution, but you gain back the ability to have a non-crappy high ISO exposure.

If you're hoping to print something 6 feet tall, sharp as a tack, you'll be unsatisfied with this tradeoff. If, however, you're shooting for a newspaper or web site, and you don't need anything more than 1000 pixels across for the final image, you're going to be perfectly happy shrinking things down from the source resolution. (Which is exactly what newspapers and so forth do.)

After all that, I can finally address your question. If you're comparing a hypothetical 22 megapixel vs. 36 megapixel camera, otherwise made with the same generation of sensor technology, the 22 megapixel camera may have less noise in the low bits. The 36 megapixel camera has more pixels. When you reduce the image from both cameras to your target output resolution, they'll probably perform very similarly.

When you want to talk about the specifics of the Canon this vs. the Nikon that, you instead need to look at the test measurements. Those data seem to suggest that the Nikon D800 kicks everybody's ass. Today. We'll see what comes out tomorrow.

Ok, more interesting info, so thank you!
And of course more interesting questions to come (at least for me)
I am on my mobile phone so i'll just ask one which i can't keep for later: so if i understand how the machine works, ISO setting only actually matter for jpeg output? To put it differently, if i could take two identical shots, at the same time, all settings being the same except ISO, will the generated raw files be identical?

The ISO setting affects the voltage that is fed to the amplification circuitry on the sensors. Higher voltage means more sensitivity, but also more noise. Lower voltage means a cleaner image, but longer exposures required.

So, no, not just for JPG images. It also matters for RAW.

-ml

I'm not entirely sure that's correct about the voltage variation. If anything, it will vary from one camera to another.

Certainly, when I've radically underexposed a shot at a low ISO then just cranked it up in Adobe Lightroom, the effects are indistinguishable from just shooting at the proper high ISO to begin with.

I've read up extensively on this stuff in the past, but don't have any current links to provide you. Do a little research, though, and discussion of voltage/amplification/noise should pop up.

I thought I'd read that the amplification was only turned up when you enable those extended ISO modes that most DSLRs have.

But a quick bit of Googling proves I remembered wrong

Changing the ISO settings is basically changing the gain on the amplifier between the sensor and the A-to-D converter.

http://photo.stackexchange.com/questions/2946/how-is-iso-implemented-in-digital-cameras

Yes, I thought I read the opposite some time ago, but I was not particularly interested in the topic at the time and may be remembering wrong. In any case, I thought that the bit-shift Dan mentioned was in fact the "extended" ISO modes, while the ISO setting per se consisted in - that is the way I remembered - changing some "hardware" operating parameter on the sensor itself. Mark's amp voltage change explanation seems to fit well what I remember. Of course, I really don't know. I am mostly learning how this works as we speak.


In either case, I wonder why is Nikon D800 ISO sensitivity is reported 100-6400, while Canon 5DIII is 100-25600 (again, I am just curious to understand how it works, no intention to prove any specific product "better").

If ISO setting is as Mark indicates, one may argue that Sensor+amp circuitry on some cameras be good enough to allow workable pictures at higher ISO, while some other sensors+amp are not.

If ISO setting is only software/firmware based, as Dan suggests, then I can't find a reason why Nikon shouldn't push the settings all the way to 25600, a good marketing tool regardless, right?

Maybe... but not necessarily.

People in the market for a Nikon D800 are likely to be somewhat knowledgeable about digital photography. You [Taym] and I are not world-class experts on the subject, but we both know that anybody claiming to create usable photos at ISO 25600 is exercising extreme marketing hype, and not only that claim but perhaps others they might make become suspect.

Such a claim would instantly bias me against the Canon, and their "marketing tool" (in my case at least) would work against them.

tanstaafl.

Yes, of course you're right, and I was exaggerating in "2.", above.

But actually, precisely because these cameras target somewhat knowledgeable market, I seems unlikely to me that Canon is producing a sensor which is just identical in performances to Nikon's, but at lower resolution and with a mere software tweak used to throw at buyers a "fake" ISO 25600 (and dpreview.com does not put it that way, in fact, for what it is worth). While we know that pictures at 25600 are in many cases useless, I would also reasonably expect that the whole ISO range from 6400 to 25600 does bring benefits, just as higher resolution does. One may argue which is a more relevant benefit, but still.
And, this seems to me a realistic possibility since the ISO setting is actually modifying how the sensor responds (by changing the voltage fed to it) before the ADC kicks in, so before entering the digital domain.


That actually is one of the most advertised features of the 5D Mark III. Or, at least, it is in the form of "best camera ever to take pictures in the dark", or something along those lines. Still a bold statement, I'd say, that I would expect carries at least some truth in it.

This is a 5DIII ISO 12800 shot: http://www.flickr.com/photos/davebass5/8040289680/

It looks great to me. Now, unless I am missing something obvious, this could be taken at a twice as fast shutter speed than one could ever do with a D800 (at 6400). That's a feature, and a competitive advantage, that one may find desirable. Certainly the D800 will allow for other things that the 5DIII won't.

Now I, as a novice, amateur, and one who likes to carry his camera around when travelling and "size the moment", I think the ability to use a faster shutter speed is more valuable than pushing the resolution to 36Mpx. Indeed, others will prefer otherwise.

Apparently, I was wrong about how sensors do high ISO. Interesting.

That said, the DPReview tests and DxO people certainly know what they're talking about, and that's that the D800 has a kick-ass sensor that performs very well at high ISO, particularly if you're willing to shrink things back down again later.

On the other hand, the raw files are almost twice the size of other cameras.

At the end of the day, you buy what fits your budget and solves the problem. If you've got a specific thing that you're shooting a whole lot, then you might make specialized decisions about gear that are better optimized for that use case (e.g., purchasing a really bright prime lens of the size that you might otherwise spend most of your time zoomed). If you lack that sort of specific use case, then this whole discussion sounds a bit like premature optimization. It's not necessary.

Lastly, if you just need something to carry around for spontaneous moments, then you should be paying attention to size and weight as much as the quality of the sensor. You may prefer to skip the D-SLR universe entirely and go for one of these world-beating compact things, like the Sony RX100.

Definitely, but I never intended to find the best sensor out there; I was more interested in understanding how the technology works. Looking at what top producers are doing can give you some interesting hints about that. And, on those lines, I was (am) wondering why they do what they do.

For example, while Nikon seems to have pulled out a higher resolution sensor than Canon that also performs slightly better when cropped down to the same res than Canon's, it seems to me there's also more than that in the whole story, which is interesting. In fact, Nikon sensor does not reach the ISO values that Canon sensor does. In light of what the ISO setting does physically, such extra feature is an interesting fact that seems to suggest that Nikon and Canon are going two different paths, to some extent.

So, I am just observing that

A fun thing I've always enjoyed with my cameras, is their ability to take great photos sans flash in situations where everyone around me is scratching their heads in puzzlement.

A lot of that goes down to the optical image stabilization in the lenses I choose, but a lot more goes to shooting at up to ISO 1600.

A newer body would give me 2-4 stops (ISO) more of exposure latitude there, which given the results I'm already getting, would be astounding! Granted that I'm already happy with what I get at 1600, the difference between 3X versus 4X that are pretty much moot.

So perhaps I ought to upgrade. Just need to find the right camera body that's compatible with my (Canon EOS) lenses. Come-on Canon, gimme a great body with onboard flash (or "speedlight" in Canon terminology)!

I found that image stabilization makes a huge difference for me. In some specific situations, I was blown away.
I took some pictures at a concert in particular, with a 70-300 IS mostly set at 300mm (which we've been talking about here on the BBS a while ago). Instead of the expected blurry mess :), I got some amazing pictures. That is entirely due to the good equipment and IS in particular, because I really did not do anything special, I had no tripod or even monopod, and I was essentially lacking any experience in shooting in those lighting conditions. I just gave it a try. Those pics were so successful among friends I ended up putting them on Flickr for them to download!

And so I did. I now have a Canon 7D body, supplanting the 40D.

It's a nice camera, very quick, lots of nice features including real weather seals, etc.. But despite having native ISO 6400, plus an "H" mode of 12800, it isn't really that much better for noise than the 40D was (native 1600, "H" of 3200).

The 7D here seems to be somewhere between 1 - 1.5 stops better than the 40D, though the built-in noise reduction firmware makes it hard to tell.

However.. since it has about double the number of pixels (18mp versus 10mp for the 40D), I suspect I can just save my images as half-sized "mRAW (10mp)" and see an extra stop or so of usable ISO from pixel binning. Not tested yet, but hopefully so. I've always been happy with 10mp, so no hardship here in continuing at that file resolution. And doing so keeps the storage/computing requirements more or less unchanged.

I'm enjoying the new camera, but also the second toy:

A new zoom lens in the bag: the Sigma 18-250mm f/3.5-6.3 DC Macro OS HSM super-zoom. This lightweight swiss army knife now replaces the Canon EF-S 17-85mm-IS as my primary travel lens.

Image quality looks to be improved (versus the Canon 17-85mm), weight/bulk are down, the image stabilization works very well, and the zoom range is phenomenal. Focus is fast, but cannot be overridden manually (as with the Canon ring type USM lenses) unless the AF/MF slider switch is adjusted first.

So now I can still cart the heavy 7D body along, but with only two lenses in the bag, both rather light in weight: the Sigma, plus the Canon EF-S 10-22mm for indoor shooting. All without cutting off circulation as I shoulder the kit bag.

Happy days!

Merry Christmas to you!

I loved my 7D, great choice Mark.

And I spoke in the past tens because I have my little story to tell you guys too: in few days I sold my 7D+10.22mm and got a 6D, with just 200 Euro extra.
That's the surprising (to me) power of "annunci.ebay.it" which, I now realize, half of the country is watching day and night.
annunci.ebay.it is a Craiglist type of service eBay.it has here, which I had no idea could be so popular. As I've been thinking of a full frame camera for a while, I decided one night (around midnight!) to post my 7D and the only EF-S lens I have (10/22mm) ads, without thinking too much - after all I was very happy with my 7D.
The morning after, I had tens (!!) of emails from all over Italy for both pieces. Wow!

So, in the end I thought: why not? It's Christmas after all and that will be my present to myself, I guess. In two days the entire operation was done and I am now the very happy owner of a Canon EOS 6D!


Now I am in the market, in the long term, for either a 17-40mm or a 16-35mm to replace my old 10-22mm.

You'd not have have any luck trying to pry my beloved 16-35L from my cold dead hands.. Even on cropped format it's a great focal length and a fantastic lens! Decent size too (not massive like many L lenses).



Happy Holidays!

Time to amend that thought: Having now seen some of the images (at reduced size) on my 1920x1200 IPS notebook screen, I'd say the 7D is giving me at least 2 stops extra for usable ISO, over the 40D. Which is pretty good considering the 40D was widely thought to be less noisy than the 50D, and the 7D is reported to be only slightly better for noise than the 50D.

Maybe it's the built-in noise reduction, maybe just the binning of pixels when images are reduced for display.. dunno, but the ISO 3200 / 6400 shots look fantastic!

Cheers

So, one more very positive opinion on the 16-35 I've been looking for some used ones. Do you own version I or II, Mark?


We're now going to my parent's house in the mountains. I should have sorted out all issues with internet access from there (there's an ISP that offers radio-based connectivity, which I think I mentioned here last August), but you never can tell until you're on site. I will finally test my 6D on the field, which I can't wait.

If I can't read you all, Happy 2013!

I believe mine is the original 16-35L, from about 10 years ago. No "II" anywhere on it. A very, VERY sweet lens!

Some used version IIs are sold at 850-950 Euros here. Iam guessing a cheaper version I could be a deal.
V. II is slightly bigger in size, and has various IQ improvements, based on some reviews I read. A brief review with some good pictures to compare the two versions, here.

Mmm.. The II version would have to be a lot better than the original for me to want that extra bulk in the bag. For me, the original 16-35L is stunning for the quality and the small size of the lens.

I'm sure either will be excellent for you though!

Speaking of which.. I think I'm going to sell my 70-200L-IS f2.8 lens -- it simply doesn't get used enough, despite the incredible image quality from it.

It is likely heading to eBay unless somebody I know wants it.

And ditto for the 70-300-DO-IS compact zoom. My new Sigma ultra-zoom has displaced it as well as the 17-85mm-IS Canon lens.

Cheers