Messages

16

Lenses / Re: Main difference between 70-200 f/2.8 IS I and II, Non IS, and f/4 IS

« on: April 25, 2013, 07:18:06 AM »

I have owned the 70-200/2.8 IS mk I, and currently own the mk II version. Used at f2.8 (which you'll probably rely on a lot to get the shutter speeds needed), the difference is dramatic. As bad as the mk I is at f2.8, it is acceptable if stopped down to f4 - which begs the question, why not just get the f4 IS instead of the mk I? If used in auto or Tv, it can't open up to soft apertures, plus it's cheaper, lighter, has better IS (4 stops vs 3), and is sharper at all equivalent settings. 

While IS isn't necessarily useful for action shots due to the high shutter speeds, it can come in handy for composing. Plus the moment you use the lens for slower moving subjects, or do video, IS will come in really handy.

Even though it's no match for the mk II, the non weather sealed 2.8 non IS is sharper than the mk I 2.8 IS lens.

As video is high up your list, I'd recommend stretching to the 2.8 IS II, and if you really can't afford it, the only other suitable option in my opinion is the f4 IS. If video wasn't so important, questionably the f2.8 non IS instead.

17

Lenses / Re: Rubber Seal 24-70 f2.8 L

« on: April 24, 2013, 02:07:31 PM »

Concern is what. To do with the other places the water can come in. It took my 85L out in the rain once and it rained right through the focus distance window, the mount was dry between camera and back if the lens.

That's the exact problem with stuff like the dust donut - it can only attempt to fix the leak at the lens/body join and does nothing to seal up the rest of the holes in the lens. However, the 24-70 mk I is a weather sealed lens, so all those other potential water ingress points should be covered. Presuming yours only has damage to the rubber gasket at the lens mount, it should work - but as to whether its anywhere near as good as the genuine $211 Canon seal, I couldn't say. And I guess there will be a bit of a wait seeing as it's still at the kickstarter stage.

18

Lenses / Re: Rubber Seal 24-70 f2.8 L

« on: April 24, 2013, 01:01:19 PM »

Is this one of those rare occasions where a dust donut makes sense?

http://www.kickstarter.com/projects/77243737/dust-donuttm-add-a-weather-seal-to-the-mount-of-an

19

Third Party Manufacturers / Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C

« on: April 22, 2013, 02:13:35 PM »

I know I said I'm done, but just one quick last post from me on the subject. DPReview have a hands on preview of this lens up on their website, and on the first page they wrote this:

Sigma's choice of F1.8 as maximum aperture isn't a coincidence; it means that the lens will offer the same control over depth of field as an F2.8 zoom does on full frame. What's more, it will also offer effectively the same light-gathering capability as an F2.8 lens on full frame. By this we mean that it will be able to project an image that's just over twice as bright onto a sensor that's slightly less than half the area, meaning the same total amount of light is used to capture the image. This is important as it's a major determinant of image quality. Essentially it means that APS-C shooters will be able to use lower ISOs when shooting wide open in low light and get similar levels of image noise, substantially negating one of the key advantages of switching to full frame.

http://www.dpreview.com/previews/sigma-18-35-1-8

20

Third Party Manufacturers / Re: 135mm f/1.8 DG OS ART Next from Sigma? [CR1]

« on: April 21, 2013, 09:16:25 AM »

Any hint of HSM? Could be something for indoor sports, too. Unless the Art-range keeps converging to L-prices… (for me, at least)

I'd have thought so. All of the high end Sigma glass has HSM.

f1.8 and OS, coupled with Sigma's recent proven performance of the 35/1.4 - if it is real, this could turn out to be an astonishing lens.

21

Lenses / Re: Lens Choice

« on: April 21, 2013, 09:13:06 AM »

Which Canon 70-200 are you thinking of? Obviously that Sigma 70-200 OS is gunning for the Canon 70-200/2.8 IS II with its similar specs, but other than beating it well and truly on price, it can't begin to get close to the Canon when it comes to real life performance.

As for something from Canon that's nearer to a sensible price, the three other Canon 70-200's (2.8 non IS, and the two f4 versions) are all great options. Out of the three, I'd actually recommend the f4 IS. On paper its specs aren't up to the Sigma (its a whole stop slower), but its weather sealed (unlike the non IS Canon 70-200's and the Sigma), has 4 stop IS, its light weight, and its performance is beyond what the raw specs suggest.

Canon 70-200/4 IS vs Sigma, both at f4:

http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=806&Camera=453&Sample=0&FLI=4&API=2&LensComp=404&CameraComp=453&SampleComp=0&FLIComp=4&APIComp=0

Or if you want to compare the f2.8 non IS to the Sigma, try this:

http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=806&Camera=453&Sample=0&FLI=4&API=0&LensComp=242&CameraComp=453&SampleComp=0&FLIComp=4&APIComp=0

22

Third Party Manufacturers / Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C

« on: April 20, 2013, 08:01:49 PM »

Yes, I'm still standing by all of it. They're all different ways of putting across the exact same point. You quite clearly don't get it, so I'm out. Keep arguing this all you like, I'm done.

23

Third Party Manufacturers / Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C

« on: April 20, 2013, 06:35:07 PM »

OK, now I know you're trolling. You failed to quote the part of my post that answers this:

The reasons why FF sensors typically produce less noisy images in practice than APS-C sensors are that a) the (usually) bigger individual pixels produce a better signal-to-noise ratio, and b) the native image requires less enlargement when printing.

So you agree that a larger enlargement makes noise more visible? If so, it seems like we're agreeing on this, but arguing about semantics.

From my point of view, amplification and magnification amount to one and the same thing. Take two different sized sensors with the same number of MP (1D X and 7D for example), then the smaller sensor clearly has smaller pixels. Each pixel receives less light, so in order to give the same electrical signal to create a calibrated ISO 100, it has to amplify to a greater level the smaller signal created from the smaller number of photons collected at its smaller pixel. However, take two sensors of different size with pixels of the same density (eg 1Ds mk III and 30D, or D800 and D7000), and on a pixel level, each pixel is the same size, so it collects the same number of photons, creates the same strength electrical signal and requires the same amount of amplification. But it is magnified less from that larger sensor (each pixel, together with its noise is a less significant part of the whole image), so it's noise has a lower effect on the whole image. Not all FF and crop comparisons fall into one of these two convenient categories, so it's usually a combination of amplification and magnification differences between the two. But one thing is for sure - take the whole image, and the bigger sensor will be less noisy. And all things being equal (same generation technology etc), you'll find the noise ratio is directly in line with the area ratio.

Similarly speaking, a 1.6x crop of FF is no different from a 1.6x crop sensor. The exposure doesn't differ with different sized sensors. The noise does. Bigger area to capture light equals more light captured. That equals lower noise. Or you can turn it around by bumping up the ISO and create the same noise with greater sensitivity. That is what makes an f2.8 lens on FF equal to an f1.75 lens on 1.6x crop.

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Third Party Manufacturers / Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C

« on: April 20, 2013, 05:05:51 PM »

There is some truth in this part of your statement but it has nothing whatsoever to do with the dimensions of the sensor.

So you're saying pretty much all FF sensors are better than pretty much all crop sensors because of something other than their bigger size? I'm confused by your logic now

Bingo!

If I use masking tape around the edges of my full size sensor to leave only an APS-C sized area, what does it do to the quality of the image on the exposed area? Nothing. What does it do to the exposure value? Nothing.

Print a whole FF image at 1m wide, the noise hides quite well. Now take a crop of that same image and print that crop at 1m wide, do you think the noise will be no less apparent?

You'd need to shoot the cropped image at a lower ISO to show an equivalent amount of noise in the final print.

25

Third Party Manufacturers / Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C

« on: April 20, 2013, 02:46:46 PM »

There is some truth in this part of your statement but it has nothing whatsoever to do with the dimensions of the sensor.

So you're saying pretty much all FF sensors are better than pretty much all crop sensors because of something other than their bigger size? I'm confused by your logic now

ps - it seems like you're slowing coming around to understanding my argument. Using that metabones analogy, you got the bit about how both the combined effect of aperture and image circle is equal to the total amount of light coming through the system. You now seem to get the other end of the argument - FF allows you to work at higher ISO's than crop. If you could just accept this missing part of the puzzle about it being the larger size of the sensor which allows you to work at these higher ISO's, I think you'll have it. Or are you going to start arguing about some other random part of the rationale?

26

Third Party Manufacturers / Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C

« on: April 20, 2013, 01:58:46 PM »

Why do you care how much light the lenses capture? That's irrelevant. What I care about is the final exposure.

Because the Sigma is an f/1.8 lens, it may be quite possible that the 24-70 does not create a bright enough exposure for a photographer in a low-light situation, so the Sigma will be much "nicer" to use in that situation.

What about using the FF system at a higher ISO? As the FF sensors larger area allows it to capture 2.56x more light, you can use an ISO 2.56x higher (just over a stop), without suffering from any more noise than the crop sensor. ISO 10,000 on a typical APS-C sensor gives the same noise as ISO 25,600 on a typical FF. If you do choose to make use of the higher ISO's made available to you, the final exposure is the same, and the f1.8 crop system offers no low light advantage over an f2.8 full frame system.

27

Third Party Manufacturers / Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C

« on: April 20, 2013, 10:30:04 AM »

This is a compound error from the previous incorrect statement. Sensor size is not a factor in this.

My original argument which has been hotly debated was merely that as nice as this Sigma 18-35/1.8 is on a crop camera, it's not quite as nice* as a 24-70/2.8 II is on a full frame camera.  I was comparing two complete systems, sensor and all. I know that a 24-70/2.8 is no match for this Sigma when they're both mounted on a crop body.

*by nice, I mean the 24-70 on FF goes wider, longer, is capable of a vaguely narrower DoF and capturing vaguely more light.

My argument is simply the total quantity of light a system can capture is more than just aperture - it is a combination of aperture and sensor size. The entrance pupil size when both systems have an equivalent FoV is a simple way of quantifying that.

But if you disagree with me and think that an f1.8 lens on 1.6x crop captures more light than a lens with an equal field of view at f2.8 on full frame, then fair enough. I've tried explaining this concept in many different ways, and you still don't get it. So I give up.

28

Third Party Manufacturers / Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C

« on: April 20, 2013, 08:20:57 AM »

I've decided to offer some help to Sigma with an FAQ set for potentially confused customers.

+1

Think of the metabones speed booster. Imagine now that they created one which made a FF lens create an imaging circle to match the APS-C crop sensor found in a Canon camera - a 1.6x telecompressor. That way you could mount, say, a 24-70/2.8 on crop with the metabones adapter, and get an identical FoV that the lens achieves on FF.

The 24-70/2.8 would be turned into a 15-44/1.75, right?

Now, we all know f1.75 is faster than f2.8. No-one is disputing that. If you mount this lens on the crop sensor camera with the telecompressor, it will allow for more than a stop faster shutter speeds at equal ISO's. It is an f1.75 lens, and no-one can argue with that. But where does this metabones get this extra speed from? Its not magic - its just it compresses the larger image circle into a smaller one - that extra light from that larger FF image circle is now condensed down into a smaller, more intense imaging circle, and is then received by a smaller sensor. However, in total its only the same amount of light/photons coming in through the lens which hits the sensor. The FF sensor and the APS-C sensor with a telecompressor both receive an identical number of photons, but the APS-C sensor has brighter light presented to it - more light per area - in other words its just over a stop brighter.

ISO's are rated to make exposure calculations work. What one camera does to achieve ISO 1600 isn't the same as another camera at ISO 1600 - especially with different size formats. The larger sensor as a whole has more photons hitting it at a particular aperture, so it needs to amplify the resulting electrical signal less for any given ISO. And even some cameras with the same sensor have to do different amplification, such as the Sony NEX 7 and Sony SLT A77.

If you can't see that, haven't you ever wondered why FF sensors are typically just over a stop better than crop sensors when it comes to noise? This faster aperture of the Sigma simply allows the noisier sensor to work at lower ISO's to finally fight back. Use a 18-35/1.8 at 35mm f1.8 1/100th of a sec ISO 10000 on crop, or a 24-70/2.8 at 56mm f2.8 1/100th, ISO 25600 on FF and you'll find its the same framing, depth of field, exposure and noise. (well, it would be if the Sigma was slightly brighter at f1.75)

Regardless of how you understand this difference between full frame and crop, and either agree or disagree with me, this Sigma lens really ups the game for crop users. From the specs point of view (and samples images), it looks great.

29

EOS Bodies / Re: 21mp Sensor in the 7D Mark II? [CR1]

« on: April 19, 2013, 06:01:44 PM »

I hope for the best about 7D2: new dual DIGIC 6 and new CMOS (NEW Technolgy, NOT the same CMOS as on 1DX, 5D3 edition customized for 7D2).


10x!

No need to be "furious with Canon".  And where did you read a rumor that the 7D2 would get "dual digic 6"?  I must have missed that.  Seems very unlikely to me, unless the price is more in the $3k+ range.  Which would be absurd...a 1.6x crop sensor is a silly compromise in the first place (at least now in 2013).  To attempt to sell one at such a high price, would be a disaster.  1.6x crop, is so very 2002...it's time to move on to something else, something bigger.  I mean, if "reach" is all they care about, they might as well go smaller and make a micro 4/3 size, 3:2 sensor for the 7D2.  But they won't.

you have not a clue what you are talking about, as long the pixel density is higher in a APS than a 24x36 there are many people who has advantage of the smaller sensor, bird photographer, etc

TC?

30

Third Party Manufacturers / Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C

« on: April 19, 2013, 11:29:32 AM »

You can compare what you want, as long as you it correctly. The way you do it is the way you can compare angles of view. This is fine as long as you don't make the mistake to consider angle of view = focal length and to put this value into a f/stop calculation.

Angle of view is a combination of focal length and sensor size. If we're talking about two different sized sensors, to get the same angle of view, we have to adjust the focal length to suit.

Focal length is what it is. You can mount an old Zeiss for Hasselblad lens on your Canon camera and the focal length will not change. It would give you the same framing of a 100mm Canon lens.

You're looking at it the wrong way here - while the 100mm Zeiss frames the same as the 100mm Canon on the Canon SLR, it frames very different from how it would on the Hasselbald. On the Canon, you've cropped out a fair old proportion of the image circle, resulting in much of the light being cropped out and a narrower FoV.

More flow, but not more pressure. Same with light: you get more light coming in in total, but the amount of light / surface of the sensor would be the same. Any extra light that comes in will not affect exposure.

That's my exact point - the intensity of the light at any area of the sensor isn't greater, its just there's a bigger area of it, so in total more light is captured by the system.

Same as above. A smaller sensor is actually a smaller mouth to feed. This is why you can have compact cameras with 1" sensor and f/1.8 lenses.

Again, it looks like you've nearly got it here - it does need that faster aperture to make it equivalent.