Messages

31

Lenses / Re: Better for head shots, portraits: 100mm f.2.8L Macro IS or 70-200 f.2.8L IS II?

« on: April 18, 2013, 05:38:54 PM »

I have them both, and there's really nothing in it at normal focusing distances. If only 100mm will do or I need to get very close, I'll take the lighter lens. They're both equally spectacular for portraits at 100mm, but I personally prefer to change focal length a bit to go allow me to take both tight head portraits and upper body group shots without having to change perspective too much - so invariably I find myself using the zoom.

32

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

« on: April 18, 2013, 04:58:17 PM »

This is great for crop shooters.  However, before everyone gets excited over the f/1.8 bit, you have to remember that f/1.8 on a crop sensor is nothing like f/1.8 on a FF sensor.  This lens will give the same angle of view, image noise for given exposure parameters (*1), depth of field at a given AOV and subject distance (*2), etc. etc. etc. as a 28-50mm f/2.8 full frame lens.

In other words, if the lenses and sensors are perfect, this lens on a crop sensor would give identical results to a 28-50mm f/2.8 on a FF sensor. 

You mean identical DOF. f1.8 will still give more light on APS-C than f/2.8 on full frame.

No. A FF sensor behind an f2.8 FF lens gathers 2.56x as much light as an f2.8 lens does on a 1.6x crop sensor due to the sensors 2.56x bigger surface area. If you only capture a fraction of all that FF f2.8 light by cropping it, well, the obvious happens from the light gathering point of view. The reason why using an f1.8 lens wide open on crop gives a brighter image than f2.8 on FF (when both are at the same ISO and shutter speed) is the amplification of the crop cameras sensor is 2.56x greater, at the expense of noise at any given ISO rating. In other words ISO 10,000 on crop is pretty much equal to ISO 25,600 on FF in terms of noise. So feel free to shoot smaller apertures on FF and use higher ISO's to get the same light gathering and noise.

The different amplification levels is a bit like how the Sony NEX 7 and the Sony SLT A77 both share an identical sensor, and give the same exposure with the same shutter speed, aperture and ISO, yet the SLT camera has a semi translucent mirror permanently in front of the sensor, acting like a neutral density filter you can't get rid of. Sony just cranked up the amplifier on the A77 a bit more to make it all seem good - at the expense of noise.

So f1.8 on a 1.6x crop is equivalent to f2.88 on FF in terms of both depth of field and light gathering.

I see this Sigma lens as being a crop alternative to the 24-70 II on FF in just the same way as the 17-55 IS is a crop alternative to the 24-105L on FF. Not quite as fast an effective aperture, and not as wide or as long effective focal lengths. Slightly worse on all fronts when compared to the FF equivalent, but none the less a nice string in the bow for crop sensor users. Lets hope it performs well optically, and I like the idea of an internal zoom on a lens covering the normal range, even if the zoom ring rotates the wrong way

33

Lenses / Re: Speedy Manual Focusing?

« on: April 18, 2013, 11:49:37 AM »

The EG-S is great and I leave it in my 5DMkII all the time. Viewfinder brightness is comparable to that of the 7D and I don't ever find the viewfinder to be too dark. IMHO these FF camera's should come with the EG-S as standard.

How does the EG-S screen work exactly?  I'm only familiar with the split prism manual focus screen.

Is the EG-S difficult to install?

Thanks!

The normal EG-A screen has micro lenses that are aimed at the center of the frame to produce a bright viewfinder (but also too much DOF), the precision matte is more like ground glass and much more diffuse. I can't quite explain how it works optically, but when you look through the screen it is much easier to see what is in focus and what isn't. The EG-S effectively shows a shallower DOF.

This site ( http://www.focusingscreen.com/work/5d2en.htm ) shows how to change focus screens, I would recommend a Canon EG-S over a third party one as a third party screen may interfere with the metering accuracy of your camera (notice that you need to change a setting in the camera to account for the different screen in use).

The brightness will really drop off with slower lenses. If you have an f5.6 or f8 lens (or stop your lens down to that and use the depth of field preview button), the EG-S screen will be a lot darker than a normal focus screen.

The rougher, or more matte the focus screen is (such as an EG-S focus screen) the more it can pick up on the off-angle light rays, such as you'd get with the converging light rays from a wide aperture lens. If a focus screen is smoother, such as the stock screen, the artificial 'ground surface' of the plastic screen doesn't have sufficient depth or angles on it to pick up on such off-angle light. The bulk of the light it receives is the stuff close to perpendicular to the focus screen - which explains both why these stock screens don't get as dark when stopped down, and why they can't render the out of focus parts of the image as blurred as the sensor can. Somewhere around f4 to f2.8 is where a stock focus screen fails to show how narrow the DoF is. If you use an f1.2 lens wide open with a standard focus screen, the viewfinder will be very different to the final image.

In response to the original question, focus screens such as the matte EG-S or stock EG-A give the manual focusing user the equivalent info (albiet scaled down) of what contrast detect AF has - no indication of exactly how much it's out by, or any real info about which way it's out. Plus without resorting to magnified live view, you can't accurately see if its 100% there, even with an EG-S screen. But you can hunt around, finding where it looks sharpest and opt for the middle of that acceptable range, hoping for the best if you're only using the non magnified viewfinder. However, a split image focus screen is much like a single point phase detect AF system - the amount and direction of focusing needed to get it spot on are represented by how far out of alignment and which way out of alignment the two parts of the split image are. With not much practice, accurate and fast manual focusing us possible with a split image focus screen.

34

Lenses / Re: Why aren't zoom lenses faster than 2.8?

« on: April 18, 2013, 08:13:08 AM »

There are now:
http://www.dpreview.com/news/2013/04/18/Sigma-announces-worlds-first-F1-8-constant-aperture-zoom-lens

Equivalent of f2.7 FF on a Nikon 1.5x crop, or f2.9 FF on a Canon 1.6x crop. So on Nikon it is faster than an equivalent of f2.8 FF, but not by much. I'd still prefer a Canon 24-70 II on FF, even if it is 'only' f2.8

35

Lenses / Re: 2 filters jammed together

« on: April 12, 2013, 03:48:44 AM »

A rubber band stretched around a filter makes it much more grippy. Hopefully there's enough width for a rubber band on the half of the CPL which is tightened onto the UV filter.

36

Lenses / Re: Why can a Sigma 10-20mm fit on a "FF" Body?

« on: April 05, 2013, 04:42:01 AM »

While some manufacturers such as Sigma make lenses designed for Canon crop bodies, only Canon make EF-S mount lenses. This means these third party EF crop lenses can physically mount on FF bodies, even though the image circle isn't specifically designed to cover such a large area. Hopefully they have enough mirror clearance too.

Does the Sigma 10-20 image circle cover the entire frame when zoomed in to say 15/16mm or longer?

37

Third Party Manufacturers / Re: Dynamic range, high lights information D800 vs 5dmk2

« on: April 03, 2013, 04:49:52 PM »

Can someone give him a helpful nudge? I think his record is stuck...

38

EOS Bodies / Re: 6,5 fps with 40D

« on: April 03, 2013, 04:32:57 PM »

My 40D is certainly the same speed with or without the grip and its extra battery. The only improvements the grip gives me are handling and battery life.

39

Lenses / Re: New 100-400 to Launch with EOS 7D Mark II [CR2]

« on: March 27, 2013, 09:21:45 AM »

100-400 F4 without 1.4 extender, Would be a good alternative to the 200-400 maybe half the cost?

Same constant aperture, and a 4x zoom range instead of 2x for half the cost? A built in TC doesn't account for that much of the cost!

A replacement 100-400 will not be f4 at the long end, unless its bigger and more expensive than the still missing 200-400. There's a need for a lens the size/weight/price/focal length range of the existing 100-400. That means any replacement will be f5.6 at the long end.

(The price will be about double the existing model  )

40

Canon General / Re: Monopod VS IS (Image stabilization)

« on: March 27, 2013, 02:11:35 AM »

It depends on what you're shooting, and how much you want to carry around. For instance, at weddings it's much easier to blend into the background when your second body with the 70-200 mounted doesn't have a big pole poking out of it. And as for stabilisation, I quite often cover water sports events from small motorboats. It's amazing how effective IS can be on the 70-200 II in the choppy water. For my usage, IS is perfect for me on my 70-200, and a monopod could never be a substitute.

41

Lenses / Re: naked eye equivalent?

« on: March 23, 2013, 06:15:50 PM »

50mm focal length is 50mm focal length as long as the lens matches the mount on your camera; Your EF 50mm f/1.8 on a Rebel will look like about 80mm because the Rebel has a smaller sensor.  If you have an 18-55 you could set it to 50mm and compare it to the results from your 50mm f/1.4.

To get the FoV that a 50mm gives on FF, use an EF-S 18-55 at 31mm. An 18-55 @50 gives an identical FoV as a 50/1.4 if they're both on a crop body.

In terms of primes, somewhere in the region of 28-35mm is close to that 31mm to give equivalent FoV of a 50mm on FF.

However, the human field of view is said to be nearer to a lens with a focal lens equal to the diagonal of the sensor - 50mm lenses are cheap and easy to manufacture, and very close to this length, hence their popularity - but 43mm on FF is the nearest match to the human eye. Which makes something close to 27mm lens on crop ideal.

42

Lenses / Re: Buy EF-S 55-250mm f/4-5.6 IS II now or wait until September?

« on: March 19, 2013, 06:47:48 AM »

Now, I see that the petal hood is bigger. Bigger is better? Not for cameras? The difference between the two is small. Unless you have your own opinion, which I want to hear. Convince me the regular one is better when the petal one is bigger and at the shortest sides is a few millimeters bigger.

Even if you don't want to take a video of it, for your own understanding, please just fit the petal hood, make sure the lens is set to autofocus, and then half press the shutter to let the lens AF on different subjects. Try it without looking through the viewfinder, but looking at the camera - just as the people you're trying to impress will see it. If you find the rotation of the petal lens hood impressive, I'm pleased for you.

Please note that the videos you posted were not only through the lens, but there was no focusing there - just zooming.

And as for the depth of the hood, it should be as deep as possible without introducing vignetting. Canon are pretty clued up when it comes to optics - I'd guess they're a bit better at it than you and people that make cheap rubbish to sell on eBay, so personally I'd go with the Canon design.

43

EOS Bodies / Re: Canon EOS 100D Detailed Specs Appear

« on: March 18, 2013, 04:52:13 PM »

The mount is the same for EF and EF-S..... the problem is mirror clearance on the existing EF bodies. The larger mirror required for FF takes more space to swing up than the APS-C sized mirror. If you think outside the box and change the geometry somehow... or even a split mirror!!!... you could overcome that obstacle and fit a FF sensor in. Yes, when using an EF-S lens you would have to crop it to the central 60 percent or so of the image, but it could be done.

SOME EF-S lenses can be used on FF bodies, such as the Sigma 10-20 on a 5D2. It's not an impossible thing, but I doubt Canon is ready for FF compact cameras yet.

Canon EF-S lenses have an extra rubber part that pokes out of the rear of the lens, preventing them from mounting on EF mount bodies. Only cameras with an EF-S mount (crop sensor cameras from the 300D onwards) have the cut out to allow such lenses to physically mount.

Some people have removed it from the 10-22 to use it at longer focal lengths on APS-H bodies: http://www.flickr.com/groups/canondslr/discuss/72157604422834954/

I'm not aware of anyone other than Canon that makes EF-S mount lenses, and such third party crop lenses might have clearance for a full frame mirror, even if the image circle is too small.

44

Lenses / Re: Suggestions for Zoom Lens for Canon Mark 5D Mark iii

« on: March 18, 2013, 12:55:31 PM »

The 70-200/4L will give you better IQ than any of the other options.

+1

And the Tamron 17-50 is for crop cameras

45

Third Party Manufacturers / Re: Which camera brand you actively use, other than Canon?

« on: March 14, 2013, 01:39:37 PM »

iPhone