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Messages - epsiloneri

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Lenses / Re: EF 24-70 f/2.8L Replacement [CR2]
« on: October 12, 2010, 06:41:37 PM »
While the effective field of view on a crop camera may be the same as a longer lens on a 35mm, the focal length does not change and therefore neither does the aperture.  A 17 - 55mm lens may give the same FOV as a 27 -88mm but it's still a 17 - 55mm and the relationship between the first element and the focal length remains unchanged as does the aperture.

You're right, but what is your point? The focal length just gives the image scale. 50mm/2.8 on FF gives exactly the same field (solid angle) as 80mm/4.5 on 1.6x APS-C (barring lens distortion). The flux of incoming photons per solid angle will be the same. The DOF will be the same. If the detectors have the same number of pixels with the same sensitivity (say fraction of photons actually detected, also called quantum efficiency) and read-out noise, dark current etc, then the resulting image will be statistically identical in all respects.

The lens is just an optical system to capture photons and compress them to a small image. The advantage of FF sensors is not that they are inherently more sensitive. The advantage is that it's easier to make optics that produce larger image scales (e.g., it's easier to produce a good EF 80mm/1.2 lens than an EF-S 50mm/0.75 lens).

Lenses / Re: EF 24-70 f/2.8L Replacement [CR2]
« on: October 12, 2010, 06:09:31 PM »
So, bottom line, if you are waiting for a 24-70mm f/2.8L IS because you want a FF-equivalent of your 17-55mm IS, you can have that right now as the 24-105mm f/4L IS.

You're right, and that was exactly my point :) Jason was complaining that his 24-105/4L wasn't as good on his 5D2 as his 17-55/2.8 had been on his 50D, and I was surprised, because I thought the 24-105/4L would be similar but slightly better, if anything. I then went on and tested a 17-55/2.8  on a 7D and a  24-105/4L on a 5D2, and found that the latter was indeed very similar, but slightly better performer (for my copies).

But the bottom line is that I do not find slightly better compelling enough to go FF. A good 24-70mm f/2.8L IS on the other hand would convert me in an instant.

Lenses / Re: EF 24-70 f/2.8L Replacement [CR2]
« on: October 11, 2010, 07:24:42 PM »
Just FYI Justin, I got access to exactly your setup (5D2+24-105/4L) and took the opportunity to compare it to my 7D+17-55/2.8. Tripod, no IS, with a boring bookshelf as the subject. Manual focusing of centre with live view, remote shutter release with mirror lock up. Focal plane parallel to bookshelf. 24-105/4L @ 70mm (supposedly its worst focal length), 17-55/2.8 @ 44mm (the equivalent). iso 160 and 1s exposure for 5D2, iso 100 and 1s exposure for 7D (gives the same exposure level).

Result: Sharpness about equal in corners, 24-105/4L better in centre.

Then I stepped down the aperture 2 steps (i.e. to 8.0 and 5.6, respectively) and increased exposure time to 4s.

Result: 24-105/4L@8.0 improved corners significantly, and center somewhat, clearly out-resolving the 17-55/2.8@5.6, which didn't improve as much compared to wide open.

Conclusion: The resolution of the 5D2+24-105/4L is no worse than 7D+17-55/2.8, so have no remorse for selling your EF-S lens.

(NB, I can't guarantee that my results are typical, maybe I received a good 24-105/4L copy and a poor 17-55/2.8, but what I find is in line with expectations from MTF measurements)

If you're interested I can find a way to post relevant crops of the images.

Lenses / Re: EF 24-70 f/2.8L Replacement [CR2]
« on: October 05, 2010, 05:06:33 PM »
In terms of sharpness, I have to stop down to f11 on the 24-105 at 70mm to get even close to the 17-55 at the long end.

That is surprising, I haven't seen complaints on the sharpness of the 24-105/4L IS before (most complaints are about the strong barrel distortion at 24mm). Perhaps you have a bad copy/AF problems? According to MTF measurements by photozone.de, the 24-105/4L on 5D2 should be slightly sharper than 17-55/2.8 on 50D (although the latter is better than 24-105/4L on 50D; this is because of the APS-C 1.6x center resolution disadvantage compared to FF). It also seems the 24-105/4L is at its worst in the corners at 70mm (but still better than 17-55/2.8 at 55mm).

But yes, I'm very fond of my 17-55/2.8 IS lens and, just as you, I'm waiting for a normal F/2.8 zoom with IS to switch to FF (e.g., 24-70/2.8L IS). Even with a good calibrated copy, merely doing "slightly better" is not big enough incentive for me to switch.

Lenses / Re: EF 24-70 f/2.8L Replacement [CR2]
« on: October 04, 2010, 08:15:06 PM »
I sold my aps-c camera for a 5D2 almost a year ago and had to sell my 17-55 2.8 IS, my favorite lens.

The 17-55/2.8 IS lens on APS-C @ iso 100 corresponds to 27-88/4.5 on FF @ iso 160 (same exposure, same depth of field, same photon noise), so if you were content with that lens I see no reason you would be less happy with 24-105/4L IS on 5d2.

Canon General / Re: Canon Develops World's Largest CMOS Sensor
« on: September 03, 2010, 01:02:14 AM »
BTW, here's another shot of them side by side

Crazy big! Thanks for the pic. Hope you're having fun at the expo.

Canon General / Re: Canon Develops World's Largest CMOS Sensor
« on: September 02, 2010, 01:23:33 AM »
Actually, lenses from 8x10 view cameras would work quite nicely on that.  They aren't as huge as you might think...of course, they aren't point and shoot lenses either  ::)

Interesting. It seems to me that sensors get cheaper faster than lenses, so I predict that we at some point will see inexpensive medium format camera systems that produce the same or better IQ as much more expensive FF/APS systems, with their only drawback that they are bulkier  ;)

Canon General / Re: Canon Develops World's Largest CMOS Sensor
« on: September 02, 2010, 01:11:47 AM »
Hm, let me make a guess... Should that be 640,000 maybe? (6400 * 100)  ::)
It doesn't work that way. The previous post is correct.

Of course it works that way. Both are correct. And btw, log2(100) = 6.639 stops. But note that this doesn't make the large sensor more sensitive (as in more signal per photon).

Canon General / Re: Canon Develops World's Largest CMOS Sensor
« on: August 31, 2010, 05:11:18 PM »
You would need a monster lens to supply that sensor with a big enough image circle. Sounds perfect for wide-field telescopes, but I'm curious what other applications. Probably just a technical demonstration with no plans to put it into production.

I find it annoying, though, that they keep perpetuating the myth that larger sensors are more light sensitive, when it's (almost) all in the aperture of the optics. Larger sensors merely samples a larger field of view.

Lenses / Re: Canon Announces 8-15 f/4L Fisheye Zoom
« on: August 26, 2010, 08:18:33 AM »
From time to time, it makes sense to really read postings... ;)

Ups! Yeah. Thanks.

EOS Bodies / Re: Canon Announces EOS 60D
« on: August 26, 2010, 06:45:20 AM »
I'd be mostly interested in if they've been able to get rid of that awful banding visible in high-ISO shots with the 50D and 5D mkII. They've fixed it in the 7D, which was the major reason I upgraded up to it from the 50D. I'm very happy with the 7D sensor, very well behaved compared to the 50D. For the same reason I'm not going FF until 5D mkIII, where I hope they'll also have fixed the banding and AF issues.

Lenses / Re: Canon Announces 1.4x III & 2.0x III
« on: August 26, 2010, 06:34:39 AM »
I'd also be interested to see a side-by-side comparison with the mkII's, to see if there is an IQ improvement, in particular for the 2x which is a bit suspect right now. I'm not sure the problem with the 2x mkII is that it actually degrades the IQ or just makes already present lens imperfections more apparent. It would make sense therefore to test with a well-corrected lens, say the new EF 300/2.8L IS II (which must be really exceptional if it's better than the already exceptional mkI).

Lenses / Re: Canon Announces 8-15 f/4L Fisheye Zoom
« on: August 26, 2010, 06:15:56 AM »
I wonder if this will replace the EF 15/2.8 fisheye. It's of an old design, but the optics are excellent and the 2.8 makes it better suited for low-light photography (e.g. aurorae). The non-USM focus motor is loud, but AF is not much of an issue on a fisheye (in fact almost unnecessary - MF works very well).

Lenses / Re: Canon Announces 8-15 f/4L Fisheye Zoom
« on: August 26, 2010, 06:09:23 AM »
Gut feeling says it's going to be one of those lenses that refuses to take filters and hoods....

Just out of curiosity... what kind of filter would be of interest to use with this lens? The only useful filter I know of for digital photography (outside clear "lens protectors") is a polarisation filter, but this lens would be far too wide for that to be sensible. Are there any other cool useful filters I've missed? Or are you perhaps considering using this lens for chemical photography?

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