March 04, 2015, 01:55:39 PM

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Messages - rs

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1
Lenses / Re: Canon ef-s 17-55mm 2.8 is usm GONE
« on: March 03, 2015, 01:19:25 PM »
To Canon, "L" specifically requires that it works with FF.  There will never be an EF-S lens tagged "L".  It can be just as good optically, but it will not get the red ring.

There's one exception I know of - the PowerShot Pro1

2
Lenses / Re: Canon ef-s 17-55mm 2.8 is usm GONE
« on: March 02, 2015, 07:21:34 PM »
This is how I understand it (and feel free to correct me if I'm wrong):

  • For exposure, no difference between F2.8 on crop or on full frame.
  • For depth of field, there is a difference, but only if you maintain the same field of view.

The reason for the difference in depth of field is that to maintain the same field of view between crop and full frame, you have to change your distance from the subject, and that is what changes depth of field.

When you see someone say "F2.8 on a crop sensor is really F4.5 equivalent on full frame," they're talking about the depth of field for equivalent framing only, not exposure.

Teleconverters are another story (and might contribute to the confusion for some), because they DO affect exposure. I believe the reason for this is that it changes focal length (one of the inputs for the aperture value), which changes the ratio, affecting the light that can hit the sensor, and thus, exposure.

Any experts want to chime in to set me straight? :P
The EF-S 17-55/2.8 IS lens is f2.8, and there's no getting away from that. And it also has a focal length range of 17-55. And when shot on a crop body at ISO 5000, it is shot at ISO 5000.

While these cold hard facts are indisputable, it's only if you want to compare to different sensor formats that you have to start doing maths. If you don't, stop reading here.

While you can say it's the equivalent of a 27-88mm lens, due to the physical size of the entrance pupil (which can't alter at a given focal length and aperture setting), the equivalent aperture changes. (Take the lens set to 55mm, f2.8. The entrance pupil is 55mm/2.8, or 19.64mm. If you insist on calling 55mm 'equivalent' to 88mm, that fixed entrance pupil size means that at '88mm' the aperture ratio is 88/19.64, or 'f4.48'). Equivalent ISO can be calculated by multiplying by the sensor area ratio.

But, as I said, equivalence is only useful if you want to know how two different systems compare. If you only shoot one sensor size and/or have no interest in how your system is equivalent to anything else, it is irrelevant. As I said, f2.8 is f2.8. 55mm is 55mm. ISO 5000 is ISO 5000.

3
Lenses / Re: Canon EF 11-24mm f/4L Accepts Rear Gelatin Filter
« on: February 27, 2015, 06:20:02 PM »
Since this lens is already so huge and heavy, I wonder if it would have been possible to have a drop-in filter system for it. That would have been AWESOME! You could use variable ND filters and polarizing fitlers.
11mm focal length on a body with a 44mm flange distance requires a pretty heavy duty retrofocus design. Enlarging that BF distance to the levels required for a drop in filter as found in the super teles would be a step too far - weight, size and possibly optical quality would all suffer. Super teles due to their focal length alone have a very substantial BF which has compromise free space for a drop in filter together with space to accommodate a TC.

4
EOS Bodies - For Stills / Re: 5DS - effective resolution in mraw and sraw
« on: February 25, 2015, 01:07:10 AM »
I don't know if it still holds true but I recall that mRaw and sRaw used to only be able to PP in DPP, other software did not recognise them.
Out of curiousity, I gave it a go with my 5D2 in M-RAW. LR opens it fine, so with a bit of luck the same will hold true of the 5Ds. I have CC, so I am using the latest version of LR.

5
Call me a stickler, but I really don't understand why 50 MP vs. 21 MP is referred to as "resolution"; it is image size.
Resolution in optics is how well two adjacent points can be separated. That is a function of the optics, not the body/sensor.
Yes, resolution in optics is a function of the optics, not the body/sensor. But this question related specifically to the resolution of the body at different settings, not the resoltuion of the optics. That is a function of sensor/output files, not the optics.

Ok, strictly speaking, resolution should be measured in a unit of measurable detail per unit of distance, eg lines/mm or pixel pitch. But for a known and constant sensor size (and RAW, M-RAW and S-RAW all utilise an identical area), MP is equally as good.

Good24, here are your answers: (courtesy of http://www.usa.canon.com/cusa/consumer/products/cameras/slr_cameras/eos_5ds#Specifications)

RAW: 50.3 MP (8688 x 5792)
M-RAW: 28.50 MP (6480 x 4320)
S-RAW: 12.40 MP (4320 x 2880)

6
EOS Bodies / Re: Possible Canon EOS 5D Mark IV Spec Talk [CR2]
« on: February 22, 2015, 11:49:05 AM »
And how will a 5D Mark IV with 18 MP be postioned on the market against a Nikon D810, 36 MP or a D900 with 40 MP ?
Just because Nikon have made one line of bodies high MP doesn't mean Canon have to outgun them on that one metric alone with every single body. Surely the 5Ds/5Ds R have that niche covered in style?

7
Lenses / Re: which telephoto for travel?
« on: February 22, 2015, 08:27:02 AM »
I am currently in maui on vacation with my wife photographing humpbacks and birds and our kit consists of 70d + 70-300L that my wife uses ,my gear is the 6d and the 7d II and lens include 24-105 L -100 L macro and 100-400II with the 1.4x III for a little extra range for birds.

I am considering the new 100-400 (II).  How well does it AF with 70D and 7D M2 and the 1.4x III?
the 70D only supports AF with lens/TC combo's at f5.6 or larger through the viewfinder, so the 100-400 II and a 1.4x TC won't AF on the 70D - unless using live view.

8
Lighting / Re: Color temperature and light source
« on: February 22, 2015, 03:33:38 AM »
In very simple terms, yes, WB is set for the colour temperature of the light source, and it shouldn't matter what subject is lit, the WB should remain the same.

However, take into account reflected light, eg a flash of a known colour temperature bouncing off a coloured ceiling, and you're into a whole different ball game. And then of course, using the sun as a source, it's placement causes differences - blue light gets dispersed through the atmosphere, so the more atmosphere it goes through (think sunrise/sunset) to light up your subject, the less blue the light source is. And then there are other light sources with a known colour temp but a low colour gamut such as sodium lighting or some cheap LED's - there's very little you can do to correct that.

9
EOS Bodies / Re: Patent: Canon EF 300mm f/4L IS & Others
« on: February 20, 2015, 02:09:30 PM »
what are 4 and 6, if 1 is already 300mm f4? I mean, all three numbers show 300mm f4, but why exactly?
They've got multiple designs for 300/4 lenses in the pipeline, and while its highly unlikely three of them will make it into production (possibly none will), for whatever reason they felt the need to patent three.

10
EOS Bodies / Re: Patent: Canon EF 300mm f/4L IS & Others
« on: February 20, 2015, 02:05:25 PM »
Not familiar with all the numbers in this tab. What is BF?
Back Focus - the distance between the rear element and the focus plane (at infinity I beleive)

11
Lenses / Re: 70-200mm Mk I vs Mk II
« on: February 20, 2015, 06:01:01 AM »
The mk I 70-200/2.8 IS wasn't too shabby at f4, and would actually put in a half OK performance at f2.8 in the mid range of the zoom. However, use it near either end of the range and f2.8 didn't return much in the way of sharpness.

The new one is a whole different animal, producing amazing results at any focal length or aperture setting, and even with the 1.4x TC. The IS is greatly improved too.

I'm very glad I upgraded.

12
EOS Bodies - For Stills / Re: Coincidence or?? MP/SEC
« on: February 16, 2015, 04:28:26 PM »
Output data at 14fps would be JPEG, but the input data from the sensor would still be 14-bit. I don't believe Canon does any kind of downgrading on the bit depth of the ADC units (I've never found any information indicating as much anyway), so I don't believe there is a 12-bit 14fps read mode. The output data rate for JPEG (when writing to the memory card) would certainly be lower, but the input rate into the DIGIC processor would still be 14-bit.

It's difficult for anyone outside of the development team to do any more than speculate, but I'd argue that if the camera can really handle 14 bit readout at 14 FPS, then why force JPEG only on users? The buffer is still there, and if the readout and JPEG engine can keep up with 14 bits, the buffer should be able to too - so instead of forcing JPEGs on the user, why not give them a choice of a smaller buffer depth and raw? Card speeds only become relevant once the buffer fills up, and the target audience of the 1D X should in Canon's eyes be capable of deciding which trade off to choose.

I'm under the impression (falsely or not) that it's JPEG only as the readout doesn't support 14 bit CR2 files at 14 FPS.

13
EOS Bodies - For Stills / Re: Coincidence or?? MP/SEC
« on: February 16, 2015, 02:13:07 PM »
At full tilt, many Nikon bodies reduce the data per frame by dropping from 14 bit to 12 bit raw.

Canon don't offer that, but the 1D X does have compromises at 14 FPS other than the mirror staying up leading to viewfinder blackout and no AF tracking - the output is JPEG only. That's likely due to the sensor output dropping to 12 bit as a work around for the high data rate. If that's the case, the sensor readout and processing has gone from 12 FPS @ 14 bits to 14 FPS @ 12 bits - which is an identical data throughout.

Add bit depth into your calculations, and the 5Ds works out at ~443 MB/s.
The 1D X tops out at ~380 MB/s at both 12 and 14 FPS.

The 5Ds is no speed demon purely in terms of FPS, but that is an unprecedented data throughput for a Canon stills camera.

14
Good theory, but it's clearly not the well used 24MP Sony sensor. This uses a 1.6x sensor, not 1.5x. Even if it was a 1.5x with just the central 1.6x being utilised, the Sony 24MP sensor would only have 21 effective MP left.

15
EOS Bodies / Re: RAW file size of crop mode in 5Ds/5DsR
« on: February 10, 2015, 02:24:18 PM »
I am not seeing the information you quoted.  I do see the RAW info for full frame, but there doesn't seem to be any sizes for 1.3 or 1.6 RAW files.
http://www.usa.canon.com/cusa/consumer/products/cameras/slr_cameras/eos_5ds?WT.mc_id=C126149#Specifications

Scroll down to drive system, and look at the raw section of the table.

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