October 01, 2014, 12:13:08 AM

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Messages - weixing

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61
EOS Bodies / Re: Do Sensors sell the Camera?
« on: August 26, 2014, 01:01:31 AM »
Hi,
I know.... it's not like it's hard to do....
I can't think of anything at work that does not use at least 24 bit A/D and we have some test equipment that has 64 bit A/D and others that have 48 bit A/D running at 60Ghz sampling rates... I think that the last time I designed something with only 16 bit A/D was back in the 1980's....
Even though I don't know a lot about electronics I'll go ahead and wade in to water over my head.  While it may be easy to implement, it may have implications for the rest of the body.  Presumably, more precise sampling will draw more power proportional to the increase in precision: more bits of A/D will mean more components, all of which draw power.  Then the digital circuitry all the way from A/D to flash card has to be scaled-up to match which also draws more power.  All of this also generates heat which must be dealt with.  In my sophomoric opinion, this would result in slower framerate and heat issues for the sensor.  And that's not even considering the effect on battery life.  It's not impossible, but it's an extra set of engineering problems which incur greater cost, which affects retail cost and profit.

Also, why jump straight to 20 bit A/D when you can sell 14, then 16, then 17, then 18, then 19, then 20.   8)
    Hmm... Pentax use 22-bits ADC many years ago... on the Pentax K10D, but the raw file is only 12-bits... then Pentax K20D use back the 14-bits ADC... just wonder why they change back to 14-bits??

   Have a nice day.

62
EOS Bodies / Re: Are These The EOS 7D Mark II Specifications?
« on: August 22, 2014, 08:36:42 PM »
Hi,
   The specification look good to me:
1) No GPS - fine with me... I already had an external GPS unit which capture GPS signal way faster than 6D GPS and got map function.
2) No wifi - not importance to me... may be they got built in radio trigger, that's why cannot put wifi??
3) No 4K - no problem... running out of hard disk space, 1080p is good enough for my use... 1080p file size is already too large for me, but I do hope they had 1080p 1:1 video crop mode.
4) 20.2MP - enough for me, but I do hope they can improve the high ISO performance by at least half a stop compare to 70D and I might change my 6D to it.
5) Hope 7D2 had a silent shutter mode... very useful for shooting shy birds.

   Hope the pricing will be close to 6D, so I can just sell my 6D and get this one without spending too much...

   Have a nice day.

63
Third Party Manufacturers / Re: Sigma and Tamron OS/VC quirks
« on: August 22, 2014, 01:18:24 PM »
Hi,
I now own two third party stabilized lenses, the sigma 70-200 2.8 EX (there are a lot of letters and I always forget them) and the tamron 150-600. I've noticed a quirk they both exhibit that none of my canon IS lenses do: when the stabilizer engages, the frame tilts down what visually feels like about 5-10°. With the 70-200, it's not that bad, but at 600mm with the tamron, 10° is a lot.

Has anyone else noticed that kind of this happening? What's the explanation? Misalignment in the stabilizing optic? Maybe I'll shoot a video if nobody can picture what I'm seeing.
    My tamron 150-600mm will usually just "jump" (meaning that it'll return to the initially aiming point) a bit when IS is activated... sometime if the IS is not activated for a long time, the frame will move down a bit, but still very close to my AF point... at 600mm, the distance it move is around the size of my 6D centre AF point... not very much... my handshake is easily 10 times worst than that...  ha ha ha :-P

   Have a nice day.

   Have a nice day.

64
Technical Support / Re: Another my Stupid question = Sensor Sizes
« on: August 21, 2014, 10:14:05 PM »
Hi,
Obviously, the FF sensor takes in more light, but it is spread over a wider field of view and the light per pixel is the same.

But the output image (print, projected image, etc) is the same size, so the light gathered by the FF sensor requires less enlargement (attenuation) to achieve that output size, and this negates your argument.

So I believe you're mistaken: with identical technology, the size of the sensor is all that matters for low-light properties.  For ample-light IQ, total MP, AA filter, etc are definitely important for resolution.

I'm sure jrista will jump in here any minute to correct us all.  :-)
    No, for example a 36MP FF and 18MP FF using the same manufacturing technology, the 18MP FF will have better low-light properties as which pixel received more light than the 36MP FF.

Quote
   



Make the pixel smaller and you get more resolving power, but at the expense of less light, worse low light performance, and less flexibility with exposure times and apertures.


I believe the number of pixels a sensor has determines it's resolving power not the size of the pixel.  Large sensors with 18 (large) MP will resolve the same as a tiny sensor with 18 (tiny) MP.


    Pixel size will determine the resolving power (provided the lens and environmental condition are not limiting the resolution), so a smaller sensor will have better resolving power than a larger sensor of the same MP.

   Have a nice day.

65
Photography Technique / Re: APOLLO missions - image inconsistencies
« on: August 17, 2014, 09:00:54 PM »
Hi,
Thinking about it now, that would have been an exceptional feat to accomplish with the technology of the time!  So there's room for doubt.. and deception.
   The different between the Apollo period and now is that cost and safety wasn't the highest priority during the cold war period... landing human on Moon first is.

   Anyway, if the Moon landing is fake, USSR will sure know and make a joke out of it...

   Have a nice day.

66
Hi,
    Nice setup... I use an old Vixen GPD mount with motor drive... thinking of doing some astrophoto again (that's why I keep my EF 400mm F5.6L when I brought the Tamron 150-600), so thinking of adding GOTO to it...  ;D

    About the lens, IMHO, most telephoto zoom lens are not suitable for long exposure DSO astrophotograph... reason been most of them have zoom creep due to the heavy front element. I think may be the Canon EF 100-400mm is the only zoom lens that's suitable as it can lock the focal length.

    Anyway, there are a lot of low cost decent telescope in the market now that can produce very good result... IMHO, with a field flattener, most of them can produce better result than most super telephoto lens.

   Have a nice day.

67
Hi,
    Nice setup... I use an old Vixen GPD mount with motor drive... thinking of doing some astrophoto again (that's why I keep my EF 400mm F5.6L when I brought the Tamron 150-600), so thinking of adding GOTO to it...  ;D

    About the lens, IMHO, most telephoto zoom lens are not suitable for long exposure DSO astrophotograph... reason been most of them have zoom creep due to the heavy front element. I think may be the Canon EF 100-400mm is the only zoom lens that's suitable as it can lock the focal length.

    Anyway, there are a lot of low cost decent telescope in the market now that can produce very good result... IMHO, with a field flattener, most of them can produce better result than most super telephoto lens.

   Have a nice day.

68
Lenses / Re: Tamron 150 600 woes
« on: August 12, 2014, 12:49:41 PM »
Hi,

i was told (possibly by a tamron rep ) but don't hold me to that .that the problem is the fact that canon will not let tamron have the lens algorithm table to get it right most of the time ,whereas nikon and sony let them have access to theres .i don't know if this makes sense or is even the truth but most problems with this lens seem to be coming from canon users ,the pics i am seeing from the nikon ones are spot on ,with hardly any complaints from nikon users at all .
   i borrowed one for a day and in all honesty i was not impressed with a/f at all and would rather use a 400mm f5.6 plus 1.4tc on my 1D3 to get the  reach .


The problem with that oft-repeated theory is that Tamron makes lenses for Canon. They do for Canon as well. They couldn't very well do that if Canon didn't give them all the information they needed, could they?
They reverse engineer, with obvious shortcomings.

No, they don't. Why would Canon ask them to build a lens for their cameras and then not give them the specs they need?

Remember, it's Sigma that has AF problems with nearly all of their lenses. Most Tamrons work fine.
    No, Canon didn't give Tamron or any 3rd party lens manufacturer their EF mount information and protocol... they (3rd party lens manufacturer) reverse engineer it. Take a look at this article (although it's a very old article, but I think should still be true today):
http://kbsupport.cusa.canon.com/system/selfservice.controller?CONFIGURATION=1011&PARTITION_ID=1&secureFlag=false&TIMEZONE_OFFSET=&CMD=VIEW_ARTICLE&ARTICLE_ID=9820

    Anyway, my Tamrons 150-600mm AF work quite well except that when in AI servo mode, I notice sometime it'll go out of focus momentary even if the subject is not moving... but have not try to reproduce the issue... will try when got some free time.
 
    Have a nice day.

69
EOS Bodies / Re: Patent: Dual Pixel Phase Detect AF While in AI Servo
« on: August 12, 2014, 12:23:28 PM »
Hi,
    I personally won't get a DSLR with EVF for birding/wildlife... it'll "eat" the battery very fast. If it's a hybrid (with option of using either optical or EVF), then I don't mind.

    Anyway, may be the Dual Pixel Phase Detect AF is use to do fine adjustment to the AF when the mirror is up during the image capture phase...

    Have a nice day.

70
Hi,
Hi,
   Today, I do a compare shots on FF vs APS-C on a real bird under real life condition... only manage to try out ISO 1600 and ISO 3200 as start to rain very heavily after this. I just open them using lightroom 4, took a screenshot, paste on paint and saved as jpeg.
Test Condition
Camera: Canon 6D (left) vs Canon 60D (right)
Lens: Tamron 150-600mm @ F8
Subject: Stork-billed Kingfisher at around 18m (this is the only real bird that I can find that will stay at the same place for extended period of time with minimum movement).
Weather: Cloudy

After looking at the compare shots, my initial conclusion is that the 60D sensor doesn't seem to have a significant details advantage (if any) under real life condition (at least this seem to be true when using the Tamron 150-600mm lens) over the 6D and the 6D (up to ISO 3200) doesn't seem to have a real noise advantage if the 60D image was scale down.

   Have a nice day.

PS: The CanonRumors website seem to scale down the screenshot image (actual size is 1920 x 1080) to fit the website frame... to view at actual size, need to click on the image and using the scroll bar below the post to scroll through the image... or is there a setting to show the image actual size??

Very interesting results. Congrats on finding a bird that would sit still the entire time you took the shots. :D That's definitely the kind of bird you need.

To really truly compare, you would need to overlay the two images on top of each other, and upscale the 6D images so the bird was the same size, then overlay them directly on top of each other (Photoshop's difference layer blending mode makes the positioning very easy). Then you can swap back and forth, and really see the difference. It's pretty much impossible to objectively determine any real differences when looking at the images side-by-side...it becomes almost a pure subjective judgement.

The only other thought I have is the lens used. The 150-600 is a good lens for it's price class, but I can tell it does not resolve the same kind of detail as the EF 600 f/4 II. I am able to resolve fine feather and fur detail even at very high ISO, something I don't see in your images. It doesn't necessarily invalidate the test, however it does throw in a major factor that affects results. The moon is a bit of a different kind of subject than a bird, given that it is primarily seeing limited rather than diffraction limited, so using 1200mm f/8 does not limit resolution the way it would with a terrestrial subject. If I were to do a bird test...I would probably use the 600 at f/4.5, which seems to be the absolute sweet spot of my lens.
    I had no doubt that EF600mm F4 II with it's 150mm front element will resolve more details compare to my 95mm front element, but I'm $$ limited... ha ha ha  ;D

    Anyway, the sky is cloudy and the bird is under the shade... so I think the details are a bit more difficult to resolve under this flat lighting condition.

    Have a nice day.

71
Hi,
   Today, I do a compare shots on FF vs APS-C on a real bird under real life condition... only manage to try out ISO 1600 and ISO 3200 as start to rain very heavily after this. I just open them using lightroom 4, took a screenshot, paste on paint and saved as jpeg.
Test Condition
Camera: Canon 6D (left) vs Canon 60D (right)
Lens: Tamron 150-600mm @ F8
Subject: Stork-billed Kingfisher at around 18m (this is the only real bird that I can find that will stay at the same place for extended period of time with minimum movement).
Weather: Cloudy

Below are the shots:

6D vs 60D ISO 1600 (1:1)


6D vs 60D ISO 1600 (2:1)


6D vs 60D ISO 1600 (1:0.5)


6D vs 60D ISO 3200 (1:1)


6D vs 60D ISO 3200 (2:1)


6D vs 60D ISO 3200 (1:0.5)


   After looking at the compare shots, my initial conclusion is that the 60D sensor doesn't seem to have a significant details advantage (if any) under real life condition (at least this seem to be true when using the Tamron 150-600mm lens) over the 6D and the 6D (up to ISO 3200) doesn't seem to have a real noise advantage if the 60D image was scale down.

   Have a nice day.

PS: The CanonRumors website seem to scale down the screenshot image (actual size is 1920 x 1080) to fit the website frame... to view at actual size, need to click on the image and using the scroll bar below the post to scroll through the image... or is there a setting to show the image actual size??




72
Reviews / Re: DxO reviews Sony A7s: king of low light photography?
« on: August 08, 2014, 07:27:23 AM »
Hi,
   As a Canon DSLR user, I come to canon rumors to read any news, reviews and advice on Canon camera product, so quite curious why some people come to a Canon forum just to bash Canon camera and bash anyone who think Canon DSLR is a very good camera (may not be the camera that produce the best IQ now, but overall a very good general purpose camera)??

   Have a nice day.

   

73
EOS Bodies / Re: Canon Doing Market Research on Medium Format?
« on: August 06, 2014, 12:09:43 PM »
Hi,
... there are just more leaks coming from Nikon.

^^This

I've said for years that Canon's weather sealing is superior to Nikon's, and the greater number of Nikon leaks just proves my point.

 ;)
    This is a good point.... Ha ha ha... ;D ;D ;D

    Have a nice day.

74
Hi,
I actually need to understand the process of converting the radiation received on the sensor to the RAW file - is the RAW file really the RAW data?
In addition, data describing the sensitivity of the sensor (R, G, B) through the spectrum would help me a lot, as well as understanding the issue of the effect of the ratio between the CCD RGB receptors (1:2:1).
Gilad
    Not sure what you looking for, but this website might help you: http://www.astrosurf.com/buil/cameras.htm (some of them not in english). Anyway, I think you should check with the Astronomy forum (such as cloudynights) as many Astrophotographer use mod Canon DSLR for imaging.

     Have a nice day.

75
EOS Bodies / Re: EOS 7D II Specs Listed on KDrama Stars
« on: August 01, 2014, 01:03:30 PM »
Hi,
Forgot to add the 20MP sensor sounds like the 70D sensor.
    I think 20MP for an APS-C sensor is a nice resolution... as long as the sensor high ISO performance is better than 70D by 1 stop, then I might change my 6D to 7D2.

   Have a nice day.

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