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Messages - Blaze

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16
Macro / Re: Canon MP-E 65 1x-5x 2.8 Macro Lens example photos
« on: April 09, 2012, 04:31:13 AM »
Sharpness takes a hit at small apertures due to diffraction blurring unless you use focus stacking, but such are the limitations of physics.

Here's an example at f/16:


17
Lenses / Re: Patent: Canon EF 2.8x Teleconverter
« on: March 28, 2012, 11:59:29 AM »

A 70-200 f/2.8 at 70mm has a maximum opening 25mm in diameter, agree?

A 70-200 f/2.8 at 200mm has a maximum opening... 25mm in diameter.

AFAIK, there's no physical mechanism opening the blades wider as the focal length increases. Rather, the zooming in optically magnifies that 25mm aperture such that it appears to be 71mm in diameter (at the 200mm example).

I see no reason they couldn't employ that principle in teleconverters.

That said, sure, I probably I read it wrong, hence me asking what they meant by that bullet point.


I don't think you understand the fixed f-number zoom lenses properly. If the 70-200mm had a maximum opening of 25mm at 200mm, then it would only be f/8 zoomed in. There is in fact a physical mechanism opening the blades wider as the focal length increases.


No, it has 2.8, because the pupil is magnified by the front element moving relative to the pupil.

If they could make the blades open to 71mm in the same form factor, they sell it as a 70-200f/1-2.8.

Zooming a lens doesn't mechanically widen the pupil. It optically magnifies it. 

http://www.dgrin.com/showpost.php?p=523730&postcount=2
There is a lot of mis-information on the Internet about how "constant aperture" zooms work, but the most lucid explanation comes from Bob Shell:

    Comments from Bob Shell (January 8, 2003):
    "An f-stop is the ratio between the focal length of the lens and the *apparent* size of the lens opening as viewed through the front. It must take into account the magnification factor of all lens elements in front of the diaphragm, because it is the size of the opening that the light "sees" as it passes through the lens, not the actual physical diameter of the diaphragm opening.
    It is this fact that allows companies to make constant aperture zoom lenses which maintain a constant f-stop when the focal length changes, because such lenses are designed so that the magnification factor (diopter value) of all elements in front of the diaphragm changes as focal length is changed to hold the aperture value constant."



Hmmm. It seems I'm wrong then. Thanks for the correction.

It still doesn't completely make sense to me though. If it's possible to magnify the image while maintaining the same f-number, then couldn't they make TC's that go in front of the lens without sacrificing aperture? And why even make variable f-number zooms?

18
Lenses / Re: Patent: Canon EF 2.8x Teleconverter
« on: March 27, 2012, 12:27:58 PM »

A 70-200 f/2.8 at 70mm has a maximum opening 25mm in diameter, agree?

A 70-200 f/2.8 at 200mm has a maximum opening... 25mm in diameter.

AFAIK, there's no physical mechanism opening the blades wider as the focal length increases. Rather, the zooming in optically magnifies that 25mm aperture such that it appears to be 71mm in diameter (at the 200mm example).

I see no reason they couldn't employ that principle in teleconverters.

That said, sure, I probably I read it wrong, hence me asking what they meant by that bullet point.

I don't think you understand the fixed f-number zoom lenses properly. If the 70-200mm had a maximum opening of 25mm at 200mm, then it would only be f/8 zoomed in. There is in fact a physical mechanism opening the blades wider as the focal length increases.

19
EOS Bodies / Re: So frustrated with new 5DmkIII - returning it!
« on: March 25, 2012, 08:15:29 PM »
Mine is pixel-sharp.

With a 24-105mm L. (Not considered the sharpest lens available.)

I think maybe you got a bad unit.

I'm delighted with the combination!


Hey FLEETIE

Can you post one of your shots? A JPEG version and possibly a link to the RAW as well? I'd love to see one!

I'm also loving my 5DMKIII - Images are looking sharp and very low noise :)


Maximum attachment size allowed is 4096kB (4MB), so I can't. The JPGs are 7 to 12MB.

I don't have any fancy web accounts that'll store files that size.

If you really want, give me your email address and I'll mail you a JPG straight out of camera.


You don't need any fancy web accounts. Just use something like minus.com.
(Note that unlike say imgur.com, minus.com leaves the metadata intact.)


Example:
Here's a direct link to an 8.61 MB JPG: http://i.minus.com/ibmN49uCtD9Jov.jpg
Here's a link to download the original 25.76 MB CR2: http://minus.com/m1FHpveLO/

20
EOS Bodies / Re: Weird Banding on shots....
« on: March 21, 2012, 10:50:51 AM »
How about situations like this where a flash is inappropriate?  Any other work-arounds in post-production or other camera settings (white balance, metering options) that might reduce it?OR,  Is this just a function of the higher ISO sensitivity?  I shoot in gyms like this all the time (7D/1dIV) using 1/800-1/1000,  up to ISO 3200-6400 and have never seen it.  Have I been 'lucky' that my shutter speed and the frequency of the flickering just have not been in synch, or has my camera been unable to detect it at these lower ISOs?

Based on my understanding this is solely a function of shutter speed. It's similar to the rolling shutter phenomenon and this would probably not be an issue with an electronic shutter. Your mechanical shutter does not expose the entire sensor at once. One curtain opens and another closes behind it. With fast shutter speeds both of the curtains move simultaneously. So the sensor is exposed in "slivers."

A portion of the "slivers" being exposed are darker and have a green color shift because the fluorescent lights had cycled while the shutter was in motion.

The article on focal plane shutters at Wikipedia has a diagram showing the function of the shutter. Based on my understanding, the aperture and sensor sensitivity will have little if any effect on the banding.

Gyms can have a variety of lighting types and not just fluorescent which might explain why some people don't see this or don't see it as often.

I've shot basketball and volleyball in gyms and never had an issue. I only discovered this issue when shooting at my son's karate school. Shooting at 1/160 gets me a large number of keepers and I don't see anything at all at 1/125. Flash kills off the banding completely. Now if I could get the instructor to get rid of the bright blue and pink mats which makes getting reasonable skin tones almost impossible...

The banding in the OP's photos may be attributed to a rolling shutter type effect, but having an electronic shutter wouldn't completely solve the problem of shooting under flickering gym lights. I have many hundreds of photos I've shot under these sorts of lights where the brightness and WB vary across the frame perpendicularly to the direction of the shutter movement (and thus cannot be a rolling shutter effect). The lights don't all flicker exactly in sync, which means for fast shutter speeds you'll often see variations due to the lights being in different parts of their cycle from each other.

21
Lenses / Re: Canon 50/1.4 focusing
« on: March 05, 2012, 10:56:48 PM »
I use the 50mm f/1.4 on my 7D occasionally. The auto-focusing is pretty unreliable compared to my other Canon lenses, especially in low light and close distances.

For that reason (and the fact that it's quite soft wide open), it's my least favorite and least used lens that I own.

22
Canon obviously can't please everyone, but the 5DIII really is a massive step up from the 5DII.

  • It now has a tougher, better sealed body (with optional matching quality built grip).
  • HUGE improvement in auto-focus.
  • Significant improvement in high ISO capability (on paper anyway)
  • Much faster continuous shooting
  • Tons of little improvements (screen, ergonomics, dual cards, viewfinder, HDR, etc.)

For my purposes, the specs are way more attractive than the D800. I have no need for 36 MP and the increased bother of dealing with larger files. Even with fast lenses, I'm very often pushing the limits of high ISO, so the 5DIII really wins there. 6 fps is just fast enough to shoot sports (although I'll miss the 8 fps on my 7D). The D800 only does 4 fps (you need a grip and crop mode to get 6 fps... very limiting).

For those that want MF resolution in a FF body for studio work, the D800E is probably more attractive. If this turns out to be a hot market, I'm sure Canon has something in development to compete with it.

As far as whether or not the price is "justified", that doesn't even seem like right question to ask. Are the improvements worth it to you? I'm guessing there's a huge demand for the 5DIII even at the current price point. If Canon can sell them at that price to willing customers, there's no reason they shouldn't. Remember, businesses are designed to make money. They might not even be able to match production to initial demand if priced sub-$3k.

Personally, I have no immediate need for the 5DII so I can afford to wait and see if the price comes down in the months to come and for reviews on sensor performance and real world testing to see whether or not it lives up to its specs on paper.

In my mind, it really is most of the good stuff from a 1DX in a smaller cheaper package. I would have loved for it to have 1080p @ 60 fps and 720p @ 120 fps video, a bit higher continuous shooting rate, the 1DX metering, and a $2500 price tag, but I realize Canon doesn't cater specifically to me and I can't always have exactly what I want at a price I can afford.

23
EOS Bodies / Re: 5D Mark III Full Spec List?
« on: March 01, 2012, 11:14:13 AM »
Currently I fail to see any magic in this camera, just as usual Canon's crippled update, whereas the price seems to indicate premium qualities.

In that sense Nikon has clear and understandable distinction - full package in all FF cameras targeting different auditoriums, against Canon's very expensive and crippled expensive option.

What exactly do you think is crippled about this? These specs look much more appealing to me than the Nikon D800.

24
EOS Bodies / Re: *UPDATE* Here's an Invite for March 2, 2012
« on: February 29, 2012, 01:11:20 PM »
I was looking on the Northlight rumor site.  They claim that a dealer was quoted as saying the price will come out at $3250 Euros.  That translates to $4,372.55 US dollars.

Camera prices don't translate according to exchange rates like that.

25
EOS Bodies / Re: The new 5D Mark III ?!?! PICS!
« on: February 27, 2012, 11:22:13 PM »
Where is the DOF preview button? Please tell me it's lockable...

The DOF preview on the 5DII a terrible implementation that made it more or less useless.


this was asked a few pages back.  Some have suggested that it may be the other side of the lens near the grip-similar to the 7D


The people suggesting that must not be familiar with the 7D.



The 7D has it on the same side as the flash button and lens release.

The 1DX however has various buttons on the other side.



Perhaps the 5DIII is similar.

26
EOS Bodies / Re: The new 5D Mark III ?!?! PICS!
« on: February 27, 2012, 12:28:06 PM »
Just a couple of comments.

First, the lens on the 1DX looks exactly like my 85mm f/1.2 L II from that angle. I think we can be sure it's not a Sigma.

Second, here's what the side of a 7D looks like:

http://a.img-dpreview.com/news/0909/Canon7d/side1.jpg

http://a.img-dpreview.com/news/0909/Canon7d/52_eur_001.jpg

The "A/V OUT DIGITAL" is a USB port. I would assume it's the same on the 5DIII.

27
Quote
Will the suggested 5d III specs satisfy your photograpy needs?

Too early to tell yet. I'm looking to upgrade to FF from a 7D and the 5DII just doesn't have the speed or AF I need for sports. The revealed specs for the 5D-next look promising but incomplete at the moment. If it's at least 6fps and gets a significant improvement in high-ISO capability and DR in addition to the rumored specs, then it sounds perfect for me. (1080p at 60fps and 720p at 120fps or better would be a lovely bonus.)

28
EOS Bodies / Re: Can someone debunk this Peter Lik picture... PLEASE!!!
« on: January 31, 2012, 12:20:25 AM »
This is certainly more than just a double exposure. (Obviously it can't be a single exposure since the moon is so much brighter than the stars and the shaded part of the moon is never darker than the sky beside it). It is clearly a composite of at least two separate images (with different composition, not just different exposure). This scene cannot exist.

Let's review the problems with it compiled from various people's comments.
  • The moon is in front of the clouds in the background.
  • The shadowed part of the moon must be opposite of the sun.
  • A full moon is always in the opposite part of the sky the sun, not in nearly the same direction.
  • The orientation of the moon is wrong. (It is rotated relative to how it would appear in reality.)

The moon was shot in a different part of the sky and then pasted into this image.

29
Wish I knew what this type of fish is called.

(Canon 7D + 50mm f/1.4 @ f/1.8, 1/200 sec, ISO 500)

30
EOS Bodies / Re: Canon Lightfield / Plenoptic Cameras?
« on: January 30, 2012, 11:00:42 PM »
You don't get something for nothing. There is a trade off between spatial resolution and directional/angular resolution. Basically the more megapixels you need, the less flexibility you have to refocus after the fact.

Of course having all the microlenses introduces further complications including diffraction limitations, chromatic aberrations, and aliasing. I've not seen an image from these type of cameras that looks very sharp.

If you really want to get into the details, I suggest the CEO of Lytro's thesis: https://www.lytro.com/renng-thesis.pdf

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