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151
Lenses / Re: 5D MKIII w 70-200 2.8II using a 1.4x vs 2x extender
« on: May 17, 2012, 05:11:47 PM »
I am quite disappointed with the performance of this exact combination.

Yes, the results from the optical magnification of the 1.4X III converter are better than interpolating the image to larger resolution. However, it noticeably diminishes image quality and contrast. Perhaps resolution might be fairly high, but the punch just isn't there for me. For an equivalent, I would say that the 7D with the 70-200 mm II is just as good as the 5D3 with the 70-200mm II + 1.4X. That's not supposed to be a positive comparison. I used both combinations for thousands of photos just a few days ago.

It's better if possible to just get closer with the 200mm lens and forgo the 1.4X converter. The 1.4X III converter does amazing things with a lens that is far sharper to start with like the $5,000+ exotic lenses.  But the 70-200 II lens with its huge number of elements doesn't exceed the camera's resolution by a sufficient margin to maintain its quality when combined with a teleconverter. Only the lenses like the 300mm f/2.8, etc., can do that.

152
Lenses / Re: Help! I think I got a bad 16-35
« on: May 15, 2012, 12:40:02 AM »
Wish someone would have told you that the bad part of the image was out of focus and saved you from sending off and getting a second "bad" copy of the lens.

The fact it is out of focus can be differentiated from lens sharpness or lens aberrations by the way the image looks. It is really weird that it is out of focus, however. It could be the camera sensor as someone mentioned.

There are two aspects in which the sensor might be to blame. Part of it is just the sensor is not very sharp, as you can see even in the center of the frame. The Canon 7D does not have the best sensor. No matter how low of ISO you go there is always some mushiness at pixel level. But clearly the center of your images are much sharper than the left side. So there is more to it than sensor image quality. Maybe there is also an issue with sensor alignment.

One way to find out if the lens is sharp on the left side, and the sensor is skewed, is to use live view to focus, and move the focusing box to the left side and center it on a very well-defined subject/object in the image. Use a tripod when doing live view to make extra sure, because hand movement does affect the camera's ability to determine the exact focus. The live view focusing mechanism feeds directly from the image sensor, so even if the sensor is out of alignment, it will still obtain focus on the sensor for the desired object--but then the rest of the frame might be out of focus.

It could be field curvature, but your f/7.1 image ought to have had plenty of depth of field to deal with that problem.

Wide angle lenses are notorious for their need to have the camera they are mounted on built to super precise lens mount tolerances. They have a lot of depth of field, but the back focus distance is so short (hint, due to the short focal length) that just a few millimeters can change focus from infinity to a few inches away.

For the photographer this means depth of field is very generous, but for the camera manufacturer, it means the lens mount has to be ultra carefully made to line up exactly with the corresponding lens. People have had similar trouble with the Nikon 14-24mm.


153
EOS Bodies / Re: 5D3 price drop?
« on: May 13, 2012, 06:47:28 PM »
Is $1,300 really worth an AF system, some nifty added features, and slightly better performance?

Every damn penny :)

Right on, V8. The most any photographer can do is nail the exposure, the perspective, timing, etc. The autofocus is something that a still photographer operating on their own cannot do, and must rely on the camera for. The days of the 80s are gone when anyone pretends to be able to keep perfect focus on a pole vaulter with manual focus, for instance.

For me the entire price of the camera was devoted to the autofocus system... otherwise, I would have been more than happy with extra copies of the cheaper 5D II.

154
Lenses / Re: Selling Lenses to Adorama Used Store
« on: May 12, 2012, 10:52:02 PM »
I have sold two cameras and some lenses to Adorama. I made the mistake of sending them several items at one time.

They told me they didn't "want" some of  the items, and yet offered me $1,000 for all of them. I had given them a list of everything before sending them my items, and they said they wanted all of it, and offered a estimate of $1,900 to $2,100.

I held them to their word about sending the items back, and they started to act reluctant, and got some managers. Finally they quoted me a price on each individual item, and I accepted three of their prices (D90 for $450, 50mm f/1.4 for $175, etc., all in mint condition). They really did a good job of making me think that these were the best prices I could get, about $25 under what they could re-sell them for. (Ridiculous! I think I saw my exact same D90 on sale at their website for $800 the next day). They did send me back one camera and one lens.

I ended up getting $950 for about two-thirds of my stuff, but I could have received at least $500 more on Craigslist. That was before I had tried Craigslist.

I have since sold an equivalent lens for $100 more, an equivalent camera body for $250 more, etc.
I would never use Adorama again to sell my used equipment to.

Regardless of where you sell your used equipment, to be successful, you must be willing to give the buyer a good bargain. I see so many posts on the bulletin boards of big companies of people trying to sell their cars, cameras, etc., for MORE than what they paid for them long before. That's goofy. Even if I have something brand new to sell, if I changed my mind for example, I still take off at least 10% from what I paid just as the "price" of my own stupidity for buying something I didn't need, and a courtesy to the purchaser, no matter how good of a deal I got originally.

155
EOS Bodies - For Stills / Re: 5D3 Dynamic Range
« on: May 05, 2012, 09:31:22 PM »
helpful,

Since you yourself pointed to Emil Martinec's website, I'm curious why you're still talking about rounding errors when he shows, rather convincingly, that cameras as of ~2008 didn't really benefit from even a 14-bit ADC b/c, essentially, noise is being oversampled at that point. Canon 5D Mark II's noise level at ISO 100, for example, is almost 6 ADU. That means that noise is being oversampled & it is unlikely that higher bit depth would lead to a more accurate representation of the signal since the signal itself can vary by ~6 ADU.

If the noise level were 1 ADU or less, I would agree that there could be rounding errors due to quantization. But as it stands, Martinec's findings seem pretty convincing to me.

So I'd like to hear your counterargument.

Thanks.

Right now the 14-bit data per color channel in the RAW is scaled appropriately to store the dynamic range of the camera's sensor, whatever that might be. If the scaling was changed, then the image from the camera's sensor could actually contain much more data. It's all integrated into hardware and firmware, so camera manufacturer's like to tell a little white lie and say that "RAW" is exactly what the camera is getting, i.e., coming through the lens. But the analog data always has more available than after analog to digital (ADC) conversion. True, the semiconductor components mess up the analog signal a lot, but there is still no reason to arbitrarily limit it at 14-bits.

I'm sorry for being harsh about your comment. It just seemed ironic to me why RAW would always be assumed to represent the maximum that "nature" has to offer--"nature" being the signal. 14-bits is an arbitrarily chosen number--a compromise.


156
EOS Bodies - For Stills / Re: 5D3 Dynamic Range
« on: May 05, 2012, 08:57:10 PM »
Quote
Quote
Quote from: helpful on May 04, 2012, 05:39:39 PM
A really high DR better than the 5D3 doesn't really help. As I have explained in previous posts, a lower DR actually stores more data and detail from a scene than a camera with high DR. Ideally the dynamic range would match the scene's DR. Canon's DR probably fits more scenes better than Nikon's. If the dynamic range is higher than the dynamic range intrinsic to the scene, then it actually makes the picture worse (less fine variations in detail of recorded luminosity).
This is false. Increasing the sensor DR will either give you more headroom before clipping, or less noise in the shadows. In both cases, you gain information (for some scenes there might be no data to record there, still you loose nothing).
Quote
In a low dynamic range image (like a frame filled with nothing but green grass), the histogram of a high DR camera like both the 5D3 and the D800 show nothing but a thin peak of data that was recorded. This means lots of detail is being lost because not all 14-bits are being used.
This is false. Most cameras are noise-limited, not quantizer level limited. This means that once the signal reach the ADC, there is (at most) 14 bits of information from the saturation level and down to the noise floor.

Well done clearing up that misinformation, hjulenissen  :)

In your comments there are some mistakes, or perhaps you just read my first sentence which was not clear except in its original context.

* You don't gain information when DR is increased--you exchange one type of information for another. Unless more bits of data are recorded, there is a tradeoff when DR is increased.

I did make one mistake. I should have quoted what I was referring to at the end of the sentence, "A really high DR better than the 5D3 doesn't really help." I was referring to the case being discussed when the scene does not contain more stops of dynamic range than the range already available in the 5D3.

Increasing the DR range of the recorded image does lose data for a scene that does not contain that large of a dynamic range. This is just a mathematical fact--anyone know of the pigeonhole principle? You can't have a RAW file that contains 14 stops of DR and contain as much information in each stop as a RAW file which contains 12 stops of DR. Both RAW files contain 14 bits per color channel, and you can't store those extra two stops without losing data somewhere. The data is lost because the variation between slightly larger changes in color or intensity is "rounded off" to the same value in order to achieve higher DR.

I would like to point out that you actually realized the truth, but didn't grasp it. At the end of your remark, you said, "for some scenes there might be no data to record there, still you loose nothing." So if there is "no data to record there," then that means nothing is recorded there. You may think, "Well, a pixel IS recorded" and so there is no loss. But there is something lost--because that pixel that was recorded could have been recorded with a gamma value closer to one (depending on whether encoding or decoding is being referred to, it could be less than one or greater than one) and stored more tonality and detail.

I am not just speaking off of mathematical logic, but out of my knowledge, training, and education. I have my Ph.D. in mathematics and my field is inverse problems and mathematical imaging. I have multiple articles on the subject published, and the latest is pending publication. These are in top journals--the cheapest of which costs almost $1,500 British pounds for a yearly subscription.

I am also not just a theoretical textbook person. I just got back from spending the entire day photographing.

My purpose is to be helpful through my knowledge, for free and anonymously. You can take it or leave it.

* The last sentence is completely unbelievably painful to even read:

"Most cameras are noise-limited, not quantizer level limited. This means that once the signal reach the ADC, there is (at most) 14 bits of information from the saturation level and down to the noise floor."

That sentence is equivalent to worshiping RAW and saying that 14 bits is the end-all, be-all of everything--the most data that can possibly be contained in an image. If that were true, it wouldn't even be possible to change the ISO level on the camera, because the camera would be recording everything that could be recorded.

There is a compromise in everything. Isaac Newton made the mistake (based on 3rd-party eyes that he trusted better than his own vision) of thinking that there was no diffraction, and hence, he wrongly believed that an infinitely small aperture would be perfect. Likewise, a high dynamic range does not comes without trade-offs, unless a higher quality image format is introduced to store the additional stops of data. Personally, I am advocate of a 48-bit color (3x 16-bit RGB) + 16-bit logarithmic luminosity channel, like Sony's new RGB+W encoding, except with more bits to fit into the current processing standard of 64-bit "words" (i.e., chunks of data).

We can think of these encodings all day long, but no one has control of the market, and no one knows what will be successful.


157
EOS Bodies - For Stills / Re: 5D3 Dynamic Range
« on: May 04, 2012, 07:16:33 PM »
Shooting JPEG you will never see a difference

False.
How many stops of dynamic range do you get in jpeg that is different from antone else? Jpeg is 8 bit no matter how many stops you get in raw

For a linear DR it is a DR of 8 - which is why specialist printers are needed to get more.

I hate to say anything critical to anyone, and you are both correct. JPEG has 8 bits of data per channel. And a statement involving the word "it" can always be assumed true--we have no idea about the object to which "it" is referring.

However, you are saying something correct and then jumping to a completely unrelated conclusion. Here's the missing information:

* JPEG is not encoded with linear gamma, and never has been with any digital camera.

"If images are not gamma encoded, they allocate too many bits or too much bandwidth to highlights that humans cannot differentiate, and too few bits/bandwidth to shadow values that humans are sensitive to and would require more bits/bandwidth to maintain the same visual quality."

* One bit and one stop have nothing to do with each other. It's also completely ridiculous to define dynamic range in terms of bits--it is only meaningful if defined in terms of stops.

If you have ever taken a class about encoding mechanisms, one of the first things one learns is, "The first thing to remember is that bit depth and dynamic range are NOT the same thing. It is going to sound much the same, but it's not."

The terminology used on this forum is sometimes as silly as someone saying, "I am going to itch my mosquito bite" when they mean "scratch my mosquito bite."

If you have ever taken a picture with part of it dark or part of it bright, you are seeing the effect of dynamic range. It has absolutely nothing to do with the file format. RAW extends the dynamic range provided that the same gamma curve is applied in the image encoding.

An increased dynamic range in the camera has a proportional effect on the dynamic range of both the JPEG and the RAW image. You can understand this if you will be patient enough to consider the example of an interval of real numbers.

The RAW image corresponds to the interval [-x, x]. The JPEG image corresponds to the interval [-cx, cx], where c is between 0 and 1. A change in the dynamic range corresponds to a change in x. The effects on both the RAW and JPEG images are proportional to one another.

One good article to read is this one:

http://theory.uchicago.edu/~ejm/pix/20d/tests/noise/

It also talks about noise in addition to dynamic range. There are books to read about this subject as well.

158
EOS Bodies - For Stills / Re: 5D3 Dynamic Range
« on: May 04, 2012, 05:40:21 PM »
Shooting JPEG you will never see a difference

False.

159
EOS Bodies - For Stills / Re: 5D3 Dynamic Range
« on: May 04, 2012, 05:39:39 PM »
A really high DR better than the 5D3 doesn't really help. As I have explained in previous posts, a lower DR actually stores more data and detail from a scene than a camera with high DR. Ideally the dynamic range would match the scene's DR. Canon's DR probably fits more scenes better than Nikon's. If the dynamic range is higher than the dynamic range intrinsic to the scene, then it actually makes the picture worse (less fine variations in detail of recorded luminosity).

The only part of the 14-bit RAW or 8-bit JPEG data that is really worthwhile is the part where the histogram shows data has been recorded. In a low dynamic range image (like a frame filled with nothing but green grass), the histogram of a high DR camera like both the 5D3 and the D800 show nothing but a thin peak of data that was recorded. This means lots of detail is being lost because not all 14-bits are being used.

Don't get me wrong. I'm not saying that there is "empty" data in most of the picture. There is a color and brightness value at every pixel. But the variations in brightness that could be recorded if all 14-bits were adjusted to a 2-stop DR are simply lost, because the camera is always trying to record a 9 stop or 10 stop DR, for example. The variations in brightness can be recorded much finer, just like with slide film, with a good sensor that has LESS dynamic range.

High or low dynamic range can't be held against a camera, any more than someone can say negative film is "better" than slide film, or vice versa.

160
Lenses / Re: Canon 85 1.8 vs. Sigma 85 1.4
« on: May 03, 2012, 06:31:06 PM »
The Canon is good for small prints and focuses like the wind--in the highest class of fast focus. But it's not useful as a picture-making machine below f/2.8 due to the low sharpness, low contrast, not to mention the purple fringing (I don't really care about that, since it is for the out-of-focus areas--I just care that the in focus areas are extremely sharp, and they are not sharp below f/2.8 ).

There are a lot of inaccurate reviews of the 85mm f/1.8 saying it is sharp, but they're using it in a variety of circumstances shooting on automatic and most of their review photos are f/2.8 or above, lots of f/5.6 shots, etc. For those the 85mm lens is world class. For this reason I own two copies, and two copies of the similar 100mm f/2.0 as well. The same comments apply to the 100mm f/2.0 lens, despite the fact that Ken Rockwell says the 100mm f/2.0 has 5.0/5.0 perfect optics. He is talking about photos that are not near f/2.0.

But when I need those apertures below f/2.8, then the Canon f/1.8 is simply not an option. Occasionally a picture is good enough at f/2.0 that I think there is hope, but it just isn't possible to call it sharp. The fast focusing sometimes makes up for it. To be fair, I made a 20x30" enlargement for someone two weeks ago that was shot at f/2.0 with the Canon f/1.8 lens. It can be done, but it's not pretty.

The Sigma on the other hand is three steps backwards in terms of focusing speed, but that still puts it far ahead of the 85mm f/1.2L in that area. The one problem that I hate about my copy of the Sigma (I've had it for 1.5 years and shot hundreds of events with it) is that it just doesn't do focus tracking properly. It focuses plenty fast enough even to take basketball photos, but it doesn't track movement after focusing, but waits for a moment. So I have to keep my finger off the shutter, and then push it at just the right instant so that when it is locking on it will actually track the motion in order to lock on, and then I get a perfectly focused shot.

It has no trouble locking on to a moving object, but it would be a lot easier if it would keep on tracking it so I didn't keep having to lift my finger up and down. I think there is something messed up with the algorithm in my first lens. I have another one arriving this week (20% off from Amazon with the purchase of a Canon body that I ordered) and I am hoping that it will be different.

Image quality from the Sigma f/1.4 is unbelievably good. That's all there is to say. Some tests have shown that it is better at f/1.4 than the Canon 50mm f/1.4 lens is at f/5.6.

In theory that's possible since the effect of diffraction is much more negligible at f/1.4, but in lens manufacturing it's pretty hard to make a diffraction limited lens faster than f/5.6. (Diffraction limited means that the lens design is so good that the only factor limiting resolution is diffraction. If this were the case with an f/1.4 lens, then it would have resolution 16 times higher than an f/5.6 lens.)

161
Lenses / Re: Trouble with my Canon 24.1.4 ii lens at 1.4
« on: May 02, 2012, 06:40:00 PM »
Agreed. Focus and recompose is a good technique for point-and-shoots or cameras with a single focus point AND a relatively small aperture (big f/number, to clarify for anyone who thinks aperture means f/number and is confused).

But it won't work with a shallow depth of field lens because the plane of focus is designed to be a plane so that the lens will focus perfectly on a flat wall (the famous "brick wall" lens test).

* When you focus and recompose the distance remains the same, so an uncorrected lens would still be in focus.
* But lenses are "corrected" to keep a flat subject in focus, and so when you recompose the shot, the plane of focus is rotated at the same time. The plane of focus doesn't intersect the subject anymore after recomposing the shot. Rotation of a plane shifts one half-plane behind its original distance, and the other half-plane closer than its original distance. Since the subject is at the same distance, things clearly won't line up anymore.

162
Lenses / Re: Trouble with my Canon 24.1.4 ii lens at 1.4
« on: May 02, 2012, 02:17:37 PM »
Great photos on your website, Louis. This one is strikes me as better than many famous versions of Yosemite Falls:

http://www.louisamore.com/landscape/2.jpg

It looks like the ground at the bottom edge is "earth" and the falls are pouring from "heaven."

163
Lenses / Re: Trouble with my Canon 24.1.4 ii lens at 1.4
« on: May 02, 2012, 02:06:17 PM »
Louis, I know exactly what you are talking about. Autofocus microadjustment will not reliably fix your problem, although that would be a great option for the 5D Mark III.

Even using the center point will not. The 5D Mark II has a problem with this particular lens in my experience. What will work is using lifeview autofocus (very slow) but that will nail the focus on still objects that the focus selector is centered on.

The lens itself has extremely sensitive and accurate autofocus, but the 5D2's phase-detection autofocus just rushes to an approximate focus  point and then leaves it there despite a slight mis-focus. Focusing on infinity and trying again will result in another slightly random focus shift. That's why you are needing to take a whole bunch of pictures in hopes of probably getting one that is sharp on the desired focal point.

Update: By the way, the same lens works fine with the 5D3 and my 7D cameras.

164
Sounds to me like the emperor who had no clothes! If such a kind of glass really existed, would it be able to refract light? Anti-fogging, self-cleaning, etc., seems like it is just a mist with no refractive properties. Really, I don't know why I'm responding to this post... just happened to pop up in front of me at the wrong time. :)

Like the second poster mentioned, it may be impossible to make a lens out of it. If it really exists, then perhaps it would be a great window glass, to shoot photos through. But it might not refract sufficiently to actually make a lens out of it.

165
Lenses / Re: Seeking lens in the 85-100mm range
« on: April 30, 2012, 07:55:36 PM »
There is only one choice for you in my opinion, given the prime lens consideration and the focal length range. That is the Sigma f/1.4 85mm. It is astonishing, really--more useful than the Canon f/1.2L. I actually ordered a second copy today. It's fast enough to shoot basketball, and by fast, I mean both the f-number and the focusing speed and accuracy. My first copy did need considerable microfocus adjustment, however. Afterwards it is super sharp across the board; er., I mean, across the frame.


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