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Messages - neuroanatomist

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6166
Too bad.  The lensauthority.com website is devoid of company information beyond a contact email.  Their terms seem the same as lensrentals (3-day inspection period, 90-day warranty).  Similar information about the specific lenses, too.  So, could be them.  Domain name is registered by proxy, whereas lensrentals.com lists the business and Roger as contacts.

Time will tell...

6167
Lenses / Re: What lens delivers the strongest background blur?
« on: July 16, 2013, 06:41:49 AM »
It is those two factors together, along with subject/background distance relationship determine the lens's ability to "blur the background"

When you are comparing a fast wide angle with a slow telephoto, it becomes complicated since you can't flat out say which one is better at blurring background, it depends on how far the background is to say which one is better!

Correct.

While the plotted data are useful, our backgrounds are not often infinitely far away (or far enough to be treated as such).

For anyone who's interested, Bob Atkins wrote a calculator for background blur that accounts for lens properties (as in the plot above) as well as subject distance and foreground/background distances.

http://www.bobatkins.com/photography/technical/bokeh_background_blur.html

6168
Lenses / Re: What lens delivers the strongest background blur?
« on: July 16, 2013, 03:15:45 AM »
Excellent, thanks!

6169
Lenses / Re: Dxo tests canon/nikon/sony 500mm's
« on: July 15, 2013, 11:20:06 PM »
...
They should rename their Overall Scores to a Camera Basic Score and a Lens Basic Score, so we could abbreviate them for what they really are: BS.  Actually, that's probably giving them too much credit, because real Bovine Scat makes good fertilizer, whereas DxOMark's BS has no real-world utility.

Your assertions of DxO publishing BS are just as BS as their results because you don't know how they calculate their "lens score" and thus you have to make up reasons as to why it is so. Yes, you're compounding the BS by stating that they're publishing BS. Just don't buy into it.

Except I'm not scoring lenses without disclosing my methods. In my scientific publishing, I must fully disclose my methods such that another scientist can duplicate my experiment.  DxOMark is clearly not held to the standards of peer-reviewed scientific publications. (Which is reasonable, as they're not publishing in scientific journals, but only to their own website - so, they can make up 'data' or 'scores' if they choose, change those data post hoc without explanation, whatever they want.)

We don't know what's in their black box? They don't say. Why not? If someone is hiding something, it's usually for a good reason.  Could be as simple as maintaining a competitive advantage (against who, I have no idea).

Clearly, I don't buy into it. Sadly, I suspect many people do...

6170
I am not sure I agree with this (but I very well could be wrong).  My experience is based on shooting through zoo fences with my cousin on APS-C and me on full frame.  I could swear there were times we had the same lens length and aperture and yet I could blur out the fence and he could not.  I have heard that full frame cameras have a shallower depth of field and this experience seems to confirm that.  Am I just imaging things?

Sorry, but probably, yes. If you were, in fact, using the same lens and aperture and not changing magnification (distance), and were the same distance from the fence, the blur would be equivalent.

6171
EOS-M / Re: Share your thoughts - M pricing
« on: July 15, 2013, 07:14:09 PM »
If you don't mind white box or gray market, they can be had on ebay for $120 on up. BigValue has them for $154 right now. I picked up mine as a white box for $131 and I absolutely feel the lens is worth that much. The $250 retail price is another matter. As to long term, we don't even know whether Canon USA is going to continue carrying the M "system" at all, so it's difficult to say.

Do the white box items come with a warranty?

Hard to say. I bought my M kit w/22mm from B&H. When I registered the camera, I only included the serial # for the camera as there was no option to include a second serial # for the lens. I can't even find a serial # for the lens, but one is listed on the kit box, so I guess there must be one. Ditto for the zoom. If there is a serial #, I can't find it. Personally, I'm not worried about it. The lens works fine and is surprisingly sharp. I would like to pick up a fast prime or two, but unless Sigma steps up to the plate, that may never happen.

I actually didn't find the body-only, just the M + 22 kit.  Regardless, registration is irrelevant for warranty purposes, what you really need is proof of purchase (e.g., your B&H invoice).

6172
Canon General / Re: online reviews & fanboys
« on: July 15, 2013, 06:31:43 PM »
Quote
A person who sows discord on the Internet by starting arguments or upsetting people, by posting inflammatory, extraneous, or off-topic messages in an online community (such as a forum, chat room, or blog), either accidentally or with the deliberate intent of provoking readers into an emotional response or of otherwise disrupting normal on-topic discussion.
I bet this fits many members here, too... 

http://en.wikipedia.org/w/index.php?title=Troll_(Internet)

6173
EOS-M / Re: Share your thoughts - M pricing
« on: July 15, 2013, 05:33:16 PM »
The EF-M 18-55mm (just like the equivalent EF-S lens) will never be a good value when bought alone. It's a kit lens, and only a good value when bought as such.  Now that I have the M + 22mm, if I get the 18-55 it will be in a kit with an updated M.

Mount adapter prices will probably come back down (I was fortunate to get mine from Amazon before the prices started rising).

6174
Wrong: the dof calculator also calculates the circle of confusion. http://dofmaster.com/dofjs.html

The technical mumbo-jumbo can be ignored.

Sorry, but then I suggest that you just ignore it, instead of calling others' correct statements wrong based on your misunderstanding.

FYI, DoFMaster doesn't calculate CoC, it assigns a standard value based on sensor size. It uses that assigned value to calculate DoF.

6175
EOS-M / Re: How do you carry your EOS-M?
« on: July 15, 2013, 02:38:22 PM »
...at home, my current M kit fits nicely in a Pelican Storm im2050 with dividers. 

Canon (especially Canon USA take note  ;) ): there's room in the case for a couple more items, such as the recently-rumored new flash for the M line above the 90 EX and a new EF-M lens...

6176
EOS-M / Re: How do you carry your EOS-M?
« on: July 15, 2013, 02:33:44 PM »
Fits perfectly in my Lowepro Dashpoint 20, which is how I carry it when I'm on the go.

6177
Looking forward to them!

...if they could add master function in the 430ex II replacement, I am definitely in.

Unlikely.  There's no technical reason the 430EX II can't be a master, the control signals for Canon's optical triggering come from the main flash tube, and the 430EX II obviously has one of those.  So expect a replacement 4x0EX flash to be slave only, but able to be triggered by both RF (600EX-RT or ST-E3-RT) or optical masters.

6178
Lenses / Re: Dxo tests canon/nikon/sony 500mm's
« on: July 15, 2013, 11:55:45 AM »
If transmission really was the most important factor then the Sony should  be out scoring the Nikon.  The Sony equals or beats the Nikon in all the listed categories and has  the lowest transmission of the three lenses.

Transmission on macro scale, not micro. In fact, probably not even measured transmission, but rather the specified max aperture. That's why the 50/1.8 lenses outscore the 500/4 lenses.

If you look at the test results they are measuring the combination of lens and body.  Hard to do otherwise.  Makes comparison between manufactures difficult and less than meaningful.

Yes, and sorry, but I think you are missing the point.  For every measurement, all generated with a body attached, the Canon lens comes out on top, in some cases by a significant margin.  Yet, the Score is a tie.  So...the score is fabricated, pulled from their nether orifices, etc.

If you go over to photozone.de's page, they'll quite clearly state that the measurements (or scores) from one camera system (make + sensor size) cannot be compared with another. Given this I can't see why the same wouldn't be true for DxO. What does that mean? That you cannot compare a score of 25 for the Nikon lens with a score of 25 for the Canon or 22 for the Sony lens.

To be able to compare each lens properly would require each lens being mounted on the same camera.

How do they calculate their lens score? Would love to know but I'm pretty sure that it is corporate secret. For the Nikon one to be so high must mean that the readings are somehow weight on the sensor (e.g pixel size.)

The point is that they measure several parameters of optical image quality from the lens, such as sharpness, transmission, distortion, vignetting, and CA.  They could generate a Lens Score based on those parameters, but they don't. Had they done so, the Canon 500/4 II would have soundly trounced the Nikon 500/4. 

For those who argue that it's reasonable that DxO consider the camera in the 'Lens Score', note that the sensor is already factored into the measurements themselves.  P-Mpix measures sharpness of camera + lens, pixel size affects CA, etc.  Even their transmission measurement changes with different cameras.  So by factoring in the camera directly in the measurements (reasonable) then factoring it in again in the overall score where it's given an undisclosed (but evidently very significant) weighting, means their 'Lens Score' is as much if not more a camera score than a lens score.

One more point - considering just their P-Mpix measure of sharpness, by their definition the Nikon 500/4 results in a loss of more that 55% of the resolution of which the D800 sensor is capable, whereas the Canon 500/4 II only decreases the 5DIII's potential resolution by less than 14%.  Of course, the Canon lens also outresolves the Nikon by an absolute assessment, even taking the higher resolution D800 sensor into account.  But they get the same 'Lens Score'. Right.

They should rename their Overall Scores to a Camera Basic Score and a Lens Basic Score, so we could abbreviate them for what they really are: BS.  Actually, that's probably giving them too much credit, because real Bovine Scat makes good fertilizer, whereas DxOMark's BS has no real-world utility.

6179
Last not least, note that if people rave about thin dof they often mean "strong background blur" except if you like the "only the nose in focus" type shots, and same thing here: bokeh also strongly depends on focal length and object/background distance relationship.

Except that bokeh really refers to the quality of the OOF blur, independent of quantity.  But maybe that's a story for another day.  ;)

6180
There's no "story". DOF is a characteristic of a lens and has nothing to do with sensor size. End of story.

You couldn't be more wrong. Perhaps you're stuck in the circle of confusion...   ::)

If you take two pictures at the same position with the same lens on both a crop and a full frame, the distance between the nearest in focus object and the furthest away in focus object will be the same, so the depth of field does not change. Obviously the image captured will be different on each.

However, if you're talking about the depth of field for an equivalent picture, you'd have to move the full frame camera closer which would result in a reduced depth of field.

In the former case, my head shot just became an eyes-and-mouth shot that I had to delete because most people like to see their whole face in a portrait. The latter case is far more relevant to most types of photography. The exception might be macro photography, where at 1:1 magnification, you are at the MFD of the lens, regardless of sensor size.  But at macro distances, DoF is incredibly thin anyway (and the assumptions made by most DoF calculators don't hold).

As for DoF being solely a property of the lens, what, subject distance no longer matters??

The real story is that DoF is determined by subject magnification and lens aperture.

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