April 21, 2014, 02:31:27 AM

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Messages - dilbert

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1
Sorry, I'll shut up now. Bring on the beautiful photos!

Good idea. He is just trying to bait you.

Damn you! There goes my Easter entertainment.

2
When you get into what diffraction actually is, you learn that it is not actually "caused" by anything. Diffraction is an intrinsic trait of light that exists within the wavefront. It is often described as the "bending" of light caused by it's encounter with an obstruction or an opening. That's a useful description to describe the effect of what is happening, however sadly it is not actually an accurate description of what is actually causing the effect.


Diffraction happens with waves and one method that we use to model light's behaviour is to say that in some circumstances it behaves like a wave. Diffraction is not an intrinsic property of light at all, it is a trait of waves and how waves behave.

Please stop spreading bad science.


I'm sorry, but I beg to differ. Here is an article that details the actual science of what a diffracted wavefront is, how diffraction in a wavefront presents and behaves, :

http://www.telescope-optics.net/wave.htm
...


You don't know what you don't know and you're just using a random web article that happens to provide a theory that makes sense to you.

Answering your questions is beyond my ability, schooling or training.

Go find a course on physics that teaches about light and learn about it the way professionals do. An astronomer does not learn about physics from the web. Articles on the web greatly simplify things.


LOL  :o  ???

That isn't a random web site. I found that site years ago (probably before I ever even started posting on these forums) while researching optics for photography (I think that would make it even my pre-DSLR days, as I like to research concepts, theory, equipment, brands, etc. before I buy anything.) I pulled that site out of my bookmarks, bookmarks that I've been stringing along from Opera version to Opera version for years.

It's one of the best web sites on the net that covers this stuff in as detailed, specific, mathematic, and scientific a manner as you can find, too! I seriously challenge you to find a better resource than that that explains the concepts better, or more correctly. And it is FAR from "simplified". Did you even check it out, did you actually look through the site at all? Do you know how much science and mathematics is used in that site to explain the concepts of optics, refraction, reflection, diffraction, and every other aspect of telescopes? It's riddled with math and complex theories, the same exact theories I LEARNED IN MY PHYSICS CLASSES IN COLLEGE.

My knowledge doesn't come only from the web...the web is simply an easy source for reference when one is trying to back up their arguments with hard facts (something I have done plenty...I still don't see any references from you to back up anything your saying.) I've got my old college physics books on my bookshelf here, right alongside, um, oh yeah, Feynman's QED (fantastic book, that.) I also have Newton's "Optiks" on the same shelf, as a nostalgic historical reference and read.

I guess I should have expected you to try and refute hard science. I do challenge you to actually read the site, instead of simply assuming it is unscientific or otherwise flawed simply because I'm the one who posted the link. You might actually learn something, find it edifying.


If all of what you say is true then you would not have said that diffraction was an intrinsic property of light.

The website presents formulas and theory for light relating to telescopes. In that regard it is useful for photographers because telescopes are very much like lenses (well some telescopes are.)

If you'd really learnt physics in college and studied it and learnt about light then you'd know what isn't on that website without needing me to search it for you.

Note that I haven't said anything on this topic that disagrees with hard science - I believe that it is you now putting words in my mouth. What I have said is that you should go to college and do a course on physics and learn about light. Or maybe in your case it would be "go back to college and repeat" as the first time around it obviously never sunk in.

Maybe you should go and read those old physics books and tell us what they say about light rather than what a web page says. Or do those books date back to the 1800s? Anyway it doesn't matter as I don't really care what's on your bookshelves. It is however sad that you appear to no longer know how to use the resources on your bookshelves and only know how to use those on  the Internet. Which is a shame and a pity.

3
Third Party Manufacturers / Re: Zeiss Otus Initial Impressions
« on: April 20, 2014, 09:38:08 PM »
When you get into what diffraction actually is, you learn that it is not actually "caused" by anything. Diffraction is an intrinsic trait of light that exists within the wavefront. It is often described as the "bending" of light caused by it's encounter with an obstruction or an opening. That's a useful description to describe the effect of what is happening, however sadly it is not actually an accurate description of what is actually causing the effect.


Diffraction happens with waves and one method that we use to model light's behaviour is to say that in some circumstances it behaves like a wave. Diffraction is not an intrinsic property of light at all, it is a trait of waves and how waves behave.

Please stop spreading bad science.


I'm sorry, but I beg to differ. Here is an article that details the actual science of what a diffracted wavefront is, how diffraction in a wavefront presents and behaves, :

http://www.telescope-optics.net/wave.htm
...


You don't know what you don't know and you're just using a random web article that happens to provide a theory that makes sense to you.

Answering your questions is beyond my ability, schooling or training.

Go find a course on physics that teaches about light and learn about it the way professionals do. An astronomer does not learn about physics from the web. Articles on the web greatly simplify things.

4
Third Party Manufacturers / Re: Zeiss Otus Initial Impressions
« on: April 20, 2014, 01:29:03 PM »
When you get into what diffraction actually is, you learn that it is not actually "caused" by anything. Diffraction is an intrinsic trait of light that exists within the wavefront. It is often described as the "bending" of light caused by it's encounter with an obstruction or an opening. That's a useful description to describe the effect of what is happening, however sadly it is not actually an accurate description of what is actually causing the effect.

Diffraction happens with waves and one method that we use to model light's behaviour is to say that in some circumstances it behaves like a wave. Diffraction is not an intrinsic property of light at all, it is a trait of waves and how waves behave.

Please stop spreading bad science.

5
Reviews / dpreview.com reviews Sigma 50/f1.4 DG HSM Art
« on: April 20, 2014, 01:12:52 PM »
The latest 50mm is unusually large and expensive for its type; indeed its $950 / £850 price tag suggests Sigma is aiming at users who might otherwise choose the Nikon AF-S Nikkor 58mm F1.4G or Canon EF 50mm F1.2L USM. It bears a distinct family resemblance to the company's 35mm F1.4, but if anything is slightly larger, with a 100mm / 4" long barrel and 77mm filter thread. Its complex optical formula of 13 elements in 8 groups isn't based on a conventional double-Gauss design, like most 50mm primes are, but instead is of the retrofocal type.

http://www.dpreview.com/lensreviews/sigma-50mm-f1-4-dg-hsm

... Camera used: Canon 5D Mark III

6
Software & Accessories / Google Camera App for Depth of Field
« on: April 20, 2014, 08:54:33 AM »
So it would seem that someone (Google!) has taken on the challenge of how do you make a camera phone with limited depth of field produce images that are like that with DSLRs:

http://www.hardwarezone.com.sg/tech-news-googles-new-camera-app-lets-you-add-lens-blur-your-pictures

8
Third Party Manufacturers / Re: Zeiss Otus Initial Impressions
« on: April 20, 2014, 07:47:22 AM »
Not to re-open a closed case, but here's another thought - what happens if you throw a polarizer on the lens?  In theory it should "straighten" the beams of light and eliminate the effects of diffraction, right?

Not necessarily.

If you want to understand light, take a course in physics. Freshman level maybe?

Or get a physics text book ... no, do a course - a good book should be a requirement for the course. Reading CR is not a substitute for doing a course on this if you really want to understand it.
He asked a simple question. If you can´t answer his question or add to it, stay off.

For you I can recommend a book on simple politeness. Freshman level might be to advanced thought ...

He did not ask for a rude reply from an incompetent jerk. Spread your garbage someplace else!

Or, alternatively, start posting images and show us that behind this rude alias, there is one who knows where the view finder on a camera is. I for one have not seen a single image for you, so I believe you haven´t shot a single decent image in your life. So until I see someone comment on your images, you will remain on my list of ignored posters.

So what would you have me do?

Give him a partial answer that is incomplete and doesn't transfer proper knowledge?

Redirect him to a web page that kind of tells him what to expect but doesn't convey full understanding?

Maybe quote one or two web pages and pretend to be an "expert" like others here?

Sometimes the best advice for someone is where to find information or how to obtain it because everything else will not come close. Maybe my recommendation is because I've studied physics and understand that doing a course in it will teach you more and give you a much better understanding of light than any amount of random posts here.

FWIW, I've posted images on this website. If you (or anyone else) really care(s) enough, you'll be able to find them.

9
Third Party Manufacturers / Re: Zeiss Otus Initial Impressions
« on: April 20, 2014, 12:33:29 AM »
Not to re-open a closed case, but here's another thought - what happens if you throw a polarizer on the lens?  In theory it should "straighten" the beams of light and eliminate the effects of diffraction, right?

Not necessarily.

If you want to understand light, take a course in physics. Freshman level maybe?

Or get a physics text book ... no, do a course - a good book should be a requirement for the course. Reading CR is not a substitute for doing a course on this if you really want to understand it.

10
Canon General / Re: "MAP" pricing....How long will it last????
« on: April 20, 2014, 12:18:00 AM »
I too was looking at buying a new DSLR but not now.  I just sold a 40D and T3i in anticipation of snagging a 6D or 5DMK III.

Have you looked into Canon USA's refurbed units with 1 year factory warranty and 20% off MAP?  6Ds are available last time I checked.

Call Canon and ask about they loyalty program.  You send in an old film canon camera that you bought off craigslist for $10 (or I'll sell you one for $10), and they give you 20% off the refurb price.  Not all bodies are available... but I think the mkiii and the 6d are now... but I havne't really checked in a while because I have my body and I hopefully won't be upgrading for many years now.

Loyalty discount is only 10% on the 6D and 5D3. I called a couple months back. They also charge sales tax in all but 4 states I believe.

So if you're in CA, it is refurb - 10% + 8.5% (varying), meaning a whole lot of pain to effectively get the advertised price without tax. Probably easier just to buy from some online ship in NY...

You misunderstood. The refurb price is 20% off of map. Then you get 10% off of the refurb price.

No, I didn't but you seemed to miss the point that once you take into account all of the local sales taxes, the 10% discount disappears pretty quickly to make it a questionable benefit. Do you also have to pay to ship the old camera back to Canon?

11
Canon General / Re: "MAP" pricing....How long will it last????
« on: April 19, 2014, 05:38:39 AM »
I too was looking at buying a new DSLR but not now.  I just sold a 40D and T3i in anticipation of snagging a 6D or 5DMK III.

Have you looked into Canon USA's refurbed units with 1 year factory warranty and 20% off MAP?  6Ds are available last time I checked.

Call Canon and ask about they loyalty program.  You send in an old film canon camera that you bought off craigslist for $10 (or I'll sell you one for $10), and they give you 20% off the refurb price.  Not all bodies are available... but I think the mkiii and the 6d are now... but I havne't really checked in a while because I have my body and I hopefully won't be upgrading for many years now.

Loyalty discount is only 10% on the 6D and 5D3. I called a couple months back. They also charge sales tax in all but 4 states I believe.

So if you're in CA, it is refurb - 10% + 8.5% (varying), meaning a whole lot of pain to effectively get the advertised price without tax. Probably easier just to buy from some online ship in NY...

12
Third Party Manufacturers / Re: Samyang Teases Some New Lenses
« on: April 18, 2014, 02:06:35 PM »
When is someone going to make a wide angle lens (16 - 35 or there abouts) for Canon EF mount that doesn't suck, doesn't cost the earth and has auto-focus?

Tokina makes a 16-28mm F2.8 quite interesting, which costs $629.


The Tokina 16-28/2.8 is an EF-S lens, not EF.


No it isn't. The 11-16/2.8 is EF-S (But mounts on full frame). The 16-28 f2.8 is full frame.


But that has the bulbous front element which means using it with filters is a PITA.

Plus photozone doesn't think much of its optics...

http://www.photozone.de/canon_eos_ff/595-tokina162828eosff

13
Third Party Manufacturers / Re: Samyang Teases Some New Lenses
« on: April 18, 2014, 01:02:54 PM »
When is someone going to make a wide angle lens (16 - 35 or there abouts) for Canon EF mount that doesn't suck, doesn't cost the earth and has auto-focus?
Tokina makes a 16-28mm F2.8 quite interesting, which costs $629.

The Tokina 16-28/2.8 is an EF-S lens, not EF.

14
Third Party Manufacturers / Re: Samyang Teases Some New Lenses
« on: April 18, 2014, 09:53:17 AM »
When is someone going to make a wide angle lens (16 - 35 or there abouts) for Canon EF mount that doesn't suck, doesn't cost the earth and has auto-focus?

15
I'm more interested in a future Sigma 85mm Art 8)

+1

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