Messages

1

Third Party Manufacturers / Re: 135mm f/1.8 DG OS ART Next from Sigma? [CR1]

« on: April 23, 2013, 11:36:27 PM »

Other than the OS (Canon IS), I don't see the sigma being a challenger of any sort.
Who knows, though?

The Canon design is an ancient design with blurry corners and a blurry mid-frame. It's not a top of the line lens. It also has severe issues with purple fringing that's very poorly controlled, and as a long lens , lacking image stabilization means if you're just shooting an event or  you're wasting 1-2 stops of light just to counteract camera shake without making your subject any sharper.

Here's a comparison between the 135mm f/2.0 and a much sharper lens:

http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=458&Camera=453&Sample=0&FLI=0&API=0&LensComp=108&CameraComp=0&FLIComp=0&APIComp=0

f/1.8 also makes a difference is subject isolation, and also reduces noise too.

Everyone was saying that you couldn't improve on the 35mm f/1.4 before and look what happened. The problem is that people assume a "good" lens can't be replaced by something that is earth shatteringly better.

Right because comparing a 7000$ dollar White-tele to a Sub-1000$ lens is a fair comparison. 

Wow really? Ok. Here's a $750 Sigma 105mm Macro lens compared to the $1200 135mm L. That's 2/3rds the price of the Canon 135mm L, it's a cheaper lens that blows the Canon lens out of the water with no hint of blurry corners or a blurry mid frame. And it has Image Stabilization. I think that's more than a fair comparison.

http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=790&Sample=0&FLI=0&API=0&LensComp=108&CameraComp=453&SampleComp=0&FLIComp=0&APIComp=0

All these incessant arguments about "IQ", when most people here will never approach the limits of the lenses they have!

Before anybody is allowed to post a lens IQ, colour, rendering, etc comment they should be forced to go see the conditions they are tested in. Bench tests are so far removed from real world use now most of this stuff is irrelevant. If you are using AF then that will have a far greater affect on the sharpness of your images than pretty much anything, assuming you are using two or three times the focal length as a shutter speed, you are on a very heavy tripod, working at one optimal aperture etc etc.

If you are not printing above 20" regularly, if you are using AF, if you are not using a tripod, if you are shooting in anything less than good contrasty light, if you are not shooting wide open, or stopped down, forget bench test resolution figures, they mean nothing.

Oh, and if you want a real dose of reality, ask yourself how this lady does most of this work with a 5D MkII and a 50 f1.8! http://tamarlevine.com/

P.S. After the debacle of Sigma's incompatibility issues, and more importantly, their refusal to stand behind their products and re-chip every single affected lens, I for one, will never buy a Sigma lens regardless of price, features or perceived value. I had a good friend who laughed at me when I got my 16-35 and 24-70, he said his six Sigma lenses cost less, I still use mine and they are worth pretty much what I paid for them ten years ago, his stopped working on his digital bodies and were scrap.

 So you're saying that nobody will notice 3.5 stops of noise? Because that's what the addition of image stabilization wil give you when shooting an event. You know those indoor things with very low light where especially with a 135mm you have tons of unessesary shutter speed to compensate for camera shake. I guess everyone should just be shooting at iso 4800 instead of 400, because that's what you're saying doesn't matter. There's no difference after all. Yep. None. /sarcasm

2

Third Party Manufacturers / Re: 135mm f/1.8 DG OS ART Next from Sigma? [CR1]

« on: April 23, 2013, 12:27:33 PM »

Other than the OS (Canon IS), I don't see the sigma being a challenger of any sort.
Who knows, though?

The Canon design is an ancient design with blurry corners and a blurry mid-frame. It's not a top of the line lens. It also has severe issues with purple fringing that's very poorly controlled, and as a long lens , lacking image stabilization means if you're just shooting an event or  you're wasting 1-2 stops of light just to counteract camera shake without making your subject any sharper.

Here's a comparison between the 135mm f/2.0 and a much sharper lens:

http://www.the-digital-picture.com/Reviews/ISO-12233-Sample-Crops.aspx?Lens=458&Camera=453&Sample=0&FLI=0&API=0&LensComp=108&CameraComp=0&FLIComp=0&APIComp=0

f/1.8 also makes a difference is subject isolation, and also reduces noise too.

Everyone was saying that you couldn't improve on the 35mm f/1.4 before and look what happened. The problem is that people assume a "good" lens can't be replaced by something that is earth shatteringly better.

3

Third Party Manufacturers / Re: 135mm f/1.8 DG OS ART Next from Sigma? [CR1]

« on: April 22, 2013, 11:01:35 PM »

Canon is totally detached from the market, delivering late and under-performing on critical core lenses.  The management that approved the redundant 24-70 IS F4 should be fired.

M

the f4 is not redundant.
 
it´s half the price of the f2.8 and many user don´t need a wide aperture.

the f4 would make a great landscape lens for me, if only the performance would be more consistent.

Several tests have put the 24-70mm at worse or equal to  the 24-105 averaging overlapping focal lengths. The lens was a bad joke in price and image quality. I have tested both its nowhere near the 24-70mm f/2.8 ii, not even on the same planet. It's not even better than the old 24-70mm ii, it's just mediocre. In fact several people that bought it thought it was better than their 24-105mm then did backto back tests with the 24-105mm and found them to be equal then returned the lens.

4

Third Party Manufacturers / Re: 135mm f/1.8 DG OS ART Next from Sigma? [CR1]

« on: April 21, 2013, 02:12:08 PM »

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<strong>More from Sigma in 2013</strong><br />

We’re told Sigma will announce a 135mm f/1.8 DG OS Art lens sometime in 2013. There could be up to 3 more Art lenses announced this year. We’ve previously heard they would be releasing a 24mm f/1.4 DG Art sometime in 2013.</p>
<p>There has been no mention of an f/2 or faster zoom for full frame cameras.</p>
<p>An update to the 50mm f/1.4 could also be on the horizon.</p>
<p><strong><span style=\"color: #ff0000;\">c</span>r</strong></p>

I've been waiting for this lens for literally years. Sigma is my new favorite company if this is real. Make a 16-35mm f/2.8 OS, and a 24-70mm F/2.8 OS (better than tamron) and a 55mm f/1.4 on par with zeiss and all my lenses will be sigmas!!

Great news!

5

Third Party Manufacturers / Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C

« on: April 20, 2013, 10:35:10 PM »

Just wanted to chime in on the conversion debate.

A 15-35mm f/1.8 lens on crop, will deliver identical optical geometry to a 29-56mm f/2.88lens on full frame.

Depth of field for example, just like angle of view is a function of geometry.



So as the iris or aperture opens up more it allows more light in, but because that light is light that is coming at a higher incident angle it is focused over a greater area if it is behind or infront of the focal plane. So therefore you have a shallower depth of field. See how the red point is larger and therefore will be blurred on the open aperture example?

Here's another example:





People have been misled with crop to full frame conversions  for years.

The "35mm equivalent" is what is really important and nothing else. Your images on 35mm equivalent will always look the same no matter what.

From a physics perspective the "35mm equivalent" is capturing identical information. What really matters is the geometry of the light hitting the sensor, and with 35mm equivalent the geometry will always be the same for a given equivalence. Not only that but your flash settings etc will be identical:

Going back to the 35mm equivalent discussion, consider this:

On APS-C (like the 7D) compared to full frame (like the 5D Mark III)


The sensor is 1.6 x 1.6 times smaller.

35mm equivalent aperture - Multiply F-Number by (1.6 ) . (an f stop is a base 2 log, so even though we have 1.6x1.6 times as much light we take the square root, which is 1.6 to multiply the F number by. (example 2.8 x 1.6 = 4.48, 4.0 x 1.6 = 6.4, 1.8 x 1.6 = 2.88))

35mm equivalent focal length - Multiply by 1.6

35mm equivalent ISO or light sensitivity - Multiply by (1.6 x 1.6) (bet you haven't heard of that,  but if you do the math the an APS-C sensor amplifies the signal 1.6x1.6 times more at a given PIXEL than the a full frame camera, so even if both say ISO 800, ISO 800 on the an APS-C  it is multiplying the light from each individual pixel the same as ISO 2000 full frame, assuming they had identical resolution.

This is an important point of contention. So while for a given area of a light sensetive material, ISO provides a set level of amplification, cameras do not have a consistent area that they absorb incoming light on. Some have finger nail sized sesnors, and some postage stamp sized sensors. What's more important to consider is each individual pixel and it's level of amplification. Images are formed from pixels, so to acheive a true equivalency between different sized sensors and produce identical images we must consider the data collected at each individual pixel.

Simply put APS-C cameras have more dense sensors with more pixels, even with identical resolution. Because ISO is dependent on a given volume of light passing through a given area, if we increase the number of pixels in that area each pixel will have a stronger amplification level.

To illustrate this imagine a rain storm. On one part of the ground you have a set of square buckets that are 1" x 1" x 10", on another you have a set of buckets that are 2" x 2" x 10". After a given identical volume of rain, the 2x2x10 buckets will have 4 times more liquid in them than the 1x1x10 buckets. However four 1x1x10 buckets will have the same amount of rain in them as a single 2x2x10 bucket, as they will cover the same area (4 square inches).

Now lets imagine you have to create a given level of brightness from the amount of liquid in each bucket. Because the smaller buckets have a smaller cross section you have to multiply the amount of liquid in them for each smaller bucket to produce the same level of brightness as a larger bucket.

So on the 2x2x10 bucket, 20 cubic inches of rain might equal a luminance value of 128. For the same amount of rain fall each 1x1x10 bucket would only contain 5 cubic inches of rain, but if you wanted to have the same luminance value you would have to multiply the volume of light at each pixel by 4.

In this way, a sensor with denser pixels always has to multiply the volume of light to get a given luminance value more than a sensor that is less dense.

ISO is a function of the volume of light resulting in a certain exposure ie the amount of rain coming from the sky, resulting in a given exposure level. Say 5 inches of rain per hour resulting in a luminance value of 255, and 2.5 inches resulting in 128 in our example.

So to collect identical information ie number of photons at each individual pixel, with an APS-C and FF camera that have identical resolutions, we must use a different volumes of light hitting the sensor, specifically on APS-C we must have a higher volume of light, which results in a lower ISO to produce the same level of exposure. Just like we would have to use a greater flow of rain to collect the same amount of water in a smaller bucket compared to a bigger bucket.

Because light can simply be compressed and expanded at will by changing the beam path, which alters the volume of light in a given area (think magnifying glass), all that we have to do when converting an incoming image from FF to APS-C is focus the same image coming through an identical iris on a smaller area to capture the same exact information on an APS-C sensor as a full frame sensor. If you go through the geometry and the math of doing this equivalency something amazing happens though. At "35mm equivalent" ISO, focal length and aperture and the same shutter speed, on a full frame and APS-C sensor if you have a theoretically perfect body and lens system you would get the exact same photons which came from the exact same sources from your subject landing in the same number and location in each individual coresponding pixel site and resulting in the exact same luminance values in the output for both cameras. With each camera having a different ISO setting, focal length, and aperture.

Identical photons from identical sources, landing in coresponding pixels, resulting in identical luminance values are what is important when desiring to create identical images. That is how 35mm equivalence works, and why it is important.

Discussing anything other than 35mm equivalent values for cameras is like saying I have a million dollars, and then failing to mention these are Zimbabwe dollars worth $20 not, American dollars.

Yes aperture ISO and focal length are fixed numbers, but so are monetary figures, and the most important thing even the most basic dealing of currency has is WHAT currency you're dealing with, and 99% of people require an "equivalent" frame of refference to understand foreign currency or need to do a conversion. Likewise with cameras, geometry (type of currency) is the most important thing when dealing with the performance of a camera system, and the first thing anyone needs to do is bring up a conversion to the local frame of reference, APS-C ,35mm, whatever.

So in other words theoretically a Crop set to:

#1. 17mm - f/2.8 - ISO 800 - 1/50th - with 1/4 flash
#2. 55mm - f/2.8 - ISO 800 - 1/50th - with 1/2 flash

Will produce a 100% identical image with no difference in exposure, lighting, depth of field, field of view or composition when compared to a full frame set to:

#1. 27mm - f/4.48 - ISO 2048 - 1/50th - with 1/4 flash
#2. 88mm - f/4.48 - ISO 2048 - 1/50th - with 1/2 flash

Literally no difference.

Now of course each lens will have it's own characteristics and each body will likewise have it's own, and the full frame bodies and lenses tend to produce higher quality images due to the fact that miaturizing the system has adverse side effects, but if both bodies and lenses were theoretically perfect and had the same resolution these settings would deliver the exact same images with completely identical pixels.

Hope that cleared things up.

6

Third Party Manufacturers / Re: Sigma Announces 18-35 f/1.8 DC HSM Art for APS-C

« on: April 19, 2013, 11:34:01 PM »

I can just imagine Canon & Nikon engineers staring at their screens in disbelief. Sigma engineers have managed to crack some code to lens making. I have the Sigma 35mm f/1.4, just tested the new Sigma 30mm f/1.4 and can't wait for this. Amazing lenses Sigma, now please give me a nice 50mm lens because I am not at all happy with my Canon 50mm. At least my Canon 85mm is great.

It's actually not difficult to make a lens like this any more than it is to make a 24-70mm f/2.8 lens for full frame.

Both will gather approximatly the same amount of light.

The amazing thing here is that Sigma has the motivation to make a lens like this. Canon have been sitting on their butts making ridiculous products for the recent past. T5i? WTF. 8-15mm L fisheye WTF?

Canon have dozens lenses that are 13 years old and a complete embarassment. I think Sigma just saw a moment of weakness and decided to obliterate the competition with these new products.

7

EOS Bodies - For Stills / Re: What made you choose Canon in the first place?

« on: April 13, 2013, 02:00:46 AM »

I picked up a Nikon 5100 and I actually kind of liked it. But then I thought to myself, why pay the same money for a Nikon that was not even made in Japan? So I went for Canon and got a 60D. Stupid reason I know.  3/4 of my friends shoot Nikon. I don't like to be asked to lend lenses. That's another reason. 

Sometimes I wonder if it was the right decision. I have a 6D now. Nikon D600 seems pretty attractive. I'm not going to switch over to Nikon. The switching cost would be too high. But are there things about Canon camera, lenses, or optical technology that are superior to Nikon? I'm not really looking for validation, but I'm curious to learn more about Canon since I consider myself a newbie. Please share your views.

There are really only two things that made me go with Canon.

After a careful review of Canon's lenses and bodies and my shooting needs I figured out that what I needed most was high ISO performance and the best normal lens money can buy.

The 24-70mm f/2.8 II is the best normal lens money can buy and the 5D Mark III has the best high ISO performance, beating the D800 by a slim margin (most sources say they perform equally but the 5D3's rated ISO is actually a quarter of a stop higher, also the noise from the 5D3 has a better more gausian distribution which responds better to NR).

I also get to play with a D600 often, it has several software features removed from the D800 to differentiate it which I didn't like, and the D800 has too many megapixels, and no sRAW mode which means the files will always be huge.

The fact that the 24-70mm f/2.8 II was APO sealed the deal for me.

Right now Canon only has me by a hair.

My hope is that Canon release the following lenses pretty soon to start taking away the lead from other manufacturers in other areas:

35mm 1.4 L II
50mm f/1.8 IS
55mm 1.4 L (based on the Zeiss 55mm f/1.4)
16-35mm f2.8 IS L, based on the Nikon patent, much better IQ.
75-150mm f/2.0 IS L
24-70mm f/2.8 IS

8

PowerShot / Re: SX50 outperforming 5DIII +100-400mm

« on: April 13, 2013, 12:33:31 AM »

So please explain how that is "outperforming" it?

Simply, the detail or resolution from the SX50 at 1200mm is better than the 5DIII +100-400mm at 400mm. If you take a crop from the 5DIII combo to give the same view as the SX50, the SX50 image is better. This is useful if you are taking a bird photo which requires heavy cropping from the 5DIII and 6x less from the SX50.

As I had in the first post, I am not implying the SX50 is better than the 5DIII but the extra reach at 1200mm beats out the 100-400mm at 400mm. That is quite remarkable and unexpected to me, and it means I can travel light. Normally, I would use the Canon 5DIII with a 600mm prime, and only use the 100-400mm when I had to travel with limited luggage. But, for work trips I'll just take the SX50 for from now on knowing I can get some spectacular shots.

So you're taking a crop where only 1 pixel out of every 9 on the 5D Mark III is thrown out, and you're saying that a point and shoot is better.

This would require your 5D Mark III to have 10 TIMES the starting resolution to get a better result.

No wonder you came to the conclusion you did. Now try the 5D Mark III with a 2x teleconverter and a 400mm lens vs the SX50 @ 800mm.

9

Third Party Manufacturers / Re: The Blackmagic Production Camera 4K

« on: April 11, 2013, 09:56:55 PM »

The Blackmagic Design cameras are pretty awesome for what they are and how they've burst onto the video market, but for us Windows-based PC owners without a brand new Thunderbolt input device, they're useless. I don't even think that a stand-alone SSD reader exists, so that puts the kibosh on my interest. As if I have the cash-ola to spend anyways! 

Ummm there are 427 "stand-alone SSD readers" available on Newegg alone, and 19,349 available on Amazon (that's ninteen thousand). Here's one I recommend (mid range) for $24.

http://www.newegg.com/Product/Product.aspx?Item=N82E16817153066

Or one of the fastest ones you can get for $45:

http://www.newegg.com/Product/Product.aspx?Item=N82E16817153133


Stand alone SSD readers second only to SD card readers in popularity.

10

Third Party Manufacturers / Re: The Blackmagic Production Camera 4K

« on: April 10, 2013, 02:31:56 AM »

Bravo to BlackMagic for showing the big boys how it's done. This is the company that RED Digital Cinema should have been but alas they've become just like all the rest.

Is it possible that they underestimated how expensive it is to innovate?
We have all had conversations about "how cheap the parts for gear are and how come someone doesn't put it together and show the big boys"
When the real world intrudes one finds things are priced where they are for a reason.

Bodies are easy to make, lenses are the hard part.

The problem with Canon is that they jerk their customers around too much with bodies. 18 MP on APS-C for what 4-5 years now? No 4k video on a professional DSLR like the 5D Mark III or the 1DX?

Canon is well known to drag it's feet with innovation, they have lenses and bodies that all their competitors from Zeiss, to Nikon to Sigma to Tamron have positivly nuked.

The 35mm Sigma has 2.5 stops better resolution that the 35mm Canon.

The 50mm Zeiss has 5 stops better resolution than the Canon 50mm 1.4 or 50mm 1.2L.

The Nikon 80-400mm has a 5 stop resolution advantage over the ridiculously old Canon 100-400mm.

The Nikon D800 nukes Canon in the megapixel department, the Sony NEX melts face off the Canon EOS M in every dimension.

How about the 14-24mm f/2.8 too?

Now the Black Magic cameras has mostly demolish Canon's video cameras. Not having RAW video is like not having RAW in photography. Canon's 1DC doesn't do raw video, and neither does Canon's c100 or c300 so for video those are the dinky point and shoots and nowhere near the quality of this camera. Canon's primary serious entry into video is their $25,000 c500, and that camera isn't full frame, it's super 35mm just like the Black Magic 4k. So BMC just released a $4,000 camera that goes toe to toe (and probably beats) Canon's $25,000 camera, which amounts to making the whole Canon cinema line up obsolete.

In fact the only reasons why Canon is still relevant are the 24-70mm f/2.8 II and the 5D Mark III, their supertelephotos and tilt shift lenses.

Don't get me wrong I used to be a huge fan of Canon and loved them and constantly sang their praises... when they actually had innovative products. Now they are just a creaky old rotting corpse that releases overpriced products that are obsolete before they hit shelves. T5i anyone?

Their only saving grace for innovation is the fact that Sigma and Tamron make lenses for them.

Canon is an embarassment and they deserve it for sitting around and developing ridiculous products like the 70-300mm DO, touch screen DSLR's, t5i, a zooming fish eye to cover APS-C and full frame in one lens (wow), their cinema lenses which are L lenses with slight modifications and 3 times the price. 1DC which is just a modified 1DX for twice the price (why did the 1DX not include all the 1DC features?), worthless EOS M that autofocuses like a joke, 18mp sensor with terrible focusing abbility in video mode (no pro video guys even use autofocus).

Canon needs to learn that one thing sells cameras. Good core products that push the bleeding edge of technology. Canon has paid zero attention to their core products in the last 3 years. Even their best body and lens the 5D Mark III and 24-70mm II were both afterthoughts. The 5D Mark III was finished a year before it was released and Canon sat on it, to milk people on 5D Mark II inventory according to official sources, and the 24-70mm II was ONLY released for no other reason than to stop constant 24-70mm I warranty claims due to copy variation and extreme decentering.

Canon's attention to it's core products has been a joke. The only semi decent core product they released in recent memory was the 1DX and then that was gimped so they could sell more cinema products which were obsolete months after they hit shelves with products like the Black Magic cameras.

Canon's product development is a sad mismanaged joke and the writing on the wall is getting ever clearer, especially combined with their new ultra greedy pricing designed to alienate customers.

11

EOS Bodies - For Stills / Re: 7D vs 5D3 noise @ ISO400

« on: March 31, 2013, 05:17:05 PM »

ISO 400 on the 7D and 5D3 are completely different sensetivity levels and it's misleading to directly compare them.

Cameras are a function of geometry.

People have been misled with crop to full frame conversions  for years.

The 5D3 was my first FF camera body.  I previously used crops... 20D and 40D.  As stated, I am evaluating either a 7D or 5D2 as a backup to the 5D3.

I am not a physics major and thus, I am not going to dispute Radiating's calculations and references to physics.  I understand that it isn't a 1:1 comparison, but...

What I do know is that a photon of light is still the same size regardless of sensor and that a crop sensor 'extrapolates' the equivalent pixel dimensions due to the fact that pixel density is so great and thus pixel size is so small, that is is practically splitting a single photon of light.

I also know that at the end of the day, if any of us were to print either OOC image to their largest extent @ 300 dpi, that we would see the difference between the 7D and the 5D3 as seen clearly by these 100% crops and therefore, the reality is that a crop body's sensor is simply inferior.

Desiring to hold on to the 'reach' (cringe) benefits of APS-C, I wanted very much to keep the 7D as an all-around versatile camera and as a backup to the 5D3.  After the pictures I took today, and the grain I see in them even at 50% (heck, even looking at the entire image sized to fit on a 15" laptop display) there is clearly an improvement in IQ from a FF body.

After evaluating the 7D, it's clear an APS-C is inferior.  It's just the reality of physics.  We can't shrink light any further, but we are trying to over-resolve it.  Here come the arrows and darts...

See that's where your wrong, the 7D isn't working with less light because it has a smaller sensor, and it's getting nowhere near splitting photons. This isn't the issue. The amount of noise you get in an image is based on the amount of light being emitted by the object. Noise (for the most post) is a result of the quantum properties of light in that light exists as a gausian distribution of photons, light isn't emitted uniformly but photons hit an object at random. The difference in light and dark areas in an image resulting from noise are caused therefore because in the light area you had 16 photons and in the dark area you had say 9. Because of random probabily the light from your subject doesn't arrive at a uniform time. Overall the random noise will average out so if you leave the shutter open for twice as long you might get 25 photons in the light area, and say 26 in the dark area of two pixels. The reason different cameras have different noise levels is because for the most part cameras throw away some of the photons because the whole surface of a sensor doesn't absorb light, and some of the light is absorbed by the micro lenses and bayer dye. Then on top of that cameras introduce a slight amount of electrical noise (though electrical noise can be a big issue in astro photography).

For the most part though noise comes from the subject, and the difference between noise comes from the amount of light the camera throws away.

Though the 5D3 does throw away less noise and introduce less electrical noise than the 7D. (5D3 throws away 51% of light, 7D throws away 59%)

Anyways like I said

So in other words theoretically a Crop set to:

#1. 17mm - f/2.8 - ISO 800 - 1/50th - with 1/4 flash
#2. 55mm - f/2.8 - ISO 800 - 1/50th - with 1/2 flash

Will produce a 100% identical image with no difference in exposure, lighting, depth of field, field of view or composition when compared to a full frame set to:

#1. 27mm - f/4.48 - ISO 2048 - 1/50th - with 1/4 flash
#2. 88mm - f/4.48 - ISO 2048 - 1/50th - with 1/2 flash

Literally no difference.

What I mean by this is you would technically capture even the exact same photons.


To photograph something clearly part of the light coming from the object must be ignored because when light hits an object it is scattered in all directions. To see the details of an object clearly, you have to selectivly remove the light which isn't paralell to the line of sight between you and the object. Otherwise the image will be blurry.

To accomplish this all that is needed is an aperture, or something that blocks the path of the light which blurs blur your image. The thing is that the sensor size is part of the aperture too in that it removes light that is less parallel to the line of sight.



This is why when you use a 1.4x teleconverter it projects an image circle that is greater than your sensor size, and it therefore reports the lens as having an aperture 1 stop lower, because the lens allows light which is less parallel to the line of sight to make it onto the captured image circle. We measure aperture values from the lens' perspective and ignore the camera though which is why this is confusing.

Full frame lenses on crop simply project an image circle that is greater than the sensor and so they are always fundamentally stopped down a little. To compensate the light is multiplied in intensity so our exposure calculations aren't off, so a given sensor sensetivity is labled ISO 2048 on full frame but is labled ISO 800 on crop instead of labling aperture f/2.8 aperture f/4.48. By using a 1.6 teleconverter or 1.6 crop camera with a theoretically perfect lens at a 35mm equivalent: aperture, ISO and focal length you will be ignoring the exact same photons as you would on full frame and you will literally be collecting the exact same photons, and if we use a theoretically perfect camera, you would get the exact same image photon for photon, pixel for pixel. Light doesn't care how dense it is because light is 99.99999999999% empty space, all that matters is bending the optical path correctly to capture the nessesary photons.

The problem we run into of course is just that the manufacturers don't make lenses that can bend a crop camera's photons the way we want. There's no 17-55mm f/1.8 lens. And the reason why full frame is better is because when you're bending the optical path on a crop camera it has to be more precisely done for a given resolution, so with a given level of precision in the manufacturing process, particularly our abbility to polish and assemble the lenses precisely, full frame lenses will have more resolution due to magnifying the flaws in our manufacturing process less. Likewise medium format cameras magnify the flaws in the manufacturing process even less so we have even better lens resolution from them.

Crop cameras currently have slightly worse sensors too. As I mentioned the 5D3 absorbs 20% more light than the 7D and it's electronics introduce less noise for a cleaner result. Overall we're talking a half stop or more at euqivalent aperture and ISO.


With that said the 7D also can't be stopped down as far, it would have to shoot at ISO 19 to get an image with as little noise as a 5D3 at "low" ISO.

So on crop you have worse sensors, worse ISO ranges, worse lens resolution, and they don't make fast enough lenses for crop cameras like 17-55mm f/1.8 lenses.

On the other hand some will argue they don't make long enough lenses for full frame, so crop is better for reach, especially compared to teleconverting, as you will have a theoretically perfect teleconverter with better autofocus.

12

EOS Bodies - For Stills / Re: 7D vs 5D3 noise @ ISO400

« on: March 30, 2013, 10:32:32 PM »

ISO 400 on the 7D and 5D3 are completely different sensetivity levels and it's misleading to directly compare them.

Cameras are a function of geometry.

People have been misled with crop to full frame conversions  for years.

The "35mm equivalent" is what is really important and nothing else. Your images on 35mm equivalent will always look the same no matter what.

From a physics perspective the "35mm equivalent" is capturing identical information. What really matters is the geometry of the light hitting the sensor, and with 35mm equivalent the geometry will always be the same for a given equivalence. Not only that but your flash settings etc will be identical:

On 7D compared the the 5D Mark III


The sensor is 1.6 x 1.6 times smaller.

35mm equivalent aperture - Multiply F-Number by (1.6 ) . (an f stop is a base 2 log, so even though we have 1.6x1.6 times as much light we take the square root, which is 1.6 to multiply the F number by. (example 2.8 x 1.6 = 4.48, 4.0 x 1.6 = 6.4))

35mm equivalent focal length - Multiply by 1.6

35mm equivalent ISO or light sensitivity - Multiply by (1.6 x 1.6) (bet you haven't heard of that,  but if you do the math the 7D's sensor amplifies the signal 1.6x1.6 times more at a given ISO than the 5D3, so even if both say ISO 800, ISO 800 on the 7D  is multiplying the pixels the same as ISO 2000 on the 5D Mark III)

It's like saying:

I have a million dollars, and then failing to mention these are Zimbabwe dollars worth $20 not, American dollars.

Yes aperture ISO and focal length are fixed numbers, but so are monetary figures, and the most important thing even the most basic dealing of currency has is WHAT currency you're dealing with, and 99% of people require an "equivalent" frame of refference to understand foreign currency or need to do a conversion. Likewise with cameras, geometry (type of currency) is the most important thing when dealing with the performance of a camera system, and the first thing anyone needs to do is bring up a conversion to the local frame of reference.


So it is misleading to compare the 7D vs 5D3 at equal ISO because for a given depth of field they will have different apertures


So in other words theoretically a Crop set to:

#1. 17mm - f/2.8 - ISO 800 - 1/50th - with 1/4 flash
#2. 55mm - f/2.8 - ISO 800 - 1/50th - with 1/2 flash

Will produce a 100% identical image with no difference in exposure, lighting, depth of field, field of view or composition when compared to a full frame set to:

#1. 27mm - f/4.48 - ISO 2048 - 1/50th - with 1/4 flash
#2. 88mm - f/4.48 - ISO 2048 - 1/50th - with 1/2 flash

Literally no difference.

Now of course each lens will have it's own characteristics and each body will likewise have it's own, and full frame lenses will delivery much better image quality than crop typically as will any full frame body, but if both bodies and lenses were theoretically perfect and had the same resolution these settings would deliver the exact same with completely identical pixels.

Hope that helps.

13

EOS Bodies - For Stills / Re: Bias of tests

« on: March 30, 2013, 06:23:38 PM »

Maybe you will be  your eyes, but does anybody know, how the test-magazines (online, printed) get their cameras for testing?
Are these Cameras "specially improved" by the manufacturers? Or do test magazines get "normal" cameras from the production lines?

Most review sites buy their equipment or borrow it through normal market chanels. This is one of the reason why reviews tend to be so uneven and contradictory, copies of certain Canon lenses can have as much as 30% variation in performance. That's thirty percent.

14

Lenses / Re: Prime vs zoom

« on: March 26, 2013, 01:30:28 AM »

Having the trinity for both zooms and primes is the way to go, if you can. 
Zooms for versatility and convenience, and fast primes to get those magical shots.

Agree 100%

though I do

2.8 & 1.4 trinity

15

EOS Bodies / Re: 6D Autofocus not impressive

« on: March 25, 2013, 11:20:34 PM »

I rented a 6D camera body to take helicopter skiing in Canada. I brought my 24-105 f/4, 40 f/2.8, and my 50 f/1.8 lenses. I found the autofocus to be slow with all 3 lenses, especially in lower light. I really experimented by changing many of the autofocus parameters and resetting the rental body to factory settings to make sure nothing was amiss. I found the 6D autofocus to be for the most part as good as my Rebel 550D with each of my lenses. I was really disappointed because a want a new body to replace my Rebel.  Lensrentals.com checked the 6D and found it up to factory specs.  Looks like I may have to pony up for the 5D m III.  Does anyone think the climate and elevation had anything to do with the slow AF?  Or does the 6D really have a mediocre AF?

The 6D has nearly the exact same autofocus system as a newer Rebel so it's no surprise at all that it performed similarly.  If you want better autofocus get a 5D3 or a 1DX, the purpose of the 6D is improved image quality and sensor size.