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fldspringer Mar 5, 2007 2:32 PM

The 4/3 image circle is about 400 cubic milimeters. The 4/3 sensor is 243 cubic milimeters. That's about 60% of the light falls on the sensor.

Canon's APS-C sensor is 384 cubic milimeters. The 35mm film image circle is roughly 1475 cubic milimeters. Thats roughly 25% of the light actually falls on the sensor. Hmmm!

Another part of 4/3 lens design is that light should hit the sensor at almost 90 degree angles. 35mm film was sensitive to any light from any angle. The lenses were designed for the film. Canon's position is that lenses designed for film are actually ideal for full frame sensors, which also happens to be ideal for their 1.3x sensors AND they just so happen to be ideal for their 1.6x sensors. They must have some really great engineers to make that happen.

Sigma makes some lenses fit the 4/3 mount, including three from your list. I count eleven in all. Of those eleven, at least six are slapping coating on the back element of a 35mm lens and calling it good. They not a true digital lens. If I EVER decided to purchase one of these lenses, it would be with my eyes wide open as to performance issues. To Sigma's credit, they are building fresh designs specifically for digital. Some (maybe all) are available for the 4/3 mount.

Acording to my calculations, slightly more than 1 stop of light is lost off sensor using full frame lenses rather than a lens designed to project the image circle specifically forthe small Canon sensor. The light also is not normal to the sensor at the edges. But hey. There IS 60 choices of these lenses available.

Sure there are some areas where there are few or no good choices. Just like Canon and Nikon have no choices for nearly all the Olympus top pro lens line. Physics are physics and the lens selection for Olympus' cameras are its greatest strength. The GREATEST selection of lenses designed for digital use.

Perhaps you would like the choice to say yes or no to the poor lenses. How many customers have thrown money away for absolute trash. The things SHOULD carry warning labels "not for digital use" and some should also say "not recommended for film use either".

Perhaps you would be better to let it die.

kenbalbari Mar 5, 2007 2:38 PM

"I concede that Canon has a few clunkers in its line-up, but to say that nothing Canon has for less than $1,000 is worth buying is a gross exageration. The Canon EF 50mm f/1.8 II is a fine lens, and it is available for $70! The Canon EF 70-300mm f/4-5.6 IS USM AF, EF-S 10-22mm f/3.5-4.5 USM, Canon EF-S 17-85mm f4-5.6 IS USM are just a few fine Canon lenses available for less than $1,000."

I actually agree here on all points. The IS lenses there are good, not great optically, and don't appeal to me as much, but for some the IS is worth paying quite a bit extra for. But Canon can make those "affordable" because the IS costs very little to add relative to what they are charging for it. Two others are two of the four the EF-S zoom lenses Canon does have, which I've been saying they ought to make more of.

I never said Canon didn't have good options there. I initially said Canon was more flexible, mentioned a couple times it's superiority in low light conditions, questioned the trusted reviews site which suggested no noise problem for the E-400 (it's really about a stop worse than the XTi) and emphasized the importance of fast prime lenses for low light shooting, and the more limited options for Olympus there compared to Canon.

I took issue when John suggested a huge deal of disparity beyond that, saying:

"There are still more good options with Canon than Olympus for many purposes. But it's not near the difference the raw number of lenses available suggests. "

I did not say ther were no good options under $1000. When it comes to zoom lenses under $1000, in the range suggested by DigiGal (up to 300mm equivalent) I personally would give an edge to Olympus, for my needs. But it's certainly close enough that I wouldn't hesitate to buy the Canon if I liked the camera better.

So perhaps we should end this hijacking and return this thread to it's rightful owner?

[Though inn the interest of accuracy, John, three of those Sigma lenses are currently available for four-thirds - the 50-500, 105mm macro, and 150mm macro]

I believe Digigal mentioned an interest in portraiture? I happen to be a fan of the Canon 50mm f1.4, Olympus 50mm f2.0, Pentax 50mm f1.4, Pentax 40mm f2.8 Limited, Pentax 77mm f1.8 Limited, Tamron 90mm f2.8, and the Nikon 85mm f1.8. Some might consider some of these a bit long for digital (at least indoors), but I like waist up and head and shoulder shots.

I even like some telezooms for portraiture, though more outdoors, like the Canon 70-200 f4L, Olympus 50-200 f2.8-3.5, Nikon 80-200 f2.8, and Sigma 70-200 f2.8.

I would suggest to DigiGal, if she is uncertain about the capabilities of any of the cameras or lenses she might be considering, she take a look at what results real world everyday users are getting for the type of photography she is considering.

The pbase allows searches by camera or lens. The flickr site has a new feature where you can search by camera and select a type of photography (like portaiture or sports).

After all, it's much more fun looking at nice pictures than reading through reviews, arguments or technical specifications. And probably at least as useful. (and p.s. If you see something you like, be sure to click view EXIF data to see the deails of how it was shot).

JohnG Mar 5, 2007 2:39 PM

fldspringer wrote:

Acording to my calculations, slightly more than 1 stop of light is lost off sensor using full frame lenses rather than a lens designed to project the image circle specifically forthe small Canon sensor. The light also is not normal to the sensor at the edges. But hey. There IS 60 choices of these lenses available.

I'm sorry - I don't follow this point - how are you losing a stop of light? Of course you're right, all the pro wildlife photogs and sports photogs using 600mm, 400mm, 300mm primes and the Canon 70-200 2.8 lens (all on crop cameras - only in this case 1.3 crop cameras)will be glad to know their lenses ae inferior. I'm sure they'll be glad you clarified that for them and let them know that full frame lenses are useless on a crop camera. But, back to your statment: of the image circle still captured, how is it losing a stop of light. For example, take an image circle from a 70-200 2.8 lens at 2.8. Are you saying the image captured is really like an aperture of 4.0? I just want to understand the argument clearly. By the way, so I keep my facts strait - which of the sigma lenses I mentionedwere currently being offered in an olympus mount?

fldspringer Mar 5, 2007 3:19 PM

105mm f2.8

150mm f2.8

50-500mm bigma

The top pro lenses are f2.0 across the entire range for the 14-35 (new) and 35-100. Canon and Nikon have nothing that bright in any zoom. They also have a 150mm f2 that has the reach after the 2x factor of a 300mm f2. They have a 90-250 f2.8 (reach 180-500 in 35mm terms). They have a 300mm f2.8 that reaches 600mm. Neither Canon or Nikon can reach that far that bright that I know of. I could be wrong. Tell me their options. Anyway, that is what I mean by saying they don't have an answer to that line of lenses.

As to the light loss. I can't tell you that the manufacturers aren't moving the sensor closer to the lens as mirror clearance and focal range allows. I can tell you that that would cause a smaller image circle, but it also means the light isn't normal (90 degrees) to the sensor. If you have a film camera perhaps you can measure it. If the measure is the same, the loss is there. But what I am saying is that digital lens design is better for digital photography. Period! If Canon and Nikon would do a digital redesign, the performance would increase. They instead chose a legacy path and kept the film lenses as part of that marketing strategy.

kenbalbari Mar 5, 2007 3:46 PM

"I'm sorry - I don't follow this point - how are you losing a stop of light? "

I didn't quite agree there either. But perhaps we should start another thread if we want to get into this technical debate? Much as I like to get into this stuff sometimes, I think DigiGal has maybe had enough of it. After all, she was hoping to buy a camera, not build one.

But, I might argue that the aditional cost of building the larger lens ultimately means that you often end up with a higher maximum aperture in a lens of the same price. So in at least some cases you have a good Canon f4 at the price of a Zuiko f2.8-3.5. And, the Olympus also has the same depth of field at f2.8 as you would at f3.5 on the Canon. But that only goes so far. It applies to some of the zoom range, but on the prime end, you still have f1.4 primes for Canon, Nikon , and Pentax. And no 1.0 primes for the four-thirds to match them with a stop less ISO.

Also, if you simply compare the sharpness of the Zuiko glass, it very impressive in resolving lines per millimeter. But, the sensor is ultimately part of the resolution picture as well. You need the lens to be 25% sharper to get the same lines widths per picture height. Agaisnt the cheaper glass the Zuikos accomplish that nicely. But at a certain point, with quality glass on the Canon, you are going to get higher resolutions than the smaller sensor is capable of.

In the end, you are talking about two different formats here (though very close), and the typical tradeoffs involved there. It's like arguing the merits of 645 (6x4.5cm) vs. 6x7 (obviously 6x7cm) in medium format film. It's not that one is better than the other. Choose the most efficient tool for the job.

The smaller format always tends to offer some advantges in size, convenience, and cost. The larger format always ultimately will provide higher potential quality for more demanding purposes (provided you properly use quality equipment).

JohnG Mar 5, 2007 5:54 PM

kenbalbari wrote:

But perhaps we should start another thread if we want to get into this technical debate?
I agree. Let's let this debate in this thread die.

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