[ Tech ] - F-stop versus T-stop : Is your f1.4 lens as bright as you thought it is?


Oh, sorry. I din reply about the photo because it was not relevant to the discussion about light loss or light not captured well at the sensor.

To answer the question, the photo is metered perfectly by the iESP. The club was as dark as the photo shows. It is a "what u see is what u get" result. As perfect as it can be. I dun think I even adjusted the exposure on the PC. My point of showing the photo is that the humble EPL1 can take photos like this in a virtually dark situation in a club. So I dun understand why people are so fixated on low light and have to get large sensor camera to capture the limited light available and use large aperture fast lenses.

As for whether the photo can tell me anything about light loss....not directly. This is because this photo's exposure is based on the exposure settings set by the camera on-board algorithms. So it will not directly tell u anything about light not well captured by the sensor or light loss. Perhaps, if u extrapolated it, you MAY be able to work out how much light loss there is. But the caveat is that the ISO numbers must be comparable. What the article is suggesting is that some manufacturers ISO 100 is not really 100, but maybe 200 for example. So how well exposed the photo is is not an indication of how much light is lost. Photo exposure is based on camera exposure settings.

Telecentricity is about how well the sensor captures the light. If a system is more telecentric, it just means that more light will be better captured. It also means that colours - different light wavelengths - will also be better captured by the digital sensor. It may also imply that light waves are also captured more accurately because the sensor will be less affected by indirect light waves. The converse of this means that the sensor only picks up direct light waves, which is what you want. What all these means is that the image will have better colours and better image rendition, and sharper too. For people who like how the Olympus photos and colours look, this may be one of the reasons for it, in addition, to the lens, and the JPEG engine.

Just think about it? When Olympus abandoned OM when they moved into digital, they had a clean slate to work with. Size of the digital sensor could have been anything. It could have been 135 FF size, or bigger, or smaller. But yet, from that clean slate, they choose the 4/3 format which turned out to be a smaller sensor than the 135 mm size. These are a bunch of scientists and engineers who worked out all these based on their knowledge of physics. And they are not just engineers, because they really understand also, what photography is. And neither are they marketing people, because if u had allowed the marketing brain to take over, they would have produced a sensor that is way bigger...as I said, it is easier to market something that is bigger or larger. And Olympus, to me, is a company focused on the art of photography, by actually working out the science behind it, so that we as consumers, have the tools which allow us to take more photos.

To put it more succinctly, Olympus allows me to spend more time taking photographs, spend more time with the camera. If u want to take photos, but spend more time behind the PC, u can shoot other brands. What do I mean by this, well, for example, SSWF. No SSWF, u may have to spend more time in PP to remove dust spots from your photos. Less than optimal JPEG engine, u need to shoot RAW and then process yourself for better colours. Addition of RAW in workflow, takes up significant time and resources. For me, I realized that I have virtually no workflow to speak off. The only things that I do, IF I DO IT, is perhaps some cropping and exposure adjustment. Cropping is because of my poor composition or lack of attention to background, and exposure adjustment because of operator using wrong exposure settings. A lot of people do not realize this 100% FOV that Olympus gives us. This means that if I compose properly, the images do not need to be cropped routinely. If u have a camera that has a 98% FOV, u will find subject isolation is difficult to achieve without performing routine cropping. I could go on but I hope the point is made.

All the innovations that Olympus have developed, is obviously very scientific and very technical. But they all work in the background. As consumers, we do not need to really understand the physics. Just pick up the camear and start shooting. But if u understand some basic concept of why your tool is like this, its strengths etc, u can leverage and perhaps take better photos.
 

What the article is suggesting is that some manufacturers ISO 100 is not really 100, but maybe 200 for example. So how well exposed the photo is is not an indication of how much light is lost. Photo exposure is based on camera exposure settings.

Olympus does it too, at f/8 even, shot with 12-60 :
http://www.lemis.com/grog/photography/DxO-sensor-test.php

But in the real world beyond DXO, which measures ISO differently from manufacturers (of course its results will be different), no problem for me. I've never encountered such automatic change in exposure, whether outdoors or even in the studio where exposure is more controlled. It's all about clipping, apparently in the measurements, and I don't take such shots on digital which I know doesn't have the latitude of film.

The test results in the link above is eye-opening though, as it's a super simple daylight shot ! Never have I encountered that in any digital camera I used.

As for fast lens, no problems too in the real world, what I saw and exposed is what I got. Tested against a 1-degree spot meter even, no issues, and film and digital shooting the same scene had more or less the same exposure results. And of course fast lens is not all about light gathering, and they work as expected.

Exposure is also subjective, at least for more artistic photographers. Especially with live view/evf, where one can decide on the spot which exposure one wants just by looking at what is shown on screen/evf. Photographers can work with exposure to set a certain mood for example. Other photographers may expose it differently, and experienced and confident shooters wouldn't care about what others say, it's their picture after all.

Anyway, since I've had no problems in many years, it's not an issue for me. YMMV.

As for sensor sizes, I treat them all as different animals, each have their own merit.
 

Just a thought, if you shot using an adapted/ non-electronically coupled lens would the system still subliminally bump it ISO?
 


Utter silliness. Digital cameras are inherently systems consisting of lenses, sensors and software (including firmware). This is not film where you take a sensor and slap it into different camera bodies and formats. Simplifying, ISO/EI is just a measure of apparent "brightness" of a final image, and getting to that image requires a whole process including software manipulations before a file is written to your flash memory card. Who cares how many millivolts or milliamps are coming off the sensor ? Yeah, yeah, more gain means more noise, but different films with the same ISO ratings had different grain characteristics too, and many people liked it that way.
 

alot of ppl talking about needing to stop down f/1.2 lenses to get usable, sharp results... of the 4 different f/1.2 lenses ive used (canon FL, FD SSC, Nikkor 55, 50 ais) they were all usably sharp at f/1.2 even the 1960s canon FL lens.

my nikkor 50 f/1.2 AIS IMHO is better than the 50 f/1.4 for sharpness, colour rendition, contrast and especially skin tone rendition. the only biggest reason i stop down is if i want more depth of field and not more sharpness.

but its not all about sharpness...

lenses are tailored to different needs. generally, there is a fast and slow f stop for any aperture. i ll take the f/1.8, 1.4 and 1.2 50mm lenses for example. 1.8 is cheap and good, emphasis on sharpness, contrast and compactness. the 1.4 is faster for more low light work, brighter vf, subject isolation, BUT it is still meant as an all purpose lens.

the 1.2(fastest) lenses are not designed just for sharpness.. usually optimized for portraiture with different rendition, better colours, better bokeh. can be seen in how the 50 1.2, 85 1.4, 105 f2, 135 f2 are all not the sharpest lenses (but not soft either). they do however, have the most pleasing bokeh and very very good subject isolation.

note that while t stop is important, the f stop is the one that dictates DOF. so if u want less dof, it really doesnt matter. minolta even has a 135 f/2.8 with a t stop of 4.5. its purposely done to get better bokeh..

photography isnt all about sharpness and resolution.. if u see past that, lenses can be good/better for other things.. so, in summary, choose the lens that give you the output that YOU want. for me, i like my fast lenses and anything slower than f2 is usually abit less 'special'


Just a thought, if you shot using an adapted/ non-electronically coupled lens would the system still subliminally bump it ISO?

no it wont. that why with the AF chip, or inputting the correct FL and F stop(for nikon) will affect the exposure. when i dun input f stop, my 50 1.2 images become underexposed by about 1/2-1/3 stop. my observations agree with the paper. without changing any settings, when i input the f stop info, the resulting picture is brighter.
 

Last edited:
Just think about it? When Olympus abandoned OM when they moved into digital, they had a clean slate to work with. Size of the digital sensor could have been anything. It could have been 135 FF size, or bigger, or smaller. But yet, from that clean slate, they choose the 4/3 format which turned out to be a smaller sensor than the 135 mm size. These are a bunch of scientists and engineers who worked out all these based on their knowledge of physics. And they are not just engineers, because they really understand also, what photography is. And neither are they marketing people, because if u had allowed the marketing brain to take over, they would have produced a sensor that is way bigger...as I said, it is easier to market something that is bigger or larger. And Olympus, to me, is a company focused on the art of photography, by actually working out the science behind it, so that we as consumers, have the tools which allow us to take more photos.

/QUOTE]

If what you said is correct, then, all the engineers of Canon, Nikon, Pentax, Sony, Tamron, Sigma, Leica, Zeiss and all others from the MF manufacturers are "fools"?
 

If what you said is correct, then, all the engineers of Canon, Nikon, Pentax, Sony, Tamron, Sigma, Leica, Zeiss and all others from the MF manufacturers are "fools"?

Maybe not but Olympus treats optics as the business and photography as a hobby.

Some groups, like the third party lens designers/makers, must find profitable business in adaptations. The most entrenched mounts get their attention, not necessarily the best. Considering the quality of Sigma products, I'm surprised that they're still in business. They produce a handful of lenses of high quality.

I'm not sure whether Olympus was brave or foolish or some combination to switch formats, but they saw the clean slate as a great opportunity to do digital photography correctly. It's something a company would rarely do, but they've had several bold steps along their timeline.
 

@Anthony Lee : What I say is correct, but that does not mean that everyone else is a fool because of YOUR assumption. Photography is a complex business and there are many factors that affect the image output. Also, at the end of the day, the bottom line is economics. Even if u have a great idea and it MAY be the right idea, but if you cannot convince the masses that your idea is right, u will still fail as a business. This thread alone has proved it. It is not easy to convince people of the benefits of the 4/3 format. Even people who have bought into it, some do not even care about it or even understand it. To be honest, its difficult to sell this kind of concept. Try telling people that a smaller sensor is better....."telecentric" u say!....du...uh? "scratch scratch"...

On the other hand, if u can market something that the masses can understand AND believe easily, u can sell it. A very good example is the 135 "Full Frame" format. Big is better....a bigger sensor can capture more light, bigger sensor, means bigger pixels to catch the light. U dun even need to show formula or show data. This concept is so simple, that people will believe it without even having to be convinced. That is why there is this obsession with "full frame".

To me, Olympus is a bold and courageous company. When they realized that digital is the future of photography, they abandones the OM standard although they had great successes there. I think not many company would do something like that. Of course, they lost everyone. I think it would be the same if they were to abandon the 4/3 format. As a camera company, they were able to realize the limitations of the digital sensor versus a 135 mm film. Because of that, they probably just asked a simple question .... "What standard should now be adopted now that digital is the future for SLR photography?"

The result is based on the work of a engineer who did a PhD on digital sensor technology and the 4/3 format was produced. To me, I would not be surprise if in the future, the 4/3 format may become replaced with the m4/3 format. Even though I just invested in the E5, it does not bother me. As far as I am concerned, Olympus has been making cameras that allow me to spend all my time in photography behind the camera and virtually no time at the PC doing post processing. In the future, I believe that mirrorless will be the way to go for DSLR....once they can sort out the response time.
 

Last edited:
@Anthony Lee : What I say is correct, but that does not mean that everyone else is a fool because of YOUR assumption. Photography is a complex business and there are many factors that affect the image output. Also, at the end of the day, the bottom line is economics. Even if u have a great idea and it MAY be the right idea, but if you cannot convince the masses that your idea is right, u will still fail as a business. This thread alone has proved it. It is not easy to convince people of the benefits of the 4/3 format. Even people who have bought into it, some do not even care about it or even understand it. To be honest, its difficult to sell this kind of concept. Try telling people that a smaller sensor is better....."telecentric" u say!....du...uh? "scratch scratch"...

On the other hand, if u can market something that the masses can understand AND believe easily, u can sell it. A very good example is the 135 "Full Frame" format. Big is better....a bigger sensor can capture more light, bigger sensor, means bigger pixels to catch the light. U dun even need to show formula or show data. This concept is so simple, that people will believe it without even having to be convinced. That is why there is this obsession with "full frame".

To me, Olympus is a bold and courageous company. When they realized that digital is the future of photography, they abandones the OM standard although they had great successes there. I think not many company would do something like that. Of course, they lost everyone. I think it would be the same if they were to abandon the 4/3 format. As a camera company, they were able to realize the limitations of the digital sensor versus a 135 mm film. Because of that, they probably just asked a simple question .... "What standard should now be adopted now that digital is the future for SLR photography?"

The result is based on the work of a engineer who did a PhD on digital sensor technology and the 4/3 format was produced. To me, I would not be surprise if in the future, the 4/3 format may become replaced with the m4/3 format. Even though I just invested in the E5, it does not bother me. As far as I am concerned, Olympus has been making cameras that allow me to spend all my time in photography behind the camera and virtually no time at the PC doing post processing. In the future, I believe that mirrorless will be the way to go for DSLR....once they can sort out the response time.

Businesses are in the business of making money. Profitability, growth, market share and end user acceptance are the only consideration. If you are on top, then you are the best. If you are at the bottom, regardless of your believe, you can hardly survive. Further, this business is about electronics and softwares. It's not about sensor size or format. If you have all the technologies in-house, then you are at an advantage. If you do not, you are at the mercy of others, and your survival will depend on how fast you adapt and move. If Olympus still have engineers who are hobby riders, then that's the main reason why they are where they are. Personally, I prefer Olympus to get out of this hole which they dug for themselves fast, otherwise, when other big guns get involve in alternative EVILs, like Sony and Samsung, that may spell the end of Olympus.
 

Businesses are in the business of making money. Profitability, growth, market share and end user acceptance are the only consideration. If you are on top, then you are the best. If you are at the bottom, regardless of your believe, you can hardly survive. Further, this business is about electronics and softwares. It's not about sensor size or format. If you have all the technologies in-house, then you are at an advantage. If you do not, you are at the mercy of others, and your survival will depend on how fast you adapt and move. If Olympus still have engineers who are hobby riders, then that's the main reason why they are where they are. Personally, I prefer Olympus to get out of this hole which they dug for themselves fast, otherwise, when other big guns get involve in alternative EVILs, like Sony and Samsung, that may spell the end of Olympus.

No disagreement here that bottomline is the be all and end all.

Anyway, Olympus has always been the technological innovation leader in terms of their camera. They have always been the one to think out of the box and innovate. Unfortunately, although they have successes, for some reason, they cannot seem to maintain on capitalize on it. They need to be more like apple, but they are not. Also, they dun get any mass market credit for their innovations which are usually very practical and functional. I blame that on their marketing.

Whatever the case, although they are not the market leader, there are still people who appreciate Olympus as a camera maker and will buy their products. Whether Olympus survives or not eventually, its all up to them. But for now, they are still riding on the success of their PENS. The greatest compliment is imitation. You cannot deny that Olympus proved that EVILS are the next big thing. The fact that all the big guns are jumping in, is testament to that. But unfortunately, it may be that once Canikon comes in, they may take EVILS away. And the reason again, is marketing. Olympus needs to market better. They need to market their innovations better.

Look at the Canon 60D. They way that Canon is marketing it, it makes it look like Canon is the one that has come up with the variable angle LCD. Sheesh.....They call it revolutionary. Hello....I think that revolution is nearly 3 years behind time now..LOL!
 

No disagreement here that bottomline is the be all and end all.

Anyway, Olympus has always been the technological innovation leader in terms of their camera. They have always been the one to think out of the box and innovate. Unfortunately, although they have successes, for some reason, they cannot seem to maintain on capitalize on it. They need to be more like apple, but they are not. Also, they dun get any mass market credit for their innovations which are usually very practical and functional. I blame that on their marketing.

Whatever the case, although they are not the market leader, there are still people who appreciate Olympus as a camera maker and will buy their products. Whether Olympus survives or not eventually, its all up to them. But for now, they are still riding on the success of their PENS. The greatest compliment is imitation. You cannot deny that Olympus proved that EVILS are the next big thing. The fact that all the big guns are jumping in, is testament to that. But unfortunately, it may be that once Canikon comes in, they may take EVILS away. And the reason again, is marketing. Olympus needs to market better. They need to market their innovations better.

Look at the Canon 60D. They way that Canon is marketing it, it makes it look like Canon is the one that has come up with the variable angle LCD. Sheesh.....They call it revolutionary. Hello....I think that revolution is nearly 3 years behind time now..LOL!

I am very neutral and for consumers, we need close competition amongst the manufacturers to get better worth for our money. Since you mentioned the 60D, it's rated very lowly at DXO compared to the close competitors especially the E5, K5 and D7000. But Canon wins the game because the 60D was out 2-3months ahead of the pack and by the time the D7000 is available worldwide, imagine how many units of the 60D being sold. Personally, I would say that the 60D is the best value DSLR for entry level users. To me it's a complete success regardless of what you and I think of it. That's the name of the game.
 

Back
Top