Opinions on Extenders, please?

[PajamaGuy]

Extender EF 2x III - or the EF 1.4x III.  Same price.  Other than the obvious, why one over the other?  Are the optics equal?

Thanks!

[RobertTheFat]

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@TTMartin wrote:

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@RobertTheFat wrote:

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@TTMartin wrote:

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@ebiggs1 wrote:

"...  and can't wait for grandson's basketball.. ..."  "... no I wouldn't use it there, ..."

Why?  It will be the best choice you can make if you also take a shorter zoom too.  Like the 24-70mm f2.8 for instance.  You know the action is not always on your end?  Sometimes it is.

For baseball it will be your shorter zoom.  You might add the 100-400 II to that bag.

Personally for me I will amost always (99% of the time) choose post editing over an extender.  Yes, I reserve a few situations where I would use an extender but not many.

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Basketball indoors is often done in very poor lighting conditions. Losing a stop or two of light using a TC in those conditions usually isn't practical, especially when using a crop sensor camera like the 7D Mk II that already captures one stop less total light tnan a full frame camera. 

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A crop sensor camera may or may not capture less total light than a full-frame camera, but that's beside the point. The crop sensor camera needs, and therefore uses, less total light because it has less sensor area to cover. It's not at any competitive disadvantage in light gathering power, as compared to a FF camera.

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I don't know why so many people have such a hard time with the concept. A given exposure lets in a set amount of light PER UNIT AREA. A full frame sensor has more units of area, so receives more total light for any given exposure. 

But the same amount per unit area, which is what matters.

image from quora.com

So for crop sensor cameras, at any given ISO the signal is amplified one stop more than it would be on a full frame camera.. This is why full frame cameras seem to have about a one stop advantage in terms of ISO noise.

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As I understand it, the reason FF cameras tend to be less noisy is that they usually have a larger pixel size. Very high-resolution FF cameras lack that advantage.

I don't claim to be an expert on the subject, so maybe I am having "a hard time with the concept". But for now I stand behind what I said in my previous post.

[TTMartin]

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@RobertTheFat wrote:

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@TTMartin wrote:

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@RobertTheFat wrote:

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@TTMartin wrote:

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@ebiggs1 wrote:

"...  and can't wait for grandson's basketball.. ..."  "... no I wouldn't use it there, ..."

Why?  It will be the best choice you can make if you also take a shorter zoom too.  Like the 24-70mm f2.8 for instance.  You know the action is not always on your end?  Sometimes it is.

For baseball it will be your shorter zoom.  You might add the 100-400 II to that bag.

Personally for me I will amost always (99% of the time) choose post editing over an extender.  Yes, I reserve a few situations where I would use an extender but not many.

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Basketball indoors is often done in very poor lighting conditions. Losing a stop or two of light using a TC in those conditions usually isn't practical, especially when using a crop sensor camera like the 7D Mk II that already captures one stop less total light tnan a full frame camera. 

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A crop sensor camera may or may not capture less total light than a full-frame camera, but that's beside the point. The crop sensor camera needs, and therefore uses, less total light because it has less sensor area to cover. It's not at any competitive disadvantage in light gathering power, as compared to a FF camera.

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I don't know why so many people have such a hard time with the concept. A given exposure lets in a set amount of light PER UNIT AREA. A full frame sensor has more units of area, so receives more total light for any given exposure. 

But the same amount per unit area, which is what matters.

image from quora.com

So for crop sensor cameras, at any given ISO the signal is amplified one stop more than it would be on a full frame camera.. This is why full frame cameras seem to have about a one stop advantage in terms of ISO noise.

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As I understand it, the reason FF cameras tend to be less noisy is that they usually have a larger pixel size. Very high-resolution FF cameras lack that advantage.

I don't claim to be an expert on the subject, so maybe I am having "a hard time with the concept". But for now I stand behind what I said in my previous post.

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The 5DS has about the same pixel size as a crop sensor camera. It still has about a one stop advantage in noise at higher ISOs (full photo), because it has a larger sensor and gathers more total light for any given exposure.

[ebiggs1]

"I don't know why so many people have such a hard time with the concept."

The reason is, the "concept" is wrong.

Think of two plastic cups of Coke. If I buy a 44 oz Coke form Quiktrip but I only put 32 oz in it, the cup is about 3/4th full. If I then pour the Coke from the 44 oz into a 32 oz cup, it will be full. Did your Coke get bigger? Did it change in any way? No, you are just using a different reference point as to what full means.

Now for aperture, it is a mathematical formula. If I have a 500mm lens with a 125mm front objective element, the f/stop will be f/4. That is what it is. It can not change. Changing the size of the sensor doesn't change that formula. If you assume the same pixel pitch for both the cropper and the full frame, they will receive the same amount of light, regardless of the size of the sensor.

A properly exposed shot at f/8 and 1/500th of a second at ISO 100 will remain properly exposed regardless of whether the sensor is the tiny chip in your iPhone 6s or a medium format or a cropper or a FF sensor. Same, same, same.

[TTMartin]

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@ebiggs1 wrote:

"I don't know why so many people have such a hard time with the concept."

The reason is, the "concept" is wrong.

Think of two plastic cups of Coke. If I buy a 44 oz Coke form Quiktrip but I only put 32 oz in it, the cup is about 3/4th full. If I then pour the Coke from the 44 oz into a 32 oz cup, it will be full. Did your Coke get bigger? Did it change in any way? No, you are just using a different reference point as to what full means.

Now for aperture, it is a mathematical formula. If I have a 500mm lens with a 125mm front objective element, the f/stop will be f/4. That is what it is. It can not change. Changing the size of the sensor doesn't change that formula. If you assume the same pixel pitch for both the cropper and the full frame, they will receive the same amount of light, regardless of the size of the sensor.

A properly exposed shot at f/8 and 1/500th of a second at ISO 100 will remain properly exposed regardless of whether the sensor is the tiny chip in your iPhone 6s or a medium format or a cropper or a FF sensor. Same, same, same.

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The concept is NOT wrong and you are very confused.

No the size of the sensor doesn't change the formula, but, it does change the total amount of light that falls on it. So while the size of the cups is totally irrelevant. The total surface are covered by the cups is relevant. If you cover half a tennis court with solo cups, or you cover the whole tennis court with solo cups, it will effect the total amount of water collected when it rains. That's because just like the light coming through the lens, the rain that falls where you don't have cups is not collected. The same is true of sensors, when the light comes through the lens, if you have a smaller sensor, more light falls outside of the sensor than if you have a different sensor.

The reason why an iPhone 6, crop sensor camera, and full frame camera all use the same settings, is because the manufacturers of those devices vary the amount of signal amplification so that they all can use the same settings. The smaller sensors get more signal amplification, because the gathered less total light.

[ebiggs1]

"The concept is NOT wrong and you are very confused."

Well Mr./Ms. Martin, you are right about one part. I am usually “very confused”. I have gotten used it it over the years. However on this concept I am not.

No sensor uses all the light a lens provides. Some is always out of the image circle that any lens makes since no lens makes a square image. Where you go wrong in your theory and the others that think like you is there are many conditions that make a photograph. Sensor size is simply one. Signal to noise, dynamic range, signal amplification along with pixel size and pixel placement. How close, tightly packed, to one another pixels are and so on, etc.

When we construct a lens it is fixed. It can not change its parameters, ever. It does not care what sensor you choose to put behind it.

If said lens is set to f4, every pixel in that sensor is going to get f4. No matter what size the sensor is, they all get f4. If this were not true, hand held light meters would not work. Because there would have to be a different one for every sensor made.

You can prove it to yourself. Put a lens on your cropper and take a photo. A nice daylight outdoor scene. Put the same lens on your FF take the same photo. The settings will be the same if you did both exactly the same way.

Another point where you and the others go wrong is forgetting the AOV. If your photo, from above, eliminated much of a brighter area you may get a different reading and as such you will mistakenly assume the smaller sensor got less light. It didn't. AOV is just another factor in this myriad of exposure settings in a complicated world of photography.

And this brings us to the topic of DOF. You are correct in assuming DOF increases by about one stop. When identical lenses are compared on a crop vs FF. This changes the AOV so a resulting increase in f-ratio. This changes the scene or subject also. It does NOT change the lens or the sensor. They remain exactly the same. f4 remains f4. Each pixel is still getting f4 no matter how much light is wasted out side the sensor's physical dimensions.

All you need to remember is, no difference in f-stop because the exposure rules are the same. You do know the “triangle of exposure”? It matters not what the sensor size is. Does it?

If both cameras have the same shutter speed and ISO settings, the aperture will be the same as well. It does not matter what size the sensor is.

My advice. Instead of setting behind your keyboard, explaining how confused I am, go outside and use your camera. Play with it. Learn it. Learn all its idiosyncrasies. Get it off the green square and P. It's fun. It's great.

[TCampbell]

Ernie is right.  It does surprise me that this topic has created so much confusion.  Only the "unit area" matters, not the "total area".

Perhaps a different analogy...

Suppose we place a movie projector at one end of a room.  At the other end of the room we place a portable projection screen that measures 8' wide by 6' tall (4:3 screen).  We adjust the projector so that the image fits on this screen perfectly.

Now suppose that we remove the 8x6' screen and replace it with a smaller 6x4.5' screen located precisely where the 8x6' screen used to be.  We (and this is the important bit) DO NOT TOUCH the projector or adjust it in any way.

Would we expect the image on that screen to suddenly get brigheter simply because the second screen is smaller?

The light doesn't "know" the screen is smaller and somehow manage to conserve itself from being wasted ... The light that misses the screen and lands on the wall behind is simply wasted light.

The same is true of a crop frame camera.  The exposure settings are based entirely on the lens and not on the sensor.  The sensor has no bearing in the exposure formula.  If you swap out a full frame sensor for a crop-frame sensor then the lens will still continue to pass in the same amount of light... It's just that more of that light will now be wasted and the amount of light absorbed by any given photo-site on the surface of the sensor (assuming like-sized photo-sites) will be the same.

If using the tennis court and solo-cups analogy... It doesn't matter how many solo cups are on the tennis court.   If 1" of rainfall lands on the tennis court, then every solo cup will have 1" of rain in it.  The cups won't get 2" of rain collected if we deploy only half as many cups.

We only care to measure the light collected "per unit area".  A grain of silver-halide on a film negative doesn't know how many other grains of silver-halide are on that same film negative.

Another way to think of it is that both "cameras" collect exactly the same amount of light.  It's just that the camera with a smaller sensor wastes more of that light.

In defense of Mr. Martin... there is a situation in which the screen size does matter.  Suppose we are using a darkroom enlarger and producing a print.  We adjust the projector to produce a small 4x5 and we determine that we decide that 4 seconds of light from the projector makes the ideal exposure for the print.  But now we want to make an 8x10 print.   So we move the enlarger head up the track so that it will project a larger image.   The projector bulb pumps out the same amount of light regardless of the paper size.  So the fact that we are printing on a surface which is 4x larger total area means that each "unit area" of paper will now only get 1/4th as much light (we are spreading the photons thinner.  Think of spreading the same amount of peanut butter on a piece of bread which is 4x larger.  The peanut butter has to be spread thinner.). This means we will have to increase the exposure duration by 4x to compensate.  But this is only true of the darkroom enlarger because we physically changed the distance between the head and the table surface.  In a DSLR, we do not change the distance from the lens and the sensor -- so the darkroom enlarger example (changing paper size) doesn't apply.

[ebiggs1]

Tim as usual you are the one with words.     You make it more clear than I apparently was able or even can.

"In defense of Mr. Martin... there is a situation in which the screen size does matter.  Suppose we are using a darkroom enlarger and producing a print.  We adjust the projector to produce a small 4x5 and we determine that we decide that 4 seconds of light from the projector makes the ideal exposure for the print.  But now we want to make an 8x10 print.   So we move the enlarger head up the track so that it will project a larger image.   The projector bulb pumps out the same amount of light regardless of the paper size.  So the fact that we are printing on a surface which is 4x larger total area means that each "unit area" of paper will now only get 1/4th as much light (we are spreading the photons thinner.  ... But this is only true of the darkroom enlarger because we physically changed the distance between the head and the table surface.  In a DSLR, we do not change the distance from the lens and the sensor -- so the darkroom enlarger example (changing paper size) doesn't apply."

And again in defense of Mr. Martin, this example is germane to DOF.  DOF in a crop (1.6x) does indeed does have a 1 stop (approx.) increase.  Moving the enlarger head changed the AOV.  This is where he and the others that believe in this theory go astray.

I believe it is a lack of working knowledge with the equipment.  There is only so much one can learn from books or the internet.  At some point you must get out, hands on, and do.

[TTMartin]

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@TCampbell wrote:

Ernie is right.  It does surprise me that this topic has created so much confusion.  Only the "unit area" matters, not the "total area".

Perhaps a different analogy...

Suppose we place a movie projector at one end of a room.  At the other end of the room we place a portable projection screen that measures 8' wide by 6' tall (4:3 screen).  We adjust the projector so that the image fits on this screen perfectly.

Now suppose that we remove the 8x6' screen and replace it with a smaller 6x4.5' screen located precisely where the 8x6' screen used to be.  We (and this is the important bit) DO NOT TOUCH the projector or adjust it in any way.

Would we expect the image on that screen to suddenly get brigheter simply because the second screen is smaller?

The light doesn't "know" the screen is smaller and somehow manage to conserve itself from being wasted ... The light that misses the screen and lands on the wall behind is simply wasted light.

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Exactly and this is exactly what happens with a full frame camera vs a crop sensor camera. When you have crop sensor camera the light that falls outside of it is wasted. 

This is why a full frame camera that has more surface area collects more TOTAL light. Because less light from any given exposure is wasted falling outside of the sensor. 

So the same amount of light per square mm comes through the lens, a full frame sensor has more square mm and collects more TOTAL light, than a crop sensor camera with less square mm of area to collect the light.

Camera manufactures compensate for this difference in TOTAL light collected by changing the signal amplification so as photographers we don't have to worry about it or see it (except in noise).

A good example of this concept is the Metabones Speed Booster, it takes all of the light coming through a the full frame lens and focuses it on the crop sensor. Since the crop sensor is now receives the same total light that a full frame sensor would you now gain one stop. (I'm PMing you their White Paper)

It is also the reason you lose a stop or two of light when using a teleconverter. The teleconverter isn't semi opaque and doesn't absorbs or block a stop of light, it simply spreads it out so more of the light coming through the lens falls outside of the sensor and the sensor receives less of the total light that is coming through the lens.

[ebiggs1]

 In this excellent example shows the f-stop for each pixel id not and will not change.

"Suppose we place a movie projector at one end of a room.  At the other end of the room we place a portable projection screen that measures 8' wide by 6' tall (4:3 screen).  We adjust the projector so that the image fits on this screen perfectly.

Now suppose that we remove the 8x6' screen and replace it with a smaller 6x4.5' screen located precisely where the 8x6' screen used to be.  We (and this is the important bit) DO NOT TOUCH the projector or adjust it in any way.

Would we expect the image on that screen to suddenly get brigheter simply because the second screen is smaller?

The light doesn't "know" the screen is smaller and somehow manage to conserve itself from being wasted ... The light that misses the screen and lands on the wall behind is simply wasted light."

Where we depart in agrement, as I believe we are both saying, nearly, the same thing only differently, is the AOV.  I think?   I agree when the AOV or DOF is changed you can, perhaps, loose a stop (1.6 cropper approx.).  You do not change the lens in any way.  In Tim's other example where he moved the enlarger head, the AOV was changed.  Right? 

Instead of thinking of it as the total light that hits the sensor, think of it as the intensity of light that hits the sensor. That remains unchanged regardless of the crop factor, assuming an evenly lighted subject. This is what the exposure meter uses to determine the correct exposure.  You don't need a projector to see this.  Put a white piece of paper in the center of a round table.  Look at it.  Fold it in half.  Did it get brighter?  Darker?  No it stayed the same.

There is also a problem when trying to compare sensors.  It is nearly impossible to keep everything exact. And, about your noise claims, no matter what the pixel size, larger sensors do have more light-gathering area.  A larger sensor with smaller pixels can still have lower apparent noise than even a smaller sensor with larger pixels. This is because noise in the FF camera gets enlarged less.  Again a fault of AOVor DOF. This is the signal-to-noise ratio.  A consideration in photography is "shoot to the right".  Which means to over expose slightly to help reduce noise instead of unexposed.  If noise is your big concern, that is.

This question never came up back in the day when we used medium format and 35mm film cameras, because everybody just knew that f/4 is f/4, no matter what.  Think of it the other way.  Do you gain f-stops if you shoot a Phase One?

I don't see any further fruits coming from this.  We are apparently not going to change each others minds.  The tern "crop camera" is a mess in the first place.  

I have made a life-long career out of what I have seen and learned.  It has worked well for me. Now you are free to decide what works for you.

[TTMartin]

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@ebiggs1 wrote:

Instead of thinking of it as the total light that hits the sensor, think of it as the intensity of light that hits the sensor. That remains unchanged regardless of the crop factor, assuming an evenly lighted subject. This is what the exposure meter uses to determine the correct exposure.  You don't need a projector to see this.  Put a white piece of paper in the center of a round table.  Look at it.  Fold it in half.  Did it get brighter?  Darker?  No it stayed the same. 

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If you have even constant light and you place your piece of paper on a table it will get hit by a certain number of photons per minute. When you fold the paper in half, now half of those photons now hit the table which is no longer covered by the paper and half hit the folded paper. The full piece of paper receives twice the total number of photons per minute or light than the folded paper does. The same is true of a crop sensor and a full frame sensor.

So what does this mean to us as photographers. If we have a full frame camera with an EF 85mm f/1.8 lens set at f/1.8, ISO 100, 1/100 and a crop camera with a 50mm f/1.8 lens set at f/1.8, ISO 100, 1/100 both will have approximately the same angle of view and the same exposure, but, since the full frame camera sensor is larger it has gathered more TOTAL light. As you increase ISO this difference in total light gathered becomes apparent in noise. This is why full frame cameras have approximately a one stop noise advantage at high ISOs. This is because Canon and every other camera manufacturer compensates for the differences in total light received by sensors, by changing the amplification of signal. So as photographers we don't have to worry about it, except that it is the reason that smaller sensors seem noisier than larger sensors. The smaller the sensor the more amplification that is needed to simulate the same ISO..

Now lets look that crop camera with the 50mm f/1.8 lens set at f/1.8, ISO 100, 1/100 and the full frame camera with the 50mm  f/1.8 lens and a 1.4X TC wide open, ISO 100, 1/100. Now you again have approximately the same angle of view, but, the image area that fell on the crop sensor is now spread out over the entire full frame sensor. The photons that would have hit the crop sensor are now spread over the full frame sensor. Both sensors are now receiving the same TOTAL light, but, since the full frame camera isn't automatically compensating for the fact that it is receiving less light, due to the TC, you will be one stop underexposed.