R5 lunar photography with stacked EF extenders

Leeuw wrote:

Bigger wrote:

Leeuw wrote:

Canon’s 2x ii extender can be stacked with the type iii extenders. Having 2x ii, 2x iii and 1,4x iii gives me several options to combine with my EF 600 f/4 II and R5.
This thread inspires me to start some experiments. For instance how would the 2x + 2x double stack perform. Maybe a bridge too far but why not give it a try.

What I have found from my terrestrial testing is that the EF 600 f/4 II definitely benefits from a 2x converter, even on a 5DsR with 4um pixels. The added 1.4x seems to help a little, especially on an R5, but I don't think there is any resolution left to get beyond that with ~4um pixels. The 2x + 2x might help with an R6 or other ~6um pixel camera, though.

Thanks, I will definitely try the 2x + 1.4x stack and see if the 2x + 2x does add something but probably not. Maybe a 8K video image stack can extract some extra details…..

The image stacking doesn't do much to increase B&W detail--it mostly helps with color detail by filling in the missing color sub-pixel info. That's not much help for lunar photography since the subject is B&W (but it will help keep it that way by reducing false color).

Extra focal length is good when the lens (or telescope) has more resolution than the sensor. But once the lens becomes the limiting factor, additional FL doesn't help resolve more detail, it just magnifies and multiplies the aberrations.

Bigger wrote:

Yes, with the control ring. All 8 pins seem to have independent springs, and the force seems comparable to Canon lenses (but I didn't attempt to measure this). The adjacent pins didn't move.

OK - then it better than mine. As it seems also easier to mod (less material to remove), I'll have to get one of those. Disassembly is likely not an option, though.

I also have the Commlite CM-EF-EOS R, but I can't find it at the moment. If I locate it, I'll check it and report back later.

That would be nice - thanks!

J.K.T. wrote:

Bigger wrote:

Yes, with the control ring. All 8 pins seem to have independent springs, and the force seems comparable to Canon lenses (but I didn't attempt to measure this). The adjacent pins didn't move.

OK - then it better than mine. As it seems also easier to mod (less material to remove), I'll have to get one of those. Disassembly is likely not an option, though.

Yes, you just need to remove the high ridge at the casting seam on the plastic baffle, and just around the contact pin bump. You can almost force the RF 1.4x rubber "nose" inside the adapter, but don't do it because it may be more difficult to separate them later. I just used an ordinary half-round file and a light touch--just enough to get the nose to fit inside. Then cleaned well with alcohol to remove any filings.

Leeuw wrote:

Bigger wrote:

The image stacking doesn't do much to increase B&W detail--it mostly helps with color detail by filling in the missing color sub-pixel info. That's not much help for lunar photography since the subject is B&W (but it will help keep it that way by reducing false color).

Don’t rule out seeing effects (air turbulences) with these magnifications and subjects at infinity. Smart stacking uses the best frames and even best parts of each frame providing more detail and less noise. For planetary and solar imaging I have used the 600mm with 1.4x extender plus 5x Barlow with great details but only after stacking many frames. A single frame hardly shows any detail.

Seeing is an issue, and smart stacking can address that issue, but it can't give the base lens more resolution than it has.

Extra focal length is good when the lens (or telescope) has more resolution than the sensor. But once the lens becomes the limiting factor, additional FL doesn't help resolve more detail, it just magnifies and multiplies the aberrations.

Sure. But the EF 600mm has proven to me to have a surplus of resolution and can be extended a whole lot I'll give the 2x double stack combined with avi stack a try without expectations.

Yes, the EF 600mm II can still alias the center of a siemens star with a 2x iii; but not with a 2x iii + 1.4x iii on a 4um pixel camera, so I think that's past the point of diminishing returns. But by all means try it and see.

Tristimulus wrote:

Why many photographers fail to get the most out of 2x teleconverters is usually down to atmospheric turbulence (air currents) and sloppy technique.

Or they compare bare lens images to 2x TC images at the same magnification, not the same scale.

J.K.T. wrote:

Bigger wrote:

Yes, with the control ring. All 8 pins seem to have independent springs, and the force seems comparable to Canon lenses (but I didn't attempt to measure this). The adjacent pins didn't move.

OK - then it better than mine. As it seems also easier to mod (less material to remove), I'll have to get one of those. Disassembly is likely not an option, though.

I also have the Commlite CM-EF-EOS R, but I can't find it at the moment. If I locate it, I'll check it and report back later.

That would be nice - thanks!

I found the Commlite CM-EF-EOS R, but it doesn't behave as you describe. All 8 pins seem to work independently.

Here's a pic of both, with the modified Commlite CM-EF-EOSR ARC on the right:

Commlite CM-EF-EOS R (left) and Commlite CM-EF-EOSR ARC with casting ridge filed down to fit RF 1.4x (right).

You can see that the standard adapter would need major surgery to fit the RF 1.4x, but the ARC version only needed minor mods.

And here is the finished product:

Modified Commlite CM-EF-EOSR ARC mated with RF 1.4x.

This can fit any EF lens now. I've mated it with the EF 24-105 f/4L II and EF 100mm f/2 and it seems to work OK. But like with the TC stack, the R5 reports the RF 1.4x, but it doesn't multiply the FL by 1.4x:

Sample image with R5 + EF100mm f/2 USM + EXTENDER RF1.4x. Note R5 still reports FL as 100mm.

Interesting. That leaves three possibilities I can think of. Either yours is a newer version, mine is missing the springs or mine is fake. If the pins didn't touch at all, I'd lean towards the second, but yours is likely just 2. gen version.

It's nice to see that in the ARC version the flex ribbons did not need to be exposed as they were in mine.

Bigger wrote:

J.K.T. wrote:

Bigger wrote:

Yes, with the control ring. All 8 pins seem to have independent springs, and the force seems comparable to Canon lenses (but I didn't attempt to measure this). The adjacent pins didn't move.

OK - then it better than mine. As it seems also easier to mod (less material to remove), I'll have to get one of those. Disassembly is likely not an option, though.

I also have the Commlite CM-EF-EOS R, but I can't find it at the moment. If I locate it, I'll check it and report back later.

That would be nice - thanks!

I found the Commlite CM-EF-EOS R, but it doesn't behave as you describe. All 8 pins seem to work independently.

Here's a pic of both, with the modified Commlite CM-EF-EOSR ARC on the right:

Commlite CM-EF-EOS R (left) and Commlite CM-EF-EOSR ARC with casting ridge filed down to fit RF 1.4x (right).

You can see that the standard adapter would need major surgery to fit the RF 1.4x, but the ARC version only needed minor mods.

And here is the finished product:

Modified Commlite CM-EF-EOSR ARC mated with RF 1.4x.

This can fit any EF lens now. I've mated it with the EF 24-105 f/4L II and EF 100mm f/2 and it seems to work OK. But like with the TC stack, the R5 reports the RF 1.4x, but it doesn't multiply the FL by 1.4x:

Sample image with R5 + EF100mm f/2 USM + EXTENDER RF1.4x. Note R5 still reports FL as 100mm.

Very nice! I've taken optics out of good MC7 vintage Kiron teleconverters and mounted them into digital EF extension tubes, to make Canon EF non-reporting TCs:

https://www.dpreview.com/forums/post/64824180

I've also found that a Kenko Canon AF (EF) C-AF Teleplus SHQ 1.5x teleconverter, which has 5 elements instead of the usual 4, works extremely well with the Canon EF-S 55-250 IS STM, with the teleconverter's electronics removed to make it pass-through electronics:

https://www.dpreview.com/forums/post/65293237

The teleconverters are transparent to the camera, they just report the lens mounted on the teleconverters, even when stacked. Everything works including autofocus and image stabilization. The Kenko SHQ is optically very good with very little change in sharpness or CA. The Canon M6ii seems to be able to work with the TCs down to about f16 or so, it has very good low-light performance, however diffraction starts to noticeably degrade images by f11.

Larry Rexley wrote:

The teleconverters are transparent to the camera, they just report the lens mounted on the teleconverters, even when stacked. Everything works including autofocus and image stabilization.

The teleconverters are not completely transparent for the R5/R6. They need to know the FL to do proper IBIS. So, the fact that the R5 can't multiply FL by the RF TC ratio could affect IBIS coordination. Probably won't make a big difference with a great white lens since most IS is done in the lens. But could be an issue if you adapt a shorter lens.

With the EF teleconverters, they just report the attached lens to the body, but only for one TC. The second, stacked EF TC is invisible to the body. For the RF TC, this is not the case. The body can see both, but the R5 camera firmware doesn't account for them in the FL calculation.

A little help please. I have the 1.4 MII and 2x MIII. I'm missing something because it feals like I would be forcing it were I were to stack them.

Edit.  Ok, I went back and see it now.  I guess I need an adapter but really I should first upgrade the 1.4 MII.

PhotosFlight wrote:

A little help please. I have the 1.4 MII and 2x MIII. I'm missing something because it feals like I would be forcing it were I were to stack them.

The EF 1.4x II is not as sharp (optically) as and EF 1.4x III Extender because it's an older design that was produced for pre-digital lenses.  Adding one to an EF 2x Mk III Extender would result in (A) softening of the image from the EF 1.4x III Extender and (B) a further reduction of contrast and loss of image resolving due to the longer focal length of the 2x Extender being coupled with it.  We do get more actual magnification from stacking two extenders together but there's a cost.  The trade-off is in the amount of light lost and the optical consequences of putting too many glass elements between the subject and the sensor.

Edit. Ok, I went back and see it now. I guess I need an adapter but really I should first upgrade the 1.4 MII.

Canon wanted to discourage people from double-stacking Extenders.  Canon expressly DO NOT recommend double stacking Extenders because doing so results in poor contrast which in turn affects exposure and focus.  But of course, people kept doing it. 
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So Canon redesigned the Mk III Extenders (which are designed for Digital cameras and modern lenses) to prevent it.  Part of the optical redesign to improve image quality resulted in a slight increase in the front element and this required a rubber buffer to prevent people from damaging the rear optics of lenses that were not designed to accommodate an extender.  Many lens buyers don't realize that extenders will only fit on a select number of lenses so they try to cram them onto anything they want, often severely damaging their expensive lens in the process.
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Older Mk II Extender can be stacked together but the optical quality is markedly inferior due to an older optical and mechanical design, older optical coatings and a slower microprocessor.  These were pre-digital Extenders that were released to service lenses made between the 1980s and the 1990s.  For more recent Mk III Extenders, an EF12 (tele-tube) needs to be placed between the two Mk III Extenders to allow them to safely connect.  Note that Canon still do not recommend double-stacking Extenders.
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* Tip:  Most owners of Mk III Extenders don't realize that the lens caps for the front end have been redesigned ever so slightly to accommodate the slightly longer protrusion of the front optical element.  Getting the front end lens cap mixed up with your other lens caps will result in not being able to safely seat the front lens cap on a Mk III Extender if you grab the wrong one and attempt to remove an extender from a lens whilst in the field.

Marco Nero wrote:

PhotosFlight wrote:

A little help please. I have the 1.4 MII and 2x MIII. I'm missing something because it feals like I would be forcing it were I were to stack them.

The EF 1.4x II is not as sharp (optically) as and EF 1.4x III Extender because it's an older design that was produced for pre-digital lenses. Adding one to an EF 2x Mk III Extender would result in (A) softening of the image from the EF 1.4x III Extender and (B) a further reduction of contrast and loss of image resolving due to the longer focal length of the 2x Extender being coupled with it. We do get more actual magnification from stacking two extenders together but there's a cost. The trade-off is in the amount of light lost and the optical consequences of putting too many glass elements between the subject and the sensor.

Technically the light is not lost, it's just spread out over more pixels, or photo-buckets, if you will. So, the buckets still collect essentially the same number of photons, but each one has fewer photons in it. Each pixel is noisier, but when you take them together in scale, the overall image is not noisier.

The converter increases the focal length, and therefore the aperture ratio (f/number), but the overall aperture is the same. The diameter of the optical tube doesn't change, so the same flow of photons from the subject are captured.

The trade-off is whether the extra glass hurts more than the extra pixels help.

Bigger wrote:

Marco Nero wrote:

PhotosFlight wrote:

A little help please. I have the 1.4 MII and 2x MIII. I'm missing something because it feals like I would be forcing it were I were to stack them.

The EF 1.4x II is not as sharp (optically) as and EF 1.4x III Extender because it's an older design that was produced for pre-digital lenses. Adding one to an EF 2x Mk III Extender would result in (A) softening of the image from the EF 1.4x III Extender and (B) a further reduction of contrast and loss of image resolving due to the longer focal length of the 2x Extender being coupled with it. We do get more actual magnification from stacking two extenders together but there's a cost. The trade-off is in the amount of light lost and the optical consequences of putting too many glass elements between the subject and the sensor.

Technically the light is not lost, it's just spread out over more pixels, or photo-buckets, if you will. So, the buckets still collect essentially the same number of photons, but each one has fewer photons in it. Each pixel is noisier, but when you take them together in scale, the overall image is not noisier.

Well, there's less light filling the light-wells of each photoreceptor, hence there's less light reaching the sensor (hence the reason I used the term "less light"). By using two extenders on say the EF 100-400mm f/4.5-5.6L II lens, you end up going from a lens that has a narrow aperture of f/5.6 at 400mm to getting an aperture of f/13 (the camera seems to round it down from f/15.68) - which is a significant loss of light hitting the sensor. This forces us to use slower shutter speeds and higher ISO settings, both of which contribute to noise, which results in less detail. If you just use this same lens with a 2x Extender you'll be starting with f/11.
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Some cameras have larger light wells than others. The EOS R6 (for example) has a larger pixel size than the R5, so it's slightly better at gathering light, hence the much wider extended ISO range from that model of camera. The difference between Full Frame and APS-C sensors is much the same in that Full Frame sensors tend to have larger light-wells.
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From the Canon White Paper on Full Frame sensors (which probably needs an update).

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But not all is lost. By shooting at slightly higher ISO settings, we can often capture details missed with a shorter exposure using lower ISO settings. Oddly enough, higher ISO settings can often capture subtle elements in an image missed otherwise.

The converter increases the focal length, and therefore the aperture ratio (f/number), but the overall aperture is the same. The diameter of the optical tube doesn't change, so the same flow of photons from the subject are captured.

Adding Extenders acts like a "choke" on the amount of light racing down the barrel and hitting the sensor. The extra elements reduce the intensity of the light so that the image being focused onto the sensor is slightly dimmer and less intense.

The trade-off is whether the extra glass hurts more than the extra pixels help.

There's a fine line there. It depends on the recipe behind the extra glass. Modern optical coatings can redirect light from the peripheral edges of the optical elements to keep it from creating Coma where the glass itself is thinner towards the edges. And modern coatings can increase light transmission to a small degree. Canon claims they used their finest optical-grade glass when they created the Mk III Extenders and they also claim no detail was spared with their Spectra coatings for ghosting and flare (which are simply a revised version of their 1980s coatings)... and Fluorine coatings to increase light transmission (compared to previous coatings) whilst repelling dust and oils and enabling the lens element on the Extenders to be cleaned without solvents or liquids.
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There are times when you may wish for more magnification to increase perceived or visible details. An example is the moon. You can's see any crater shadows or related details with the naked eye. Or with a 3x (77mm) zoom lens. But you sure can when longer focal lengths are used. The greater the magnification, the more your light transmission to the sensor drops. Add extenders and you cut down on the light even further. And you can calculate it quite easily using the magnification of the Extenders. A 400mm lens which offers f/5.6 x 1.4 = f/8 (7.84).   The camera will round the aperture up or down slightly.

Marco Nero wrote:

Bigger wrote:

Marco Nero wrote:

PhotosFlight wrote:

A little help please. I have the 1.4 MII and 2x MIII. I'm missing something because it feals like I would be forcing it were I were to stack them.

The EF 1.4x II is not as sharp (optically) as and EF 1.4x III Extender because it's an older design that was produced for pre-digital lenses. Adding one to an EF 2x Mk III Extender would result in (A) softening of the image from the EF 1.4x III Extender and (B) a further reduction of contrast and loss of image resolving due to the longer focal length of the 2x Extender being coupled with it. We do get more actual magnification from stacking two extenders together but there's a cost. The trade-off is in the amount of light lost and the optical consequences of putting too many glass elements between the subject and the sensor.

Technically the light is not lost, it's just spread out over more pixels, or photo-buckets, if you will. So, the buckets still collect essentially the same number of photons, but each one has fewer photons in it. Each pixel is noisier, but when you take them together in scale, the overall image is not noisier.

Well, there's less light filling the light-wells of each photoreceptor, hence there's less light reaching the sensor (hence the reason I used the term "less light"). By using two extenders on say the EF 100-400mm f/4.5-5.6L II lens, you end up going from a lens that has a narrow aperture of f/5.6 at 400mm to getting an aperture of f/13 (the camera seems to round it down from f/15.68) - which is a significant loss of light hitting the sensor. This forces us to use slower shutter speeds and higher ISO settings, both of which contribute to noise, which results in less detail. If you just use this same lens with a 2x Extender you'll be starting with f/11.
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Some cameras have larger light wells than others. The EOS R6 (for example) has a larger pixel size than the R5, so it's slightly better at gathering light, hence the much wider extended ISO range from that model of camera. The difference between Full Frame and APS-C sensors is much the same in that Full Frame sensors tend to have larger light-wells.
.

From the Canon White Paper on Full Frame sensors (which probably needs an update).

.
But not all is lost. By shooting at slightly higher ISO settings, we can often capture details missed with a shorter exposure using lower ISO settings. Oddly enough, higher ISO settings can often capture subtle elements in an image missed otherwise.

The converter increases the focal length, and therefore the aperture ratio (f/number), but the overall aperture is the same. The diameter of the optical tube doesn't change, so the same flow of photons from the subject are captured.

Adding Extenders acts like a "choke" on the amount of light racing down the barrel and hitting the sensor. The extra elements reduce the intensity of the light so that the image being focused onto the sensor is slightly dimmer and less intense.

The trade-off is whether the extra glass hurts more than the extra pixels help.

There's a fine line there. It depends on the recipe behind the extra glass. Modern optical coatings can redirect light from the peripheral edges of the optical elements to keep it from creating Coma where the glass itself is thinner towards the edges. And modern coatings can increase light transmission to a small degree. Canon claims they used their finest optical-grade glass when they created the Mk III Extenders and they also claim no detail was spared with their Spectra coatings for ghosting and flare (which are simply a revised version of their 1980s coatings)... and Fluorine coatings to increase light transmission (compared to previous coatings) whilst repelling dust and oils and enabling the lens element on the Extenders to be cleaned without solvents or liquids.
.
There are times when you may wish for more magnification to increase perceived or visible details. An example is the moon. You can's see any crater shadows or related details with the naked eye. Or with a 3x (77mm) zoom lens. But you sure can when longer focal lengths are used. The greater the magnification, the more your light transmission to the sensor drops. Add extenders and you cut down on the light even further. And you can calculate it quite easily using the magnification of the Extenders. A 400mm lens which offers f/5.6 x 1.4 = f/8 (7.84). The camera will round the aperture up or down slightly.

Yes, but what I was trying to clarify was that the same amount of light is hitting the front element, the tele-extender just spreads it out over more pixels. Whether you crop the image in post, or crop it in camera with a tele-extender, you still have the same amount of usable light, and the same amount of lost light--the only light that is lost is the light that is cropped out (ignoring the small light loss in the tele extender air/glass). So, you are correct that less light hits the sensor, but that doesn't matter because we will be using more of the sensor area in the final image.

For practical purposes, final image noise doesn't depend on how many pixels you break that fixed amount of light up into. With more pixels, each pixel is noisier, but since there are more of them, it averages out in the end.

The change in aperture ratio (f/number) is not really relevant when you are cropping the image, only the aperture area is, and that doesn't change. So yes, the f/number goes up with a tele-extender, and you need to increase ISO (keeping ss constant). That increases noise per pixel, but you have more pixels, so overall image noise is roughly the same.

Bigger wrote:

Yes, but what I was trying to clarify was that the same amount of light is hitting the front element, the tele-extender just spreads it out over more pixels. Whether you crop the image in post, or crop it in camera with a tele-extender, you still have the same amount of usable light, and the same amount of lost light--the only light that is lost is the light that is cropped out (ignoring the small light loss in the tele extender air/glass). So, you are correct that less light hits the sensor, but that doesn't matter because we will be using more of the sensor area in the final image.

For practical purposes, final image noise doesn't depend on how many pixels you break that fixed amount of light up into. With more pixels, each pixel is noisier, but since there are more of them, it averages out in the end.

The change in aperture ratio (f/number) is not really relevant when you are cropping the image, only the aperture area is, and that doesn't change. So yes, the f/number goes up with a tele-extender, and you need to increase ISO (keeping ss constant). That increases noise per pixel, but you have more pixels, so overall image noise is roughly the same.

The more glass (lens elements) the light has to go through, the more scattering occurs within the glass and at the boundaries. This reduces the sharpness of the image and reduces the contrast of the overall image, washing the image out and wiping out detail.

Once you get beyond 20 or so elements of glass in the total light path, there doesn't seem to be much benefit in the added magnification --- the image is too degraded.

Also, stacking teleconverters may bring you pretty quickly to the diffraction limit of the configuration, and diffraction will also wash out detail and contrast.

Light transmission of lenses is also not 100%, for lenses and teleconverters it is reasonable to assume 10-20% of the light is reduced by the glass and the air-glass interfaces. This multiples, so stacking a couple teleconverters with a lens with a lot of elements/groups could reduce light transmission by as much as 50%.

Larry Rexley wrote:

Bigger wrote:

Yes, but what I was trying to clarify was that the same amount of light is hitting the front element, the tele-extender just spreads it out over more pixels. Whether you crop the image in post, or crop it in camera with a tele-extender, you still have the same amount of usable light, and the same amount of lost light--the only light that is lost is the light that is cropped out (ignoring the small light loss in the tele extender air/glass). So, you are correct that less light hits the sensor, but that doesn't matter because we will be using more of the sensor area in the final image.

For practical purposes, final image noise doesn't depend on how many pixels you break that fixed amount of light up into. With more pixels, each pixel is noisier, but since there are more of them, it averages out in the end.

The change in aperture ratio (f/number) is not really relevant when you are cropping the image, only the aperture area is, and that doesn't change. So yes, the f/number goes up with a tele-extender, and you need to increase ISO (keeping ss constant). That increases noise per pixel, but you have more pixels, so overall image noise is roughly the same.

The more glass (lens elements) the light has to go through, the more scattering occurs within the glass and at the boundaries. This reduces the sharpness of the image and reduces the contrast of the overall image, washing the image out and wiping out detail.

True, but spreading the image over more pixels increases the apparent sharpness of the sensor, which counteracts the loss in optical sharpness. Final IQ is a tradeoff between these opposing forces. The optimal configuration matches the lens resolution to the sensor resolution, and that could be none, one or two TC depending on the combo. So, an R6 could use an extra 1.4x TC over an R5, for example.

Once you get beyond 20 or so elements of glass in the total light path, there doesn't seem to be much benefit in the added magnification --- the image is too degraded.

That's an arbitrary rule of thumb. It depends on what type of elements (especially whether they are simple or compound) and coatings, as well as the base lens magnification and the added teleconverter magnification. So, more or less elements could be better, depending on the situation.

Also, stacking teleconverters may bring you pretty quickly to the diffraction limit of the configuration, and diffraction will also wash out detail and contrast.

The diffraction "limit" is not a hard limit at all. Yes, diffraction will also degrade the image similar to scattering above. But the point of diminishing returns in final IQ is often beyond the supposed diffraction limit. If you are cropping the image, then the limiting factor is the aperture area (i.e. front element diameter), not the aperture ratio.

Light transmission of lenses is also not 100%, for lenses and teleconverters it is reasonable to assume 10-20% of the light is reduced by the glass and the air-glass interfaces. This multiples, so stacking a couple teleconverters with a lens with a lot of elements/groups could reduce light transmission by as much as 50%.

I disagree with this framing. Yes, there is some light loss in the extra elements of the teleconverter(s), but they are fewer and thinner than the elements in the base lens, so this is a relatively small issue. I doubt that even stacked TC would reduce the light transmission by 50%, i.e. an extra f/stop.