very unscientific test

[dean messenger]

removed because as usual the forum bully boys decide to get pathetically personal
think some people need to get off there arse and spend some time with there cameras rather than sit on here all day having digs at people and making personal comments

 

[snerkler]

Yep, that's one hell of a 'zoom'. Not sure I could cope with the softness of the image with the TC on though. How does a shot taken at 960mm cropped to the same FOV compare?

 

[dean messenger]

these are SOOC exported from LR with no adjustments straight to jpeg. plus i didnt use mirror lock up so there may be some small vibration from the shutter. i think if i increased ISO, dropped the manfrotto 190 x pro 3 legs downa section, kicked in mirror lock up and had a little fiddle with manual focusing could probably get a pretty sharp shot.
the 1.4 TC only arrived this afternoon so these are about as basic a test as you can get without making to many adjustments .certainly for £68 for the TC and the lens costing if you look around under £700 other than a bridge camera you arent going to get even close to that distance for the money .
dont think i will be catching birds in flight but set up correctly in a hide or static location for wildlife i think some sharp results could be had

 

[snerkler]

these are SOOC exported from LR with no adjustments straight to jpeg. plus i didnt use mirror lock up so there may be some small vibration from the shutter. i think if i increased ISO, dropped the manfrotto 190 x pro 3 legs downa section, kicked in mirror lock up and had a little fiddle with manual focusing could probably get a pretty sharp shot.
the 1.4 TC only arrived this afternoon so these are about as basic a test as you can get without making to many adjustments .certainly for £68 for the TC and the lens costing if you look around under £700 other than a bridge camera you arent going to get even close to that distance for the money .
dont think i will be catching birds in flight but set up correctly in a hide or static location for wildlife i think some sharp results could be had

No I agree, if you need that reach then it's far better than a bridge etc. Would be interested to see how sharp it is with TC when you've got used to it then as I've just ordered this lens. I'd imagine it's 'fun' trying handheld at that FL

 

[dean messenger]

ive shot handheld down to 1/8th of a second with this beast!! that was without the tc of course lol. think id be pushing my luck then . still sensibly i think you can quite happily shoot at 1/250th handheld with no problems the vibration control is very good in it

 

[Phil V]

Just one observation, the TC does lose you a stop, but isn't reporting it. You've even told us that there's a change in shutter speed required when you added the TC in the same conditions.

 

[dean messenger]

Just one observation, the TC does lose you a stop, but isn't reporting it. You've even told us that there's a change in shutter speed required when you added the TC in the same conditions.

yes but theres also a change in shutter speed from the 85mm to the 150-600mm
longer lens less light slower speed. sounds pretty normal to me. if i put the 150-600 at 150 it has a faster speed than at the 600 end, so with the TC its changing the speed again.
and second test shows the DOF changing when shot at same speed and ISO and just making an aperture change from F/6.3 to f/8 shooting test shots of my daughter at f .3 the background is very blurred with shallow dof, at the f 8 the background becomes clearer.

obviously i would need to do some proper test shots through the range shooting at a slide ruler at 45 degrees to see if at any point there is no change in the aperture adjustment because surely if its starting at 6.3 then for the first 1-2 stops they should be the same until it corrects itself.

 

[Phil V]

yes but theres also a change in shutter speed from the 85mm to the 150-600mm
longer lens less light slower speed. sounds pretty normal to me. if i put the 150-600 at 150 it has a faster speed than at the 600 end, so with the TC its changing the speed again.
and second test shows the DOF changing when shot at same speed and ISO and just making an aperture change from F/6.3 to f/8 shooting test shots of my daughter at f .3 the background is very blurred with shallow dof, at the f 8 the background becomes clearer.

obviously i would need to do some proper test shots through the range shooting at a slide ruler at 45 degrees to see if at any point there is no change in the aperture adjustment because surely if its starting at 6.3 then for the first 1-2 stops they should be the same until it corrects itself.

No, the change of settings from the shorter lenses is down to the amount of sky you were metering with those.

It should be obvious to you that the 1.4 TC loses a stop of light. Given that the focal length changes but the physical size of the aperture doesn't (you appreciate that's how it works?).

A Canon TC is chipped so that the camera knows it's there so reports an adjusted aperture, other TCs without a chip just take the aperture info from the lens and report it to the camera. Meanwhile the camera is just metering the light coming through the lens, whether the aperture is mis-reported or not isn't important, it won't stop anything working properly. The bonus of course is that with a Canon TC the AF could refuse to try with some camera / lens combinations. The downside is that with those combinations a camera will try to AF in conditions where there'll not be enough contrast for it to be efficient.

Are you certain you understand this photography lark enough to be doing testing?

 

[Canon Bob]

......Given that the focal length changes but the physical size of the aperture doesn't (you appreciate that's how it works?).

Don't forget that the lens is f/5 at the wider end and f/6.3 at the longer end, Phil

Bob

 

[dean messenger]

not sure what a canon TC has to do with anything as its as stated a kenko one
Are you certain you understand this photography lark enough to be commenting Phil
my point being that on a previous TC i had a few years back on a 5.6 lens i could not go below F8 on it in AP or even Manual.
maybe it was due to being acheaper TC and the communication worked different but its misleading when TC's report as losing 1 f stop, when you actually lose 1 stop of in effect shutter speed. i still get 6.3 with the TC , still get the same DOF, i just get it at a stop slower in terms of speed.
thats the point im perhaps badly trying to make.

 

[Nawty]

i still get 6.3 with the TC

No you don't. f/6.3 is the ratio of the physical size of the aperture compared to the focal length, if you increase the focal length (by adding a TC) and the physical size of the aperture doesn't get bigger (which it can't) then the aperture gets smaller (i.e. the number gets bigger).

 

[snerkler]

not sure what a canon TC has to do with anything as its as stated a kenko one
Are you certain you understand this photography lark enough to be commenting Phil
my point being that on a previous TC i had a few years back on a 5.6 lens i could not go below F8 on it in AP or even Manual.
maybe it was due to being acheaper TC and the communication worked different but its misleading when TC's report as losing 1 f stop, when you actually lose 1 stop of in effect shutter speed. i still get 6.3 with the TC , still get the same DOF, i just get it at a stop slower in terms of speed.
thats the point im perhaps badly trying to make.

If you're getting the same DOF it would suggest the aperture is stopping down as DOF alters with Focal length. If it was staying at f6.3 then DOF would be shallower with the TC. My guess it that the camera just isn't registering the correct aperture for some reason. What's the smallest aperture the 60D focuses at? Maybe this is something to do with it, and also why the last shot looks soft?

 

[Canon Bob]

...... i still get 6.3 with the TC , still get the same DOF, i just get it at a stop slower in terms of speed.
thats the point im perhaps badly trying to make.

You don't still get f/6.3 with the TC it just doesn't report the correct aperture and the 1 stop slower in speed is because the aperture is one stop slower

No you don't. f/6.3 is the ratio of the physical size of the aperture compared to the focal length,

It's not the "physical size of the aperture", it's the "apparent size of the aperture" when viewed through the object lens.

Bob

 

[dean messenger]

If you're getting the same DOF it would suggest the aperture is stopping down as DOF alters with Focal length. If it was staying at f6.3 then DOF would be shallower with the TC. My guess it that the camera just isn't registering the correct aperture for some reason. What's the smallest aperture the 60D focuses at? Maybe this is something to do with it, and also why the last shot looks soft?

60D 5.6 and centre is 2.8

according to a few other reviews of this TC it states it reports the correct aperture and lens / TC focal length and AF works in all focus modes from single point to all points
physical size wont change just because theres a TC on it though. a hole is a hole is a hole so the change is based on the length of the tube that has the hole at one end thus determining how much light gets to that hole or is required to meet a certain criteria so as bob states its apparent size and not physical change . further away ou are from the hole the smaller it appears to be. but in terms of communication between camera and body as far as the camera is concerned the hole at f6.3 is still f.6.3 no matter how long the tube part in front of it is.

as for the image being soft as i had already explained was a quick test shot and there is added effect of virbration caused by mirror bounce as well as a slow shutter speed..
as the title stated its by no means a scientific test but 4 snapshots showing the difference and the simple fact the 150-600 is working with a 1.4tc

 

[snerkler]

60D 5.6 and centre is 2.8

according to a few other reviews of this TC it states it reports the correct aperture and lens / TC focal length and AF works in all focus modes from single point to all points
physical size wont change just because theres a TC on it though. a hole is a hole is a hole so the change is based on the length of the tube that has the hole at one end thus determining how much light gets to that hole or is required to meet a certain criteria so as bob states its apparent size and not physical change . further away ou are from the hole the smaller it appears to be. but in terms of communication between camera and body as far as the camera is concerned the hole at f6.3 is still f.6.3 no matter how long the tube part in front of it is.

as for the image being soft as i had already explained was a quick test shot and there is added effect of virbration caused by mirror bounce as well as a slow shutter speed..
as the title stated its by no means a scientific test but 4 snapshots showing the difference and the simple fact the 150-600 is working with a 1.4tc

You're getting confused between f numbers, aperture, and physical aperture dimensions. F6.3 is a ratio so it absolutely matters "how long the tube part is". With a lens with a focal length of 24mm the physical size of the aperture at f6.3 will be much smaller than the physical size of the aperture of a 600mm lens at f6.3.

By the sounds of it then the smallest aperture your camera can focus at it f5.6, which will actually allow f6.3 in this case. With the TC this would stop it down to f9 but obviously your camera can't do this so maybe the software tricks it into thinking it's still f6.3 to allow the AF to work. I understand why you said the shot was soft, but all I meant is that this would also go some way to explaining it as the AF won't be as accurate.

 

[dean messenger]

in live view and using only centre focus point its 2.8 so should give slightly better results.
obviously the biggest issue with such stupidly long lengths is going to be the exaggerated movement , even the slightest fraction off mm lens bounced caused by vibration is going to have a serious effect.
im using the manfrotto 190 xpro 3 but only have the basic 3 way pan and tilt 804rc2 head which gives a bit of a wobble to say the least with this chunk of lens on it.
hopefully a much bigger head with better support will help things a little.

 

[LCPete]

Interesting thanks for posting yes it does get tricky when you start putting on TCs
I can manage to handhold my 300 2.8 when I put on a 1.4 TC and get great results but really struggle to get sharp shots with a X 2 converter
It's just my technique I'm sure but going to give it another go next week

 

[Nawty]

in live view and using only centre focus point its 2.8

Only if the lens allows it by being f/2.8 in the first place - which yours isn't.

 

[snerkler]

in live view and using only centre focus point its 2.8 so should give slightly better results.
obviously the biggest issue with such stupidly long lengths is going to be the exaggerated movement , even the slightest fraction off mm lens bounced caused by vibration is going to have a serious effect.
im using the manfrotto 190 xpro 3 but only have the basic 3 way pan and tilt 804rc2 head which gives a bit of a wobble to say the least with this chunk of lens on it.
hopefully a much bigger head with better support will help things a little.

Sorry to keep correcting you but a f2.8 sensor won't be more accurate in this case as it's only most accurate with lenses f2.8 and faster, smaller apertures than that it will not be as accurate. Normally what it means is that at f2.8 and faster it's cross type, smaller than this it's single line.

What you need to know is the smallest aperture you can have for AF to work, which you mentioned f5.6 earlier (which you can get away with f6.3 on most of the time). If you put slower lenses on such as f8 then it will essentially disable the camera AF. It is this why I think your camera registers f6.3 with TC on (even though it's actually f9) as if it thought it was a f9 lens it wouldn't work. Of course as it's 'tricking' the camera AF will be unreliable as there's not enough light hitting the AF module.

There are some cameras that can focus down to f8 and so this set up would be fine. It would be interesting to know if these register f8 (won't register f9 I wouldn't have thought ) or f6.3.

I'm not familiar with your camera though so it may indeed focus down to f8 in which case your AF should be fairly reliable with TC on and it's very strange why it still registers f6.3. Can anyone confirm what the smallest aperture the OP's camera will focus to?

But you are right that with the crazy focal length any tiny movement will be exaggerated and it could very well be just this that's causing softness.

 

[dean messenger]

i think you mean max aperture not smallest aperture. and on the 60D its listed as 3.5 according to website specs.
sadly what is missing from the 60D which would really help is the AF micro fine tune. such a shame they left that out as i think thats where the difference lies between getting that extra edge of sharpness and why the reults may end up on the slighlty soft side

 

[snerkler]

i think you mean max aperture not smallest aperture. and on the 60D its listed as 3.5 according to website specs

No, there is a smallest aperture (in terms of f-number) in which a camera will focus at as beyond this there's not enough light (according to the manufacturers) for the AF to work reliably. The smallest aperture won't be f3.5 otherwise you wouldn't even be able to use kit lenses.

 

[dean messenger]

No, there is a smallest aperture (in terms of f-number) in which a camera will focus at as beyond this there's not enough light (according to the manufacturers) for the AF to work reliably. The smallest aperture won't be f3.5 otherwise you wouldn't even be able to use kit lenses.

cant find that info anywhere, only talks about the widest aperture.
though the tamrons smallest is F/40 and i can still get focus lock with it on that .. also
the Tc states the following
Full AF operation with the TelePlus MC4 AF 1.4X is possible using camera lenses with open apertures of F4 or brighter

i tend not to stray above f/16 anyway so 99% of shooting is done between f/8 and f/16, only going wide on my 85mm f/1.8 down to around f/4 in mist cases.
beyond f/16 on the tamron you start to run the risk of diffraction

 

[petersmart]

With the stats you give you are ending up with a lens the equivalent of approx 1300mm ( 600mm x 1.6 x 1.4) therefore a rule of thumb would be that handheld you will need at least 1/1300 sec - personally even with IS I would opt for at least 1/2000 sec.

But an interesting experiment and I think you could quite easily use PP to increase the sharpness in the longest pics.
.

 

[boyfalldown]

though the tamrons smallest is F/40 and i can still get focus lock with it on that .. also

(D)SLRs only stop the aperture down when the shutter button is pressed. AF is done before then with the aperture open, so final f-stop is no guide to AF. If I recall the 60D doesn't AF well at apertures darker then f/5.6

 

[Nawty]

f/40 is not the widest aperture, it's the smallest and the lens only stops down to that when you press the shutter button.

So, if the WIDEST (i.e. Smallest number) aperture of your lens is f/6.3 (which it is at 600mm) then you AF system has to try and focus through the relative darkness of f/6.3.

It used to be the case that pretty much all AF modules worked at f/5.6 only and so putting a faster lens on didn't improve the sensitivity of the AF. Nowadays some work at wider apertures which should mean better AF in dark situations, in you case the camera will utilise fast lenses up to f/3.5. However this is only true if the lens has a maximum aperture of f/3.5. Your lens at 600mm has a maximum aperture of f/6.3 so you are not seeing this benefit.

 

[snerkler]

cant find that info anywhere, only talks about the widest aperture.
though the tamrons smallest is F/40 and i can still get focus lock with it on that .. also
the Tc states the following
Full AF operation with the TelePlus MC4 AF 1.4X is possible using camera lenses with open apertures of F4 or brighter

(D)SLRs only stop the aperture down when the shutter button is pressed. AF is done before then with the aperture open, so final f-stop is no guide to AF. If I recall the 60D doesn't AF well at apertures darker then f/5.6

f/40 is not the widest aperture, it's the smallest and the lens only stops down to that when you press the shutter button.

So, if the WIDEST (i.e. Smallest number) aperture of your lens is f/6.3 (which it is at 600mm) then you AF system has to try and focus through the relative darkness of f/6.3.

As above the aperture only stops down when the shutter is pressed. So if you have a f2.8 lens but stop it down to f22 the lens still focuses at f2.8 and the aperture blades only close down when the actual shot is taken.

The reason the TC probably states that is for the reasons I've been talking about. Most cameras could only focus with an aperture of F5.6 or wider, and adding a 1.4TC to a f4 lens makes it f5.6 (1.4 TC reduces the aperture by 1 stop). There are now cameras that can still focus at f8 so the TC's info needs updating really.

 

[Swanseajack]

cant find that info anywhere, only talks about the widest aperture.
though the tamrons smallest is F/40 and i can still get focus lock with it on that .. also
the Tc states the following
Full AF operation with the TelePlus MC4 AF 1.4X is possible using camera lenses with open apertures of F4 or brighter

i tend not to stray above f/16 anyway so 99% of shooting is done between f/8 and f/16, only going wide on my 85mm f/1.8 down to around f/4 in mist cases.
beyond f/16 on the tamron you start to run the risk of diffraction

The way I read the bold part I have highlighted, is the TC will AF with F4 lenses or quicker, i.e f2.8 lenses. So your Tamron shouldn't AF then?????

When I used my Kenko TC on a D7100 & Nikon 300mm f4 AFS lens during the winter months the TC wouldn't AF if it was a dark day due to rain etc..... When I looked at the Kenko site it states that MF only when lighting was poor. It wasn't that great when lighting was good on my setup. Others who have the same setup find the TC is comparable to the Nikon equivelant. Maybe due to batch varity?

Be nice try out in a hide where you can use you beanbag for stability, rather than the head you've got.

Thanks for posting, nice little quick test of the lens and TC.

 

[chris malcolm]

The point of an experimental test is to find out something. It's not at all clear to me what you want to find out. If you make the wrong assumptions about what the camera is doing then what you think you've discovered will be wrong. There are so many wrong assumptions in your discussions of what your camera is doing that I suggest that to start with you should stop doing autofocus and autoexposure. Then you will know what the camera is doing -- exactly what you told it to do.

Next you must decide what question you want your test to answer. If you're interested in the angle of view I suggest you stop thinking in terms of the very misleading "equivalent focal lengths" and simply consider the angle of view (amount of zoom) purely in terms of the angle, in degrees. For example at 600mm your camera probably has a field of view of 2-3 degrees. You can find web sites which will calculate the exact angle for you if you didn't do the trigonometry of lens imaging at school. If you are interested in comparative detail resolution of different lenses you must remove all other sources of detail blur, e.g. shoot using a remote shutter release or a timed delay on a tripod in bright light, and using careful manual focus. If your lens or camera has image stabilisation it should be turned off. Then you can compare that with your camera's autofocus, which you will have to experiment with to find out how it behaves under your chosen conditions.

Note that there are lots of very special techical problems associated with getting the best out of long lenses, sufficiently special that that there's an area of expertise called "long lens technique". Try strapping a laser pointer on your long lens with the camera on a tripod. Now watch the laser spot on a wall while you try various ways of firing the shutter without moving the laser dot.

 

[Canon Bob]

The way I read the bold part I have highlighted, is the TC will AF with F4 lenses or quicker, i.e f2.8 lenses. So your Tamron shouldn't AF then?????

The f/5.6 minimum aperture size is Canon's usual parlance as they don't have any slower lenses so there's nothing that falls between f/5.6 and f/8 (f/8 occurs with extenders). It would be more correct if they specified that AF is limited to apertures >f/8 rather than <f/5.6 but that would be helping to market third party slow telephotos.

Bob

 

[snerkler]

The way I read the bold part I have highlighted, is the TC will AF with F4 lenses or quicker, i.e f2.8 lenses. So your Tamron shouldn't AF then?????

Nope it shouldn't, which is why I think that the camera is saying that it's not stopping down when the TC is attached so it can trick it into working albiet not very accurately. For some reason f6.3 lenses still seem to work on cameras that state they can 'only' focus down to f5.6 and I think it's down to some jiggery pokery with the software

 

[Nawty]

It's down to available light and specifications, the manufacturers spec f/5.6 (for example) as that will work in most situations, that's not to say it won't work beyond that it's just out of spec (my old D700 would easily focus at f/8). Obviously if the conditions are super bright the the AF is more likely to work.

I doubt the TC is being intentionally clever, some kenko converters simply don't report they are there.

 

[dean messenger]

The point of an experimental test is to find out something. It's not at all clear to me what you want to find out. If you make the wrong assumptions about what the camera is doing then what you think you've discovered will be wrong. There are so many wrong assumptions in your discussions of what your camera is doing that I suggest that to start with you should stop doing autofocus and autoexposure. Then you will know what the camera is doing -- exactly what you told it to do.

Next you must decide what question you want your test to answer. If you're interested in the angle of view I suggest you stop thinking in terms of the very misleading "equivalent focal lengths" and simply consider the angle of view (amount of zoom) purely in terms of the angle, in degrees. For example at 600mm your camera probably has a field of view of 2-3 degrees. You can find web sites which will calculate the exact angle for you if you didn't do the trigonometry of lens imaging at school. If you are interested in comparative detail resolution of different lenses you must remove all other sources of detail blur, e.g. shoot using a remote shutter release or a timed delay on a tripod in bright light, and using careful manual focus. If your lens or camera has image stabilisation it should be turned off. Then you can compare that with your camera's autofocus, which you will have to experiment with to find out how it behaves under your chosen conditions.

Note that there are lots of very special technical problems associated with getting the best out of long lenses, sufficiently special that that there's an area of expertise called "long lens technique". Try strapping a laser pointer on your long lens with the camera on a tripod. Now watch the laser spot on a wall while you try various ways of firing the shutter without moving the laser dot.

the test was purely to compare the range between the different lenses from the 10mm and 85mm as reference to the 600mm and then the 600mm with the tc.
think your reading far to much into it.
and if you reread i never stated equiv focal lengths and clearly made the discernable difference of quoting field of view ( yes i do know the difference and no i dont need to study trig thanks all the same )
the same in regard to resolution that was notsomething that was being tested for. hence why the title clearly states totally unscientific test.
as for stopping doing AF or AE, sorry but who said i was doing AE in the first place and i took shots both AF and manual with the TC on. and yes i also shot in brght sunlight on a tripod with 10 second time for each shot. so i dont really see what any of your points are getting at tbh.
as for wrong assumptions. no they arent wrong assumptions, they are stated facts as to what the camera settings are displaying nothing more. i suggest you go back and read the very first post again and you will understand the nature of the test ( not experimental in the least ) and the whole idea behind it which was to determine if A: the TC will actually work at various Aperture settings ( yes it does ) and what extra magnification it is giving over the 600mm in real terms by way of a rather boring subject matter ( namely a sticker on a lamp post )

 

[HoppyUK]

Phase-detect AF works by comparing the image received through either side of the lens. As the f/number rises, the aperture becomes physically smaller and there comes a point when the two sides are too similar for the AF sensor to differentiate accurately. Canon calls a halt to proceedings over f/5.6 (with all but a few high end DSLRs that will run to f/8 ) and above that the AF simply switches off. Any lens or lens/telecon-combo that's above f/5.6 needs to fool the camera to keep the AF working, but that doesn't change the fact that the aperture is beyond the limit and performance is compromised. Some cameras continue to work reasonably well, while others are less good. As Bob says, no Canon lens has a maximum aperture higher than f/5.6.

Normal phase-detect AF can work in surprisingly low light, but needs good contrast, ie light/dark transitions and edges. It's worth noting though that the newer on-sensor phase-detect AF doesn't work so well in low light (at least, at the current stage of development). There's another step with Canon AF systems, when additional sensitivity on the AF sensor is activated at f/2.8 and lower f/numbers. Focusing is more accurate, and faster.

Contrast-detect AF in live view works at any f/number, and can be extremely accurate, but likes both good light and contrast.

 

[dean messenger]

Phase-detect AF works by comparing the image received through either side of the lens. As the f/number rises, the aperture becomes physically smaller and there comes a point when the two sides are too similar for the AF sensor to differentiate accurately. Canon calls a halt to proceedings over f/5.6 (with all but a few high end DSLRs that will run to f/8 ) and above that the AF simply switches off. Any lens or lens/telecon-combo that's above f/5.6 needs to fool the camera to keep the AF working, but that doesn't change the fact that the aperture is beyond the limit and performance is compromised. Some cameras continue to work reasonably well, while others are less good. As Bob says, no Canon lens has a maximum aperture higher than f/5.6.

Normal phase-detect AF can work in surprisingly low light, but needs good contrast, ie light/dark transitions and edges. It's worth noting though that the newer on-sensor phase-detect AF doesn't work so well in low light (at least, at the current stage of development). There's another step with Canon AF systems, when additional sensitivity on the AF sensor is activated at f/2.8 and lower f/numbers. Focusing is more accurate, and faster.

Contrast-detect AF in live view works at any f/number, and can be extremely accurate, but likes both good light and contrast.

not sure which canon high end cameras go higher but i know ive read of some issues with the 5D mk lll comobined with certain lenses / TC's , ( nothing to do with lens incompatibility ) and certain combos that will work on APS-C but not FF .
end of the day the whole thing was just some test shots to see how much extra reach i could get ( if the thing actually worked which it does ) over the 600mm . wasnt expecting a full blown debate on the matter but i guess thats forums for ya.
how much the TC will get used. very rarely most likely , pretty much limited to bright static location shots of wildlife, certainly not for any airshows as think there would be far to many issues ( hard enough to track at 600mm let alone adding an extra complication into the factor.

 

[snerkler]

Phase-detect AF works by comparing the image received through either side of the lens. As the f/number rises, the aperture becomes physically smaller and there comes a point when the two sides are too similar for the AF sensor to differentiate accurately.

That's interesting, and makes sense that this is the reason of aperture/image restriction rather than due to the light restriction tbh, as you say some cameras can AF down to -3ev which is obviously far less than you would get from a camera stopped down to f8 in bright sunshine.

 

[chris malcolm]

the test was purely to compare the range between the different lenses from the 10mm and 85mm as reference to the 600mm and then the 600mm with the tc.
think your reading far to much into it.
and if you reread i never stated equiv focal lengths and clearly made the discernable difference of quoting field of view ( yes i do know the difference and no i dont need to study trig thanks all the same )
the same in regard to resolution that was notsomething that was being tested for. hence why the title clearly states totally unscientific test.

OK, you're not concerned with resolution, just magnification.

as for stopping doing AF or AE, sorry but who said i was doing AE in the first place and i took shots both AF and manual with the TC on. and yes i also shot in brght sunlight on a tripod with 10 second time for each shot. so i dont really see what any of your points are getting at tbh.
as for wrong assumptions. no they arent wrong assumptions, they are stated facts as to what the camera settings are displaying nothing more.

True, but you made wrong assumptions about what they meant in your subsequent discussions with commenters.

i suggest you go back and read the very first post again and you will understand the nature of the test ( not experimental in the least )

Not experimental? You wanted to find something out, you tried a few different photographs to help you find out, noted down what you thought were the important parameters, and published the results for comment. That's an experiment.

and the whole idea behind it which was to determine if A: the TC will actually work at various Aperture settings ( yes it does ) and what extra magnification it is giving over the 600mm in real terms by way of a rather boring subject matter ( namely a sticker on a lamp post )

If you wanted to find out what extra magnification the TC gave all you needed to do was photograph a brick wall and count the bricks. The lesser number of bricks with the TC would have given you the extra magnification. But you say you wanted the extra magnification "in real terms" and are focusing your attention on a tiny bit of detail in the middle of the image, a printed label. In other words what you want to know is how much extra detail the TC gives you. A sensible concern given that some TCs with some lenses do of course magnify, but don't show you any more detail than you'd get by simply cropping the image without the TC. How much extra detail you get is called resolution. Which you started off by saying your non-experimental test was definitely not testing for.

That supports my earlier impression that you're too confused to have a sensible discussion about your non-experiment.

 

[Phil V]

not sure what a canon TC has to do with anything as its as stated a kenko one
Are you certain you understand this photography lark enough to be commenting Phil
...

I mentioned the Canon because it will correctly report the new aperture. Your Kenko one doesn't.
It seems (if you keep reading) that I do indeed know exactly what's happening - whereas...

...
maybe it was due to being acheaper TC and the communication worked different but its misleading when TC's report as losing 1 f stop, when you actually lose 1 stop of in effect shutter speed. i still get 6.3 with the TC , still get the same DOF, i just get it at a stop slower in terms of speed.
thats the point im perhaps badly trying to make.

Then your previous TC was chipped to report it's presence (like the Canon one), so it might have been cheaper than the Kenko - but it was more sophisticated

The stop you lose is aperture, (pick any one of the results - they'll all tell you the same thing)

All of that and I haven't owned a TC for 25 years, but when I did, the thing I noticed most was how much it made the viewfinder darker (maybe there's a clue in that)

 

[Phil V]

not sure which canon high end cameras go higher but i know ive read of some issues with the 5D mk lll comobined with certain lenses / TC's , ( nothing to do with lens incompatibility ) and certain combos that will work on APS-C but not FF .
end of the day the whole thing was just some test shots to see how much extra reach i could get ( if the thing actually worked which it does ) over the 600mm . wasnt expecting a full blown debate on the matter but i guess thats forums for ya.
how much the TC will get used. very rarely most likely , pretty much limited to bright static location shots of wildlife, certainly not for any airshows as think there would be far to many issues ( hard enough to track at 600mm let alone adding an extra complication into the factor.

Well you could have done a little research before you posted and showed you were clueless. Or you could have done some research after I told you the facts, but you chose to argue with me...

And now you're questioning the knowledge of the bloke who writes the tests

Of course it's possible you're the only person on this thread who knows what they're talking about... But I wouldn't bank on it.

 

[Goody13]

Is this not getting a bit picky. I'm all for being precise but, unless there is some previous history that I am unaware of, it seems to me that we have an enthusiastic OP who is now being chastised for pedantry reasons.

 

[Phil V]

Is this not getting a bit picky. I'm all for being precise but, unless there is some previous history that I am unaware of, it seems to me that we have an enthusiastic OP who is now being chastised for pedantry reasons.

Well...
He started it. He had the option of backing down, but he chose to argue

not sure what a canon TC has to do with anything as its as stated a kenko one
Are you certain you understand this photography lark enough to be commenting Phil
...