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F-stop query - search not working
If I add a filter which loses 1 stop of light.....

On a fixed aperture setting how much would the shuter speed decrease?.

Does it slow down by a percentage - IE. 50%Or does it drop a set amount, like 1/40th..

So fo example if the previous shutter speed had been 1/100, would the new speed now be 1/60th? (or 40% maybe).

Also on a dslr system will a 1x4 multiplier lens (which apparently loses 1 stop) cause any vignetting?.

Any advice on this appreciated thank you..

Adrian.

Not updated for years, but...http://www.t1000.co.uk/photography.htm..

Comments (18)

Adrian Harris wrote:.

If I add a filter which loses 1 stop of light.....

One "stop" is (in this instance) one-half the light..

On a fixed aperture setting how much would the shuter speed decrease?.

50%...except there is no such thing as a "shutter speed". The correct term is "exposure time". The exposure time would double to compensate for adding a filter which absorbs one-half the light..

Also on a dslr system will a 1x4 multiplier lens (which apparentlyloses 1 stop) cause any vignetting?.

I think you mean a 1.4X teleconverter lens? Yes a 1.4X TC reduces the "speed" of the lens by one stop. BTW, a 2.0X TC reduces it 2 stops..

Charlie DavisNikon 5700, Sony R1, Nikon D300HomePage: http://www.1derful.infoBridge Blog: http://www.here-ugo.com/BridgeBlog/..

Comment #1

Adrian Harris wrote:.

If I add a filter which loses 1 stop of light.....

On a fixed aperture setting how much would the shuter speed decrease?.

You will double your time, since you loose 1/2 your light..

Does it slow down by a percentage - IE. 50%Or does it drop a set amount, like 1/40th..

It slows down by a percentage. One stop is double the time..

So fo example if the previous shutter speed had been 1/100, would thenew speed now be 1/60th? (or 40% maybe).

For 1/100, loosing a stop would make it 1/50..

Also on a dslr system will a 1x4 multiplier lens (which apparentlyloses 1 stop) cause any vignetting?.

I have not heard of a 1.4x extender (commonly called a TC/teleconverter) causing vignetting. A 1.4x extender will cause you to loose a stop, and generally degrades the optics of the lens a little bit (how much depends on how good the lens and the extender are)...

Comment #2

I suppose questions like this used to be simpler to answer when everything was controlled by purely mechanical dials and controls..

The starting point is the term "stop" which you used in relation to the filter. This means the filter reduced the amount of light by 50%..

To continue, older cameras would have a mechanical dial with the shutter speeds arranged in a single stop sequence, like this:.

1/500 - 1/250 - 1/125 - 1/60 - 1/30 - 1/15 - 1/8 - 1/4 and so on. Similarly the lens aperture would have a dial marked with the sequence such as f/16 - f/11 - f/8 - f/5.6 - f/4 - f/2.8 and so on..

With such a camera the answer to the question becomes easy, if the filter loses one stop of light, you simply adjust either the shutter or aperture by one stop to compensate..

It may seem confusing for a beginner presented with a modern camera where not only these traditional apertures and speeds are displayed, but also the intermediate values too. Also with a digital camera, there is another option, adjust the ISO.The relationship of all the above is illustrated on this page:http://www.dpreview.com/learn/?/Glossary/Exposure/Exposure_01.htmHope this helps,Peter..

Comment #3

Dave, it's not a matter of tight or loose...

Comment #4

Thanks to you all for really marvelous answers..

I think for me the key figure here was learning that a 'stop less' was equal to 50% reduction in light. Everything else now regarding shutter speed / exposure time, now falls into place..

For your interest: I had actually tried using a 1x4 'add on' teleconverter (which screws on the front of the lens) on the end of my 500mm f6.3 sigma zoom. The light levels were so poor even at highish ISO, the sutter speed was down around 1/80th second - producing very poor (well absolutely aweful really) hand held shots even with the 'anti-shake' device on (yes what do I expect at a focal length equiv of around 1000mm hand held - but one has to try!!).

Many thanks to all - for once more inceasing my understanding of the technicalities..

Back to the tripod ;o).

Adrian.

Not updated for years, but...http://www.t1000.co.uk/photography.htm..

Comment #5

Adrian Harris wrote:.

Thanks to you all for really marvelous answers..

Shux...thanks..

For your interest: I had actually tried using a 1x4 'add on'teleconverter (which screws on the front of the lens) on the end ofmy 500mm f6.3 sigma zoom..

I still believe that is was a "1.4X". .

However, I assumed it was a behind-the-lens TC...I think everybody else did too..

It must have been a terrible TC! First, a front-mounted TC will have to be HUGE to not affect the "speed" of the lens. Since you report that it gathered a lot less light, it must have been small. My estimate is that a proper 1.4X front TC for that lens would be about 80mm in diameter and add 3" to the total length..

The light levels were so poor even athighish ISO, the sutter speed was down around 1/80th second -producing very poor (well absolutely aweful really) hand held shotseven with the 'anti-shake' device on (yes what do I expect at a focallength equiv of around 1000mm hand held - but one has to try!!).

It would take a 2X TC to reach 1000mm. A 1.4TC gives 700mm..

A better, smaller, cheaper TC would be the Sigma APO 1.4X..

Charlie DavisNikon 5700, Sony R1, Nikon D300HomePage: http://www.1derful.infoBridge Blog: http://www.here-ugo.com/BridgeBlog/..

Comment #6

Chuxter wrote:.

50%...except there is no such thing as a "shutter speed". The correctterm is "exposure time". The exposure time would double to compensatefor adding a filter which absorbs one-half the light..

The correct term is shutter speed. It appears in every camera manual and a Google search will give endless hits. A better description however is "exposure time"..

To the OP to fill in a couple of small gaps a stop either halves or doubles the amount of light using either the shutter or the aperture to achieve that effect. To a DSLR set on anything other than manual the effect of the filter is transparent. The metering takes account of the reduced light through the filter..

Chris Elliott.

*Nikon* D Eighty + Fifty - Other equipment in Profile.

Http://PlacidoD.Zenfolio.com/..

Comment #7

Chris Elliott wrote:.

Chuxter wrote:.

50%...except there is no such thing as a "shutter speed". The correctterm is "exposure time". The exposure time would double to compensatefor adding a filter which absorbs one-half the light..

The correct term is shutter speed. It appears in every camera manualand a Google search will give endless hits. A better descriptionhowever is "exposure time"..

My point was that the term "shutter speed" is an oxymoron, since the unit of measure is time, not velocity. I see that you agree with me. .

To the OP to fill in a couple of small gaps a stop either halves ordoubles the amount of light using either the shutter or the apertureto achieve that effect..

Sensitivity can also be said to affect the exposure in units of "stops"..

Note that "stops" is a relative measure. EV also has a granularity of 1/2 or 2, but it is an absolute measure..

Charlie DavisNikon 5700, Sony R1, Nikon D300HomePage: http://www.1derful.infoBridge Blog: http://www.here-ugo.com/BridgeBlog/..

Comment #8

Hi Charlie.

Chuxter wrote:.

Adrian Harris wrote:.

Thanks to you all for really marvelous answers..

Shux...thanks..

For your interest: I had actually tried using a 1x4 'add on'teleconverter (which screws on the front of the lens) on the end ofmy 500mm f6.3 sigma zoom..

I still believe that is was a "1.4X". .

However, I assumed it was a behind-the-lens TC...I think everybodyelse did too..

It must have been a terrible TC! First, a front-mounted TC will haveto be HUGE to not affect the "speed" of the lens. Since you reportthat it gathered a lot less light, it must have been small. Myestimate is that a proper 1.4X front TC for that lens would be about80mm in diameter and add 3" to the total length..

My thinking went like this: The front mounted 1.4x teleconverter didn't cause any vignetting at full zoom - and because the fron piece of glass was almost twice the size of the rear lens on the converter - and therefore capable of catching much more light (something that a normal dslr style TC can not do), I assumed (hoped) I would get no light loss!!.

The light levels were so poor even athighish ISO, the sutter speed was down around 1/80th second -producing very poor (well absolutely aweful really) hand held shotseven with the 'anti-shake' device on (yes what do I expect at a focallength equiv of around 1000mm hand held - but one has to try!!).

It would take a 2X TC to reach 1000mm. A 1.4TC gives 700mm..

Because of the crop factor on my camera the 500mm sigma is equivalent of about 750mm - so with the 1.4x on it it does work out to just over 1000mm..

A better, smaller, cheaper TC would be the Sigma APO 1.4X..

Yes you are right and I shall possibly be looking for a good make..

The reason I tried a front mounted one - besides having a very high quality one around - was because the 500m lens has a max aperture at full zoom of f6 .3, dropping this a stop in low light means the camera auto focus doesnt work - and I knew through experiments that a normal 1.4x would not be good in this respect!!!.

I was hoping a front mounted TC would gather lots more light - and hence not drop a stop - and therefore be my saviour..

Out of interest, using a Raynox 2.2x converter on the front of my minolta A2 does in fact cause no light loss, due to the principal I have ried to describe..

Oh well, back to the drawing board..

Adrian.

Charlie DavisNikon 5700, Sony R1, Nikon D300HomePage: http://www.1derful.infoBridge Blog: http://www.here-ugo.com/BridgeBlog/.

Adrian.

Not updated for years, but...http://www.t1000.co.uk/photography.htm..

Comment #9

Adrian Harris wrote:.

Hi Charlie.

Chuxter wrote:.

Adrian Harris wrote:.

Thanks to you all for really marvelous answers..

Shux...thanks..

For your interest: I had actually tried using a 1x4 'add on'teleconverter (which screws on the front of the lens) on the end ofmy 500mm f6.3 sigma zoom..

I still believe that is was a "1.4X". .

However, I assumed it was a behind-the-lens TC...I think everybodyelse did too..

It must have been a terrible TC! First, a front-mounted TC will haveto be HUGE to not affect the "speed" of the lens. Since you reportthat it gathered a lot less light, it must have been small. Myestimate is that a proper 1.4X front TC for that lens would be about80mm in diameter and add 3" to the total length..

My thinking went like this: The front mounted 1.4x teleconverterdidn't cause any vignetting at full zoom - and because the fron pieceof glass was almost twice the size of the rear lens on the converter- and therefore capable of catching much more light (something that anormal dslr style TC can not do), I assumed (hoped) I would get nolight loss!!.

Yes, that's the way they are supposed to work! The front-mounted TC should not change the speed of the primary lens..

The light levels were so poor even athighish ISO, the sutter speed was down around 1/80th second -producing very poor (well absolutely aweful really) hand held shotseven with the 'anti-shake' device on (yes what do I expect at a focallength equiv of around 1000mm hand held - but one has to try!!).

But as you lengthen a lens it becomes more difficult to work with..

It would take a 2X TC to reach 1000mm. A 1.4TC gives 700mm..

Because of the crop factor on my camera the 500mm sigma is equivalentof about 750mm - so with the 1.4x on it it does work out to just over1000mm..

Nah. It's still just a 700mm lens. That "equivalent" thing is silly..

A better, smaller, cheaper TC would be the Sigma APO 1.4X..

Yes you are right and I shall possibly be looking for a good make..

The reason I tried a front mounted one - besides having a very highquality one around - was because the 500m lens has a max aperture atfull zoom of f6 .3, dropping this a stop in low light means thecamera auto focus doesnt work - and I knew through experiments that anormal 1.4x would not be good in this respect!!!.

That's very true. A rear-mounted TC works best on a fast lens..

Charlie DavisNikon 5700, Sony R1, Nikon D300HomePage: http://www.1derful.infoBridge Blog: http://www.here-ugo.com/BridgeBlog/..

Comment #10

Chuxter wrote:.

Because of the crop factor on my camera the 500mm sigma is equivalentof about 750mm - so with the 1.4x on it it does work out to just over1000mm..

Nah. It's still just a 700mm lens. That "equivalent" thing is silly..

Yes, it's still a 700mm lens (a 500mm w/ a 1.4x TC), but I wouldn't call the "equivalent" thing (aka crop factor) "silly." It comes in handy if you want to equate the same FoV for both a crop DSLR and a film SLR. It also comes in handy when using the 1/focal hand held rule of thumb...

Comment #11

Dave_s93 wrote:.

Chuxter wrote:.

Because of the crop factor on my camera the 500mm sigma is equivalentof about 750mm - so with the 1.4x on it it does work out to just over1000mm..

Nah. It's still just a 700mm lens. That "equivalent" thing is silly..

Yes, it's still a 700mm lens (a 500mm w/ a 1.4x TC), but I wouldn'tcall the "equivalent" thing (aka crop factor) "silly." It comes inhandy if you want to equate the same FoV for both a crop DSLR and afilm SLR. It also comes in handy when using the 1/focal hand heldrule of thumb..

I actually find the 'equivalent thing' very handy - as it gives me a good idea of how close I need to be - to try and get a reasonably sized photo of something..

One of my favourite devices at home is a Fuji F11 digicam attached to a x10 pair of binoculars. The F11 zooms from around 35mm to 105mm (equiv), so I know that this setup at half zoom, works out 'similar-ish' to the 500mm zoom on the 1.5 crop factored dslr. - if that makes any sense ;o).

Which meant when trying to develop a setup for nature photography, I had some sort of guide of what was needed..

I realise that for portrait type work much of this is possibly irrelevant..

I am not after much ...all I want is a 'perfect' setup :o).

One day....one day!!.

Adrian.

Not updated for years, but...http://www.t1000.co.uk/photography.htm..

Comment #12

I'm sorry to be so blunt, but both you and Dave are just silly about this. There is nothing special about the FF 35mm format that should render IT the reference for all other formats. The proper way is to accept the format you are using and develop heuristic insights into how various actual FL lenses will perform..

Back when we had REAL cameras, when I picked up my Minox, I did not have to reference it to my 8x10 view camera. They were simply different formats and each had different uses...each had different FL lenses. We didn't need mental pablum to help us cope with the differences. .

To be honest, I sorta enjoy being blunt....

Charlie DavisNikon 5700, Sony R1, Nikon D300HomePage: http://www.1derful.infoBridge Blog: http://www.here-ugo.com/BridgeBlog/..

Comment #13

Chuxter wrote:.

To be honest, I sorta enjoy being blunt....

Really, Chaz?!? I'd never have guessed!! .

But, blunt or not, you are right..

As soon as people manage to think in terms of the various f-lengths working on the formats they are using, instead of some format they may previously have used, but are NOT CURRENTLY using... the ... ummm .. better [?].

Now, the whole idea of NEW photographers learning the equivalent effects of f-lengths on a format they have HAVE NEVER used, and likely never will .....

(sharp intake of breath).

... strikes me as utterly bizarre, and I just cannot understand why it is still happening at this stage in the development of digital image formats. !! Regards,Baz..

Comment #14

Barrie Davis wrote:.

... strikes me as utterly bizarre, and I just cannot understand whyit is still happening at this stage in the development of digitalimage formats. !! .

A couple of reasons. One, there are still a wide variety of different digital formats, maybe experts are conversant with all of them, but the casual photographer may not be. Even if the common language turns out to be something like Esperanto, an artificial creation..

The second reason is that many manufacturers actually label their camera bodies and lenses with the 35 mm equivalents, and quote this in all the literature. Sometimes you have to dig deep into the appendix at the back of the manual to try to find the true focal length. While I'm on the subject, did you ever try to find what the smallest aperture setting of a camera is? In some cases it seems to be a secret and is not openly published even in the specifications. Now that is bizarre.Regards,Peter..

Comment #15

As a relative newbee to the DSLR, I am still amazed at all this talk about crop factors and equivalent focal lengths. A 50mm lens is a 50mm lens. Although I have used an SLR for over forty years, I can still get distracted by the hype. I took some portraits to test some lighting the other day with the kit lens at 55mm. I actually thought that they would look like they were taken with a 90mm lens. Duh, they looked like they were taken with a 55mm lens..

David..

Comment #16

Chuxter wrote:.

I'm sorry to be so blunt, but both you and Dave are just silly aboutthis. There is nothing special about the FF 35mm format that shouldrender IT the reference for all other formats. The proper way is toaccept the format you are using and develop heuristic insights intohow various actual FL lenses will perform..

Well, since I currently shoot with the Canon system, they currently have 3 different sensor sizes: APS-C, APS-H, and FF (1.6x, 1.3x, and 1.0x). Even your Nikon system has two different sizes DX and FX (1.5x and 1.0x). It helps me to know what lenses I will need if I decide to upgrade to a camera body with a different size sensor..

Also, most people are familiar with the 1/focal rule of thumb (yes, it is different for everyone depending on how steady they are, hence the rule of thumb) for 35mm. If you were using a 4/3rds system, you need to know that you have to multiply it by 2, but if you were using an APS sensor, you need to multiply it by 1.5 (for Nikon) or 1.6 (for Canon) to apply it to your DSLR..

Another case is if someone says "I get blurry pics with a 50mm lens, but I keep my shutter speed at 1/60 and I am fairly steady, what do you think it is?" Do you not think it is important to know the crop factor to rule out camera shake?.

Also, as you know (after our previous discussion), DoF is also dependent on sensor size. If you want to calculate DoF, you need to know the crop factor of your DSLR...

Comment #17

Barrie Davis wrote:.

Chuxter wrote:.

To be honest, I sorta enjoy being blunt....

Really, Chaz?!? I'd never have guessed!! .

But, blunt or not, you are right..

Sometimes, to be provocative (which is my REAL goal), it helps to speak directly..

As soon as people manage to think in terms of the various f-lengthsworking on the formats they are using, instead of some format theymay previously have used, but are NOT CURRENTLY using... the ... ummm.. better [?].

Now, the whole idea of NEW photographers learning the equivalenteffects of f-lengths on a format they have HAVE NEVER used, andlikely never will .....

(sharp intake of breath).

... strikes me as utterly bizarre, and I just cannot understand whyit is still happening at this stage in the development of digitalimage formats. !! .

Yep...I don't get it either? And it's like people who do this seem ready to fight to the death defending their correctness..

Charlie DavisNikon 5700, Sony R1, Nikon D300HomePage: http://www.1derful.infoBridge Blog: http://www.here-ugo.com/BridgeBlog/..

Comment #18

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