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Question: similarities and differences between pancake/APO/prime lens?

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Old Monday 14th January 2019, 07:57   #1
vd Berg
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Question: similarities and differences between pancake/APO/prime lens?

Hello,

I digiscope for idenfication purpose. ‘tac sharp’ photos are not intended. For digiscoped identification purpose the performance of the telescope, camera, pancake/apochromat/prime lens and the achievable settings are relevant with regards to the birds size, contrast, weather conditions and distance towards the bird. As far I know a Digidapter © with telescope sleeve, Sigma/Zeiss/Voigtlander pancake lens can’t be rented in Europe.

Can you explain, why the camera’s aperture can be set to the widest open aperture of a pancake lens (Sigma/Zeiss/Voigtländer f/1.8, 2.0, 2.8, etc.), whilst the camera’s aperture must be set to the Swarovski rigs aperture (~f/8 to f12) when using a Swarovski TLS APO 23, 30, 43mm?

Does or doesn’t have the Swarovski TLS APO an aperture?

(Why) works a Swarovski TLS APO, yes or no, the same as a pancake lens (Sigma/Zeiss/Voigtländer f/1.8, 2.0, 2.8, etc.) with regard to the camera’s aperture, achieving better camera metering, gaining lower shutter speed and ISO, without losing depth of field when using a pancake lens?

With kind regards, vd Berg
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Old Tuesday 15th January 2019, 17:42   #2
SteveClifton
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Quote:
Originally Posted by vd Berg View Post
Hello,

I digiscope for idenfication purpose. ‘tac sharp’ photos are not intended. For digiscoped identification purpose the performance of the telescope, camera, pancake/apochromat/prime lens and the achievable settings are relevant with regards to the birds size, contrast, weather conditions and distance towards the bird. As far I know a Digidapter © with telescope sleeve, Sigma/Zeiss/Voigtlander pancake lens can’t be rented in Europe.

Can you explain, why the camera’s aperture can be set to the widest open aperture of a pancake lens (Sigma/Zeiss/Voigtländer f/1.8, 2.0, 2.8, etc.), whilst the camera’s aperture must be set to the Swarovski rigs aperture (~f/8 to f12) when using a Swarovski TLS APO 23, 30, 43mm?

Does or doesn’t have the Swarovski TLS APO an aperture?

(Why) works a Swarovski TLS APO, yes or no, the same as a pancake lens (Sigma/Zeiss/Voigtländer f/1.8, 2.0, 2.8, etc.) with regard to the camera’s aperture, achieving better camera metering, gaining lower shutter speed and ISO, without losing depth of field when using a pancake lens?

With kind regards, vd Berg
As far as I know the Swaro apo adapters are just simple pancake lenses with an adapter sleeve permanently built around them. There is no mechanism to alter either focus or aperture with the adapter. The aperture of the scope is fixed too, but will alter as you zoom the eyepiece. This mirrors the fact that many camera lenses also reduce aperture as you zoom in.

With a pancake lens attached to your camera instead of the Swaro Apo adapter, you obviously maintain the ability to change aperture and focus, though it is generally better to use the scope's focuser to reduce strain on the lens's focus motor.

I've read that using the widest lens aperture won't give any benefits in terms of shutter speeds beyond a certain optimum for the scope (let's say f4 or f5.6 for example) but in practice I see faster shutter speeds when using my Canon 40mm f2.8 wide open.

As the aperture of the scope is fixed I can see no way to control depth of field, except that it will be greater when lower focal lengths are used, and smaller when higher focal lengths are used (i.e. at maximum zoom)

Lastly, as far as I know the Swaro adapters have no electronic connections to the camera, hence why the camera should be set to 'shoot without lens'.

Last edited by SteveClifton : Tuesday 15th January 2019 at 17:54.
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Old Tuesday 15th January 2019, 20:04   #3
vd Berg
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Do you use/did you compare a pancake, APO and/or prime lens for digiscoping?

As far as I know an APO lens aperture is f12.

A digiscoper wrote “when using a pancake lens, switch the aperture to maximum opening f1.8, 2.0, 2.8, then better camera metering and faster shutter speed and lower ISO can be gained, without losing depth of field”.

Two other digiscopers wrote “an APO has (around 1-stop) less light as with a pancake lens”. One of former digiscopers wrote “I find a Digidapter © very good and stable”. The other of former digiscopers wrote “a Digidapter © can be fiddly and a slight knock can cause mis-alignment and vignetting of your image”

Yet another digiscoper wrote “the photo result for the APO, pancake, prime lens are about the same”.

Can you confirm former advantages of a pancake lens?
Can you confirm former same photo result from a pancake, APO prime lens?
Unclear is why/if former advantages of a pancake lens, are insufficient/not visible in the photo result due to, for example, the effective focal length and aperture of the rig and/or due to, for example, (constrained or incorrect) camera settings? Former camera settings constrained by the effective focal length and aperture of the rig and by the pancake/APO/prime lens!
Do you experienced an explanation for former why/if?

With kind regards,
vd Berg
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Old Saturday 26th January 2019, 15:33   #4
vd Berg
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Hello,

Facebook link about "comparing pancake, APO and prime lenses for digiscoping" https://www.facebook.com/nic.nam.372...14669566281575

Why are APO and pancake lens photo results are about the same, whilst pancake lenses have better aperture then APO AND for pancake lenses better camera metering and faster shutter speed and lower ISO can be gained?

...

With kind regards,
vd Berg
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