Image compression difference with teleconverter ... ?

[InTheSky]

Hello,

I was thinking about that in the Traffic to go to work (Montreal city is not easy to reach when you are working downtown and you need to be there in car ) of the difference of image compression from a Tele zoom focal lenght and the equivalent with a smaller zoom with a teleconverter.

Here is my point :

If I'm using a 400mm F/5.6 lens, and I'm focusing on a subject like at 20 meter with some elements in front and on the back of it, do i will get the same exact compression for the element in front and back or the subject if I'm using a 200mm F/2.8 with a 2x teleconverter . I'm thinking of a YES answer ... , but I'm just not sure at 100%. (in this example The camera is always at the same position from the subject).

I know that this is not like doing comparison between APS and Full frame like 300mm on FF and 200mm on APS because the subject distance will not be the same on different sensor size.

Thank you in advance,

Regards,

Frank

[David Kilpatrick]

Yes, you were right. It does not matter how the 400mm is created, the perspective effect is always the same from the same viewpoint.

You also get the same, exactly, with a 300mm on APS-C as you do with a 400mm on full frame, from the same position.

David

[bossel]

If I understand correctly, you would also get the same perpective (though it will be hard to see) using a 10mm lens. Perspective depends on your distance/position to the subject photographed. Using different focal lengths will just grab smaller or larger parts of the subject.

[InTheSky]

Yes, you were right. It does not matter how the 400mm is created, the perspective effect is always the same from the same viewpoint.

You also get the same, exactly, with a 300mm on APS-C as you do with a 400mm on full frame, from the same position.

David

In this case, the difference will only be the deep of field, meaning at F/5.6 on both lens, on the APS-C the deep of field will be bigger. Am I right ?

Regards,

Frank

[David Kilpatrick]

Right again. On APS-C, depth of field is about 1.5 stops more (nor exactly). Roughly speaking f6.3 or f7.1 will give you the same depth of field as f11 on the full frame with the same angle of view of lens.

David

[harvey]

I think it is more obvious if you consider angle of view which would be the same for the same equivalent focal length.