Need Info on Lens

uppi_777 · 01-23-2018, 05:47 AM

I am very new to Cameras but now my passion is growing up day by day
I would like to capture some pictures/Videos in the span of this area. My field is 100m length and 3.5m width the ratio would be 100m/3.5m = 28.5714mm
Now i am very much interested if someone could let me know how to find focal length and which lens can i use to cover my field.
On the other hand i would like to know at what length there is a high sharpness of the camera in 100m length. Could some one explain with drawings are by theory

**WPRESTO** · 01-23-2018, 07:20 AM

I'm not sure I fully understand the question, so let me try to analyze what I think you're asking:

1) you want to photograph something that is 3.5 meters wide;
2) you want to photograph it from a distance of 100 meters (camera to subject distance = 100 meters).

Is that correct?

ASSUMING that you want a 3.5 meter field of view at a distance of 100 meters, the best fit lens would be 600mm on APS-C. However, any lens of 300mm up to 600mm will provide an image that covers a bit more, but which could be cropped slightly down to a 3.5 meters wide field of view. Among current Pentax lenses the following would be good choices:

1) DA 300mm f4
2) DA 300mm f4 + 1.4X teleconverter
3) DA 150~450mm
4) DA 150~450mm + 1.4X teleconverter

If you go to legacy equipment (=no longer manufactured) there are many more choices, perhaps too many for me to list, although other Pentaxians may recommend their favorite older telephoto lens of 300 to 600mm. By far the best would be the FA 600mm f4, but even used that will cost you $5000. If you really want one, and can afford it, there's one for sale on the Pentax Equipment For Sale thread (click Buy/Sell above).

Adam · 01-23-2018, 09:13 AM

Originally posted by uppi_777

I am very new to Cameras but now my passion is growing up day by day
I would like to capture some pictures/Videos in the span of this area. My field is 100m length and 3.5m width the ratio would be 100m/3.5m = 28.5714mm
Now i am very much interested if someone could let me know how to find focal length and which lens can i use to cover my field.
On the other hand i would like to know at what length there is a high sharpness of the camera in 100m length. Could some one explain with drawings are by theory

This may help:

Field of View Tables, APS-C, 24x36, 645D, 645, 6x7 - PentaxForums.com

The yellow column is APS-C, next one is full frame.

**mikesbike** · 01-24-2018, 05:39 PM

More information is needed. In addition to (1) the size of the area you intend to cover, the other factors that must be considered are (2) the distance to this area from which you will be positioned, (3) what kind of subject matter will take place within those boundaries, and (4) very importantly, what type and degree of lighting will be present.

Virtually all DSLR cameras are capable as far as these factors are concerned, some more so than others- especially regarding the last two. The property of which lens you will select to go onto the camera is of vital importance to all 4 factors. Also to be more specific, which model camera will you be using?

Last edited by mikesbike; 01-24-2018 at 09:08 PM.

01-23-2018, 05:47 AM	#1
uppi_777 New Member Join Date: Jan 2018 Posts: 1	Need Info on Lens I am very new to Cameras but now my passion is growing up day by day I would like to capture some pictures/Videos in the span of this area. My field is 100m length and 3.5m width the ratio would be 100m/3.5m = 28.5714mm Now i am very much interested if someone could let me know how to find focal length and which lens can i use to cover my field. On the other hand i would like to know at what length there is a high sharpness of the camera in 100m length. Could some one explain with drawings are by theory

01-23-2018, 07:20 AM	#2
WPRESTO Loyal Site Supporter Join Date: Aug 2010 Location: Massachusetts Photos: Gallery \| Albums Posts: 59,138	I'm not sure I fully understand the question, so let me try to analyze what I think you're asking: 1) you want to photograph something that is 3.5 meters wide; 2) you want to photograph it from a distance of 100 meters (camera to subject distance = 100 meters). Is that correct? ASSUMING that you want a 3.5 meter field of view at a distance of 100 meters, the best fit lens would be 600mm on APS-C. However, any lens of 300mm up to 600mm will provide an image that covers a bit more, but which could be cropped slightly down to a 3.5 meters wide field of view. Among current Pentax lenses the following would be good choices: 1) DA 300mm f4 2) DA 300mm f4 + 1.4X teleconverter 3) DA 150~450mm 4) DA 150~450mm + 1.4X teleconverter If you go to legacy equipment (=no longer manufactured) there are many more choices, perhaps too many for me to list, although other Pentaxians may recommend their favorite older telephoto lens of 300 to 600mm. By far the best would be the FA 600mm f4, but even used that will cost you $5000. If you really want one, and can afford it, there's one for sale on the Pentax Equipment For Sale thread (click Buy/Sell above). Last edited by WPRESTO; 01-23-2018 at 09:34 AM.

01-23-2018, 09:13 AM	#3
Adam Administrator Site Webmaster Join Date: Sep 2006 Location: Arizona Photos: Gallery \| Albums Posts: 51,608	Originally posted by uppi_777 I am very new to Cameras but now my passion is growing up day by day I would like to capture some pictures/Videos in the span of this area. My field is 100m length and 3.5m width the ratio would be 100m/3.5m = 28.5714mm Now i am very much interested if someone could let me know how to find focal length and which lens can i use to cover my field. On the other hand i would like to know at what length there is a high sharpness of the camera in 100m length. Could some one explain with drawings are by theory This may help: Field of View Tables, APS-C, 24x36, 645D, 645, 6x7 - PentaxForums.com The yellow column is APS-C, next one is full frame. Adam PentaxForums.com Webmaster (Site Usage Guide \| Site Help \| My Photography) PentaxForums.com server and development costs are user-supported. You can help cover these costs by donating or purchasing one of our Pentax eBooks. Or, buy your photo gear from our affiliates, Adorama, B&H Photo, KEH, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

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01-24-2018, 05:39 PM	#4
mikesbike Site Supporter Join Date: Dec 2016 Location: Southeastern Michigan Posts: 4,561	More information is needed. In addition to (1) the size of the area you intend to cover, the other factors that must be considered are (2) the distance to this area from which you will be positioned, (3) what kind of subject matter will take place within those boundaries, and (4) very importantly, what type and degree of lighting will be present. Virtually all DSLR cameras are capable as far as these factors are concerned, some more so than others- especially regarding the last two. The property of which lens you will select to go onto the camera is of vital importance to all 4 factors. Also to be more specific, which model camera will you be using? Last edited by mikesbike; 01-24-2018 at 09:08 PM.