Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
01-10-2019, 07:18 AM   #1
Senior Member




Join Date: Aug 2017
Photos: Gallery
Posts: 118
Focal lenght and FOV in specific APS-C designed lens. Need explanation.

Is the FOV of lens specifficaly designed for APS-C camera the same as lens designed for FF? For example is FOV of SMC Pentax-DA* 55mm F1.4 SDM on APS-C the same as HD Pentax-D FA* 50mm F1.4 SDM AW on FF?

01-10-2019, 07:42 AM - 1 Like   #2
Loyal Site Supporter
Loyal Site Supporter
UncleVanya's Avatar

Join Date: Jul 2014
Photos: Gallery | Albums
Posts: 15,446
Lets pretend both are 50mm. So lets use the DA 50 f1.8 and the fa 50 f1.4.

The fact that It is desined for APSC or ff isn't what matters as far as field of view. The full frame lens will appear narrower in any APSC camera.

A way to think of it is if you have a 13x19 frame and picture and then add an 11x14 Matt directly over the image - the scene you see will look narrower. That's what happens then camera sensor isn't as large as the full frame lens covers so the image is cropoed on all sides. Some crop lenses can cover more than the bare minimum and can shoot respectable shots on a Full frame sensor with roughly the same angle of view that a full frame would have. Other crop lenses barely cover the APSC sensor and wouldn't be able to shoot a wider image But this is due to a lack of image sensor coverage.

---------- Post added 01-10-19 at 09:47 AM ----------

The take away should be the sensor size sets the angle of view for all lenses of a certain focal length. So even a 50mm 645 lens on APSC will give the same width angle of view as an APSC one. The only time this fails is when the lens can't cover the sensor because it is desined for an even smaller sensor.

Last edited by UncleVanya; 01-10-2019 at 07:48 AM.
01-10-2019, 08:18 AM   #3
Seeker of Knowledge
Loyal Site Supporter
aslyfox's Avatar

Join Date: Aug 2016
Location: Topeka, Kansas
Photos: Gallery | Albums
Posts: 14,818
I agree with UncleVanya

As I understand it, the focal length of a lens does not change regardless if you use it on a full sensor camera or a ASP-C camera

the FOV of the lens changes only because of the different size of the sensor and thus what part of the image is captured by the image:

" If you take a photo with a smaller sensor and the same lens it will only show a smaller area of the scene. "

Crop Factor Explained

_________________

Full Frame Sensor vs Crop Sensor: Which is Right For You?

_____________________

The Crop Factor Unmasked
Field of View vs Focal Length on various formats


Read more at: The Crop Factor Unmasked - Articles and Tips | PentaxForums.com
01-10-2019, 08:19 AM   #4
Pentaxian
photoptimist's Avatar

Join Date: Jul 2016
Photos: Albums
Posts: 3,539
QuoteOriginally posted by nobody Quote
Is the FOV of lens specifficaly designed for APS-C camera the same as lens designed for FF? For example is FOV of SMC Pentax-DA* 55mm F1.4 SDM on APS-C the same as HD Pentax-D FA* 50mm F1.4 SDM AW on FF?
The short answer is no. The FOV of SMC Pentax-DA* 55mm F1.4 SDM on APS-C will be much narrower than the FOV of the HD Pentax-D FA* 50mm F1.4 SDM AW on FF.

The longer answer depends on three facts:

First, the focal length of a lens is a geometric property of the lens and the lens alone. Focal length is entirely independent of the format of the camera it was designed for or the camera the lens is put on.

Second, the FOV of a particular lens on a particular camera is a function of both the focal length of the lens and the physical size of the sensor or film format size of the camera. For a given focal length, smaller formats have smaller FOVs. For a given format, longer focal lengths have smaller FOVs.

Third, a lens can have a "design FOV" which is the largest angular view that the lens is capable of producing without unacceptable softness and vignetting. This is the size of the image circle projected by the lens. A 50 mm DA lens might have a small image circle that does not cover a full frame sensor.

01-10-2019, 08:20 AM   #5
Site Supporter
Site Supporter
c.a.m's Avatar

Join Date: Jan 2013
Location: Ottawa, Canada
Photos: Gallery
Posts: 1,847
Edit: I was typing at the same time as @photoptimist!

@nobody, the 'field of view' (FOV) can refer to either a dimensional (e.g., feet, meters) or angular (degrees) measurement.

In general, a full frame camera gives a wider FOV than an APS-C format camera, for a given lens focal length.

Here are the horizontal angular fields of view for your cases:

DA* 55mm lens on an APS-C camera: 25 degrees.

D FA* 50mm lens on a FF camera: 40 degrees.

Certain lenses that are designed specifically for APS-C cameras do not provide the wider 'image circle' that is required by a full-frame camera. An example is the DA 15mm Limited lens -- its image circle won't cover the entire sensor on a K-1 camera, so its images show black corners on that camera.

- Craig

Last edited by c.a.m; 01-10-2019 at 05:59 PM. Reason: DA 15 clarification
01-10-2019, 08:27 AM   #6
Seeker of Knowledge
Loyal Site Supporter
aslyfox's Avatar

Join Date: Aug 2016
Location: Topeka, Kansas
Photos: Gallery | Albums
Posts: 14,818
QuoteOriginally posted by c.a.m Quote
. . . Certain lenses that are designed specifically for APS-C cameras do not provide the wider 'image circle' that is required by a full-frame camera. An example is the DA 15mm Limited lens -- it won't provide the necessary FOV on a K-1 camera, so its images show heavy vignetting on that camera.

- Craig
this might be of interest:


Full Frame Coverage of DA Lenses: Comprehensive Test
Which DA lenses cover the full 24x36 mm frame?


Read more at: Full Frame Coverage of DA Lenses: Comprehensive Test - Gear Guides | PentaxForums.com
01-10-2019, 09:23 AM   #7
Administrator
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 48,876
QuoteOriginally posted by nobody Quote
Is the FOV of lens specifficaly designed for APS-C camera the same as lens designed for FF? For example is FOV of SMC Pentax-DA* 55mm F1.4 SDM on APS-C the same as HD Pentax-D FA* 50mm F1.4 SDM AW on FF?
To put it simply: no. 55mm on APS-C gives you a 29.4 degree diagonal FoV, whereas 50mm on full frame gives you a (much wider) 46.8 degrees. Refer to the table below:



As a rule of thumb, if a lens has focal length f on APS-C, the same field of view would be achieved by a lens with focal length 1.5f on full frame (so in this case 55mm on APS-C would be comparable to ~83mm on FF). The format for which the lens was designed does not matter in this calculation.

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, buy your photo gear from our affiliates, Adorama, B&H Photo, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

01-10-2019, 10:38 AM   #8
Senior Member




Join Date: Aug 2017
Photos: Gallery
Posts: 118
Original Poster
QuoteOriginally posted by Adam Quote
As a rule of thumb, if a lens has focal length f on APS-C, the same field of view would be achieved by a lens with focal length 1.5f on full frame (so in this case 55mm on APS-C would be comparable to ~83mm on FF). The format for which the lens was designed does not matter in this calculation.
On one particular lens, I agree. But what if the lens is 50mm BUT is specifically designed for APS-C camera. Will FOV differ in comparison to FF lens on FF camera?

01-10-2019, 12:31 PM   #9
Administrator
Site Webmaster
Adam's Avatar

Join Date: Sep 2006
Location: Arizona
Photos: Gallery | Albums
Posts: 48,876
QuoteOriginally posted by nobody Quote
On one particular lens, I agree. But what if the lens is 50mm BUT is specifically designed for APS-C camera. Will FOV differ in comparison to FF lens on FF camera?
Inherently, no, the FOV would not differ. However, it's possible that the lens would not cover the FF image circle, and thus only be usable in APS-C mode, in which case the FOV would be reduced to whatever it is on APS-C. This is visualized in the third example below:


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, buy your photo gear from our affiliates, Adorama, B&H Photo, or Topaz Labs, and get FREE Marketplace access - click here to see how! Trusted Pentax retailers:

01-10-2019, 04:20 PM   #10
Pentaxian
photoptimist's Avatar

Join Date: Jul 2016
Photos: Albums
Posts: 3,539
QuoteOriginally posted by nobody Quote
On one particular lens, I agree. But what if the lens is 50mm BUT is specifically designed for APS-C camera. Will FOV differ in comparison to FF lens on FF camera?
A 50mm lens designed for APS-C put on a APS-C camera will have the identical FOV of a 50mm lens designed for FF but put on a APS-C camera.

A 50mm lens designed for APS-C put on a APS-C camera will have a smaller FOV than a 50mm lens designed for FF but put on a FF camera.

A 50mm lens designed for APS-C put on a APS-C camera may have a smaller FOV than that same 50mm lens designed for APS-C but put on a FF camera (if the image circle does not cover FF).
01-10-2019, 04:44 PM   #11
Pentaxian
swanlefitte's Avatar

Join Date: May 2015
Location: New Orleans
Photos: Gallery
Posts: 2,408
The only difference between a lens for ff and apsc is vignetting. The smaller sensor stays inside the vignetting where the vignetting will fall on the larger sensor.

So a lens designed for apsc projects an image too small for a ff sensor. It gives advantages in design such as size.
01-10-2019, 04:55 PM   #12
Pentaxian




Join Date: Dec 2016
Posts: 1,846
All good answers, but I like the short answers best. Any 50mm lens will have the same FOV on APS-C DSLR cameras, whether or not they were designed with FF or APS-C in mind. However, since those lenses designed for the smaller APS-C sensor will usually have the circumference of lens elements cut smaller, so the lens design can take advantage of the APS-C format to physically be smaller, this may result in darkening of the outer areas, especially corners, of images if the lens is used on a FF body.

Will FOV differ (if on APS-C cameras) compared to a FF lens on a FF camera? Yes. A 50mm lens on a FF body will have a wider FOV compared to having it on APS-C camera bodies. To have both the same FOV, for example, you need to have a lens of approximately 75mm (or 77mm) on a FF body to equal the FOV of a 50mm lens on APS-C bodies.

Last edited by mikesbike; 01-10-2019 at 05:10 PM.
01-10-2019, 05:01 PM   #13
Pentaxian
swanlefitte's Avatar

Join Date: May 2015
Location: New Orleans
Photos: Gallery
Posts: 2,408
QuoteOriginally posted by mikesbike Quote
All good answers, but I like the short answers.
My answer was shorted.
Yet our approach was the same.
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
50mm, angle, aps-c, apsc, camera, f1.4, ff, fov, frame, image, k-mount, lenght and fov, lens, lenses, pentax lens, sdm, sensor, slr lens, view
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
How to cheat ibis about focal lenght? pasorro Pentax DSLR Discussion 25 11-21-2018 10:48 AM
Custom input focal lenght for astrotracer irishbeachboy Pentax K-1 8 04-02-2018 01:59 PM
Setting proper focal lenght with K-1 and manual lenses Sylwester Pentax K-1 5 06-23-2016 03:46 AM
Macro Macro lens focal length variation and FOV images to compare? JayR Photographic Technique 2 02-04-2015 05:29 PM
manual lens macro focal lenght question Frank Bowler Troubleshooting and Beginner Help 5 12-10-2010 10:23 PM



All times are GMT -7. The time now is 11:14 PM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top