Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
11-29-2012, 10:56 AM   #16
Pentaxian
Just1MoreDave's Avatar

Join Date: Feb 2007
Location: Aurora, CO
Photos: Gallery | Albums
Posts: 4,814
If only actual focal length matters, the DA* 55/1.4 was a mistake. I give the lens designers credit for knowing more about this than me.

Besides the technical issues of certain focal lengths, the relationship with your subject is different at 5 feet than it is at 15 feet.

11-29-2012, 10:56 AM   #17
Pentaxian




Join Date: Jan 2012
Location: Slovenia
Posts: 2,141
The OP brings up an interesting point. If we focus (lol) on the 'flattering/unflattering' properties of focal lengths, we discover that the most used lenses are short to medium telephotos on FF.

Food for thought: There was a thread somewhere about "normal" lenses, and I got a lot of flak for saying that 28 (or whatever) mm's are not really that normal on APS-C because of barrel distortion. Now answer this: On a Q, a "replacement" for the classic portrait lens would have a FL of 15mm. What if you used a 15mm fisheye?
11-29-2012, 11:50 AM - 1 Like   #18
Site Supporter




Join Date: Mar 2010
Location: SW Washington
Posts: 814
Perspective is a function of camera distance only, nothing else. Focal length, whether true or "equivalent", has no direct effect on perspective.

Now if you're concerned about having the same framing with the same perspective, obviously "equivalent" focal length is the one that matters, as you would be standing in the same spot at "equivalent" FLs. True focal length is entirely irrelevant as far as perspective goes.
11-29-2012, 05:42 PM   #19
HSV
Veteran Member




Join Date: Sep 2012
Location: Texas
Posts: 321
Original Poster
Thanks to y'all for the input. I agree and understand that there's a relationship between distance, FL, framing, and distortion.

Let me see if I'm understanding this...let's say that you put a 50mm lens on a m4/3 body and a100mm lens on a FF body. If both are placed at the same distance from the subject, then the results will be equal? (in terms of unflattering distortion) How about putting a DA15 on a Q, and a FA85 on a FF?

I'm putting the example with the DA15 because it doesn't have much "native" distortion. Would (potentially) this mean that every lens can be a so-called portrait lens if I'm willing to crop? (without regards to other factors like DOF, resolving power, sharpness, noise, etc.)

Would this apply also to Giklab's fisheye example?

11-29-2012, 05:57 PM   #20
Veteran Member




Join Date: Apr 2011
Location: California
Photos: Gallery
Posts: 1,354
QuoteOriginally posted by HSV Quote
Let me see if I'm understanding this...let's say that you put a 50mm lens on a m4/3 body and a100mm lens on a FF body. If both are placed at the same distance from the subject, then the results will be equal?
Yes, this is correct. At least, it is theoretically correct (often what manufacturers list as focal length is not exactly precise).

QuoteOriginally posted by HSV Quote
this mean that every lens can be a so-called portrait lens if I'm willing to crop? (without regards to other factors like DOF, resolving power, sharpness, noise, etc.)
Yes, you are correct, again. But that is very theoretical, and you would need to overlook most of the properties of lenses and sensors in order to operate in that manner.

One thing I have found helpful is to actually think in terms of field of view. I.e., when you look at something (from wherever you are), crop an image of it in your mind. Pay attention to what is in the crop (in your mind). Then, move closer or farther from the object, and do the same thing. You will notice the difference.
11-29-2012, 06:12 PM   #21
HSV
Veteran Member




Join Date: Sep 2012
Location: Texas
Posts: 321
Original Poster
Thanks for the clarification.

Just curious, how about the "compression effect"? Does this also depend on distance or there's a true correlation to focal length?

I would assume that this one should be correlated to true focal length.
11-29-2012, 06:39 PM   #22
Veteran Member
Ikarus's Avatar

Join Date: Apr 2010
Location: California
Photos: Albums
Posts: 460
QuoteOriginally posted by HSV Quote
Thanks for the clarification.

Just curious, how about the "compression effect"?
Same thing. That's just what everybody was referring to by 'perspective (distortion)'. It's what flattens or elongates the face in these portrait shots that Eastman already pointed to above.
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!
distortion, equivalent, ff, k-mount, length, logic, pentax lens, portrait, slr lens, sort, topic
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Case Logic SLRC-205 fit K5? billylh Ask B&H Photo! 2 01-14-2012 09:44 PM
Subject height on a soccer field at 300mm FL vs position dosdan Photography Articles 3 12-16-2011 10:09 PM
AF vs MF logic and accuracy alvarossorio Pentax SLR Lens Discussion 11 07-27-2011 10:14 AM
Critique My Lens Logic les3547 Pentax SLR Lens Discussion 17 03-18-2011 11:45 PM
DA 55-300mm vs DA* 60-250mm: FL question Loren E Pentax SLR Lens Discussion 8 01-18-2011 06:39 PM



All times are GMT -7. The time now is 08:50 PM. | See also: NikonForums.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