Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
01-17-2012, 11:17 AM   #2161
Oog
Forum Member




Join Date: Sep 2011
Posts: 86
Compression or the appearance of "compression" or expansion has something to do with distance ratios. Take a head and shoulders shot - one with your favorite 85mm, and one with 24mm, on your favorite 35mm film. **Move close with the 24mm to match subject size.** The face and nose appears flattened with the 85mm. The nose looks longer and the hairline appears to recede with the 24mm.

Why?

For 85mm, the distance ratio of nose to camera:hairline to camera is close to 1:1.
For 24mm, the distance ratio of nose to camera:hairline to camera is considerably less than 1:1

We would normally refer to this apparent lack of compression when using the 24mm in this case as "subject distortion" though that is relative. Go stare at someone's face from 3 inches away and you'll see "distortion" too.

(and yes, I got the concept of distance/perspective 15 years ago....)

01-17-2012, 11:29 AM   #2162
Veteran Member
Pentaxor's Avatar

Join Date: May 2009
Location: Vancouver, B.C.
Photos: Gallery
Posts: 6,513
QuoteOriginally posted by Oog Quote
Compression or the appearance of "compression" or expansion has something to do with distance ratios. Take a head and shoulders shot - one with your favorite 85mm, and one with 24mm, on your favorite 35mm film. **Move close with the 24mm to match subject size.** The face and nose appears flattened with the 85mm. The nose looks longer and the hairline appears to recede with the 24mm.

Why?

For 85mm, the distance ratio of nose to camera:hairline to camera is close to 1:1.
For 24mm, the distance ratio of nose to camera:hairline to camera is considerably less than 1:1

We would normally refer to this apparent lack of compression when using the 24mm in this case as "subject distortion."

(and yes, I got the concept of distance/perspective 15 years ago....)
with regards to the topic of equivalence, the only factor that would remain equal is exposure. f1.2 would still be f1.2 and f2.8 would still be f2.8 regardless of whatever camera size sensor the lens is fitted at.

trying to equal the other factors would result to compromises.

equaling the FOV would still result to DOF difference. cropping the image from two different lenses could lead to less resolution from the shorter focal length lens and would still show DOF difference. compression would take place if focus distance is made a compromise.

equaling the DOF would mean difference in focal length, which means loss of FOV flexibility when shooting or shooting distance flexibility.

we try so hard on trying to equate two different systems. I'm not saying it is not achievable. it is achievable, to a certain extent, but as of the moment, with the present lenses that are available and the nature of the lenses themselves, there will always be compromises involved.

there is no real and perfect equivalent lens like the FA31 for the APS-C. no equivalent for the 50/1.2. nor the 85/1.4. all these would result to compromises like FOV (cropping), DOF difference and compression (focus distance involved). again the only thing that doesn't change is exposure.

Last edited by Pentaxor; 01-17-2012 at 05:06 PM.
01-17-2012, 12:41 PM   #2163
Site Supporter
Aristophanes's Avatar

Join Date: Jul 2008
Location: Dartmouth, Nova Scotia
Photos: Albums
Posts: 3,790
QuoteOriginally posted by Pentaxor Quote
we try so hard on trying to equate two different systems. I'm not saying it is not achievable. it is achievable, to a certain extent...
Yes, but is it discernible?

That's the question.

We do look at photographs, right? The difference between f/5.6 on APS-C and f/8 on 35mm is hard to distinguish.

Going down a rabbit hole here.
01-17-2012, 12:53 PM   #2164
Loyal Site Supporter
eddie1960's Avatar

Join Date: Aug 2010
Location: Toronto
Photos: Gallery | Albums
Posts: 12,163
QuoteOriginally posted by Aristophanes Quote
Yes, but is it discernible?

That's the question.

We do look at photographs, right? The difference between f/5.6 on APS-C and f/8 on 35mm is hard to distinguish.

Going down a rabbit hole here.
You mean aside from the FOV difference of course which is pretty damn dramatic if you ask me.

and of course the difference in apparent compression ..... and all the other stuff argued in the last 4 or so pages.

I'm generally in Falks court in this discussion, personally i don't care who makes the camera but i think someone could build a better design than the existing models, and Pentax is great at getting the best out of a design and could well build a nicer FF than canikon do. If they made it as appealing as the K5 has been to canikon users then we may see more migration towards Pentax

01-17-2012, 02:29 PM   #2165
Pentaxian
jsherman999's Avatar

Join Date: Dec 2007
Photos: Gallery
Posts: 8,228
keeping FOV the same?

QuoteOriginally posted by Aristophanes Quote

We do look at photographs, right? The difference between f/5.6 on APS-C and f/8 on 35mm is hard to distinguish.

.
Did you really mean to say this? Because if we're talking about keeping FOV the same, then f/5.6 on aps-c and f/8 on FF should give you images tha look exactly the same with reagrds to DOF! (or within 1/3 stop.) So, yes, f/5.6 on aps-c and f/8 on FF is hard to distinguish, as described by equivalence.

f/5.6 on both aps-c and on FF would be easier to distinguish, the aps-c shot would have 1.3 stops more DOF. It's even easier to distinguish at the higher apertures at more distances to subject - f/2.8 on both formats, for example.

It really is the same rabbit hole that's been explored over & over & over again, I agree with that.



.
01-17-2012, 05:12 PM   #2166
Veteran Member
Pentaxor's Avatar

Join Date: May 2009
Location: Vancouver, B.C.
Photos: Gallery
Posts: 6,513
QuoteOriginally posted by jsherman999 Quote
Did you really mean to say this? Because if we're talking about keeping FOV the same, then f/5.6 on aps-c and f/8 on FF should give you images tha look exactly the same with reagrds to DOF! (or within 1/3 stop.) So, yes, f/5.6 on aps-c and f/8 on FF is hard to distinguish, as described by equivalence.

f/5.6 on both aps-c and on FF would be easier to distinguish, the aps-c shot would have 1.3 stops more DOF. It's even easier to distinguish at the higher apertures at more distances to subject - f/2.8 on both formats, for example.

It really is the same rabbit hole that's been explored over & over & over again, I agree with that.



.

I forgot to mention the scenario between DOF equivalence with regards to aperture speed. if such DOF adjustment is made, the APS-C loses some light as well by stopping down. again, compromises.
probably next time some people would argue how they can always increase the ISO. ahhmmmm, as mentioned, you just change the ISO which is a compromise.
01-17-2012, 05:42 PM   #2167
Pentaxian
Mareket's Avatar

Join Date: Jun 2011
Location: Chester
Photos: Gallery | Albums
Posts: 719
You need a full frame camera if you want one. If not, APS-C will never let you down. If you believe full frame cameras will make your pictures better then you're sadly mistaken.

Pentax haven't got a single model out that anyone REALLY wants, unlike the new Fuji or D4. Until they release a desirable camera then they're never going to do well. The Q was an excellent but half hearted attempt, and the K-5 masterfully conquers APS-C but it's not remotely exciting. The D3S had class leading speed, the D1X has the highest fps rates, the Fuji cameras have beautiful designs, and all have huge price tags. Pentax need to pick a niche to master and whack a huge price tag on whatever comes out. The Q mastered size, but wasn't elite or expensive enough.

Methinks
01-17-2012, 06:00 PM   #2168
Pentaxian
falconeye's Avatar

Join Date: Jan 2008
Location: Munich, Alps, Germany
Photos: Gallery
Posts: 6,862
QuoteOriginally posted by Pentaxor Quote
we try so hard on trying to equate two different systems.
No, we don't try hard to do so. It's a simple scale invariant, one of the most basic concepts physics is built upon.

And it just is the most basic level of understanding required to understand the impact of sensor format. Without it, any thinking must remain fuzzy. Trust me.


Last edited by falconeye; 01-17-2012 at 06:10 PM.
01-17-2012, 06:06 PM   #2169
Site Supporter
Aristophanes's Avatar

Join Date: Jul 2008
Location: Dartmouth, Nova Scotia
Photos: Albums
Posts: 3,790
QuoteOriginally posted by Pentaxor Quote
I forgot to mention the scenario between DOF equivalence with regards to aperture speed. if such DOF adjustment is made, the APS-C loses some light as well by stopping down. again, compromises.
probably next time some people would argue how they can always increase the ISO. ahhmmmm, as mentioned, you just change the ISO which is a compromise.
Why? If ISO 800 is now as clean a shot as ISO 400....?

Now you see how the marketing people think and why sensor ISO advances change all the rules.

The differences are most noticeable at the ends of the spectrum where the least shots are taken.; they are least noticeable where the bulk of market appeal lies, and where the ISO change obviates.
01-18-2012, 07:57 AM - 4 Likes   #2170
Veteran Member
fikkser's Avatar

Join Date: May 2010
Location: Borlänge, Sweden
Posts: 373
Is any of your comparisons relevant? FF lenses should be used with FF cameras, putting them on aps-c is a compromise in every way.

How many of you have actually tested your glass on both APS-C and FF?

The EOS 5D gave my Takumars new life. I can now use them as they are ment to be used, putting them on aps-c again is not going to happen. After using 5d the k-5 viewfinder feels like a long thin tunnel - it sucks!

If you like me want sharpness and short DOF you "need" FF. If you want shortest possible DOF with a 50 1,4 or whatever lens on APS-C you'll use it in 1,4 and it won't be sharp enough. On FF you can stop down, match the DOF of APS-C and get better sharpness. It would be crazy to make expensive fast glass for aps-c when you can make a more expensive FF body with cheaper glass that will perform the same or better.

I use my AF-lenses on k-5 and put my takumars etc. on the 5d. Great combo, but a Pentax FF - mirrorless or dslr would be perfect.
01-18-2012, 11:11 AM   #2171
Site Supporter
markku55's Avatar

Join Date: Dec 2011
Location: Hanko, Finland
Posts: 195
QuoteOriginally posted by fikkser Quote
Is any of your comparisons relevant? FF lenses should be used with FF cameras, putting them on aps-c is a compromise in every way.

How many of you have actually tested your glass on both APS-C and FF?

The EOS 5D gave my Takumars new life. I can now use them as they are ment to be used, putting them on aps-c again is not going to happen. After using 5d the k-5 viewfinder feels like a long thin tunnel - it sucks!

If you like me want sharpness and short DOF you "need" FF. If you want shortest possible DOF with a 50 1,4 or whatever lens on APS-C you'll use it in 1,4 and it won't be sharp enough. On FF you can stop down, match the DOF of APS-C and get better sharpness. It would be crazy to make expensive fast glass for aps-c when you can make a more expensive FF body with cheaper glass that will perform the same or better.

I use my AF-lenses on k-5 and put my takumars etc. on the 5d. Great combo, but a Pentax FF - mirrorless or dslr would be perfect.
Wonderfull, I like this, +1
01-18-2012, 12:48 PM   #2172
Site Supporter
Aristophanes's Avatar

Join Date: Jul 2008
Location: Dartmouth, Nova Scotia
Photos: Albums
Posts: 3,790
Luminous landscape

QuoteOriginally posted by fikkser Quote
It would be crazy to make expensive fast glass for aps-c when you can make a more expensive FF body with cheaper glass that will perform the same or better.
Cheaper glass?

And exactly how much cheaper is the Canon or Nikon FF glass right now?

QuoteOriginally posted by fikkser Quote
If you like me want sharpness and short DOF you "need" FF.
This is *exactly* why FF glass for all the brands (Sony-Zeiss, Canon, and Nikon) are so pricey.

That's the premium product, not the cheap one.

It was in the 1970's and 80's as well, when all those 50/1.2's and 1.4's came out for that "soft focus" look.
01-18-2012, 01:31 PM - 1 Like   #2173
Pentaxian
maxfield_photo's Avatar

Join Date: Mar 2011
Location: Cincinnati, OH
Posts: 1,216
Equivalency arguments are so entertaining, there are so many ways to think about it, and it's clear that everyone understands the principal, yet if you don't state it in the terms in which the other person thinks about it, you're wrong. Gotta remember to say things like "for a given subject", or "at a given distance". or "for a given print size". Where's my popcorn?
01-18-2012, 02:04 PM   #2174
Pentaxian
Asahiflex's Avatar

Join Date: Jan 2008
Location: Netherlands
Photos: Gallery
Posts: 2,753
I'll keep my mouth shut until the CP+ show in Japan, early february. I guess everything has already been said and done; now let's just sit back, relax and wait.
01-18-2012, 02:36 PM   #2175
Site Supporter
Zygonyx's Avatar

Join Date: Jun 2011
Location: Ile de France
Posts: 2,951
Yes, and let's hope Ricoh will bring more than pop corn to this show.
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!
aps-c, bodies, body, dslr, full-frame, lenses, lineup, pentax, system, users
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Full frame pentax cem.kumuk Pentax DSLR Discussion 11 11-12-2010 03:13 PM
Pentax and Full Frame... Shutter-bug Photographic Technique 60 11-03-2010 10:03 AM
Pentax A 50/1.2 on Full Frame aegisphan Pentax SLR Lens Discussion 23 10-28-2010 04:16 PM
News Regarding Advertising on PentaxForums.com: An Official Statement Adam Site Suggestions and Help 5 03-24-2010 07:37 PM
Official: New DSLR Body is Coming; Full Frame Model is Under Planning! RiceHigh Pentax News and Rumors 78 08-04-2008 06:18 PM



All times are GMT -7. The time now is 11:58 AM. | 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