Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
12-01-2011, 05:27 PM   #1546
Pentaxian
Mareket's Avatar

Join Date: Jun 2011
Location: Chester
Photos: Gallery | Albums
Posts: 719
But an ISO 800 f/4 1/100 image on any camera will have the same sort of exposure surely? Colour me confused. My film cameras agree with my K-5 when set at the same f stop and ISO. How would changing the size of the sensor alter the exposure? I'm not fussed about diffraction of depth of field, just exposure. I understand that a larger sensor will have lower noise at higher ISO settings, but is it really a full stop better?

So if I had a full frame camera, I'd get the exact same picture shooting at 1/100, f/2, ISO 800 than 1/100, f/1.4 ISO 400? Couldn't this be resolved with even better sensors on Pentax's behalf though? It's just an ISO issue, and APS-C sensors are getting better all the time.

Also, there are plenty of APS-C lenses you couldn't get the equivalent of on FF, such as a 120f/1.4 with Canon's 85mm f/1.2 on a 7D or whatever. I'm still confused by the ISO scaling thing. It's not a physical issue, so theoretically if APS-C sensors get better and better they'll get over that.

12-01-2011, 06:42 PM   #1547
Veteran Member
RXrenesis8's Avatar

Join Date: Jan 2011
Location: Orlando, FL (USA)
Photos: Gallery | Albums
Posts: 523
It actually IS a physical thing (if you are a "light is a particle" type of dude).

The simple explanation is: Because more light is hitting the sensor.
12-01-2011, 07:04 PM - 1 Like   #1548
Pentaxian
Class A's Avatar

Join Date: Aug 2008
Location: Wellington, New Zealand
Posts: 9,193
QuoteOriginally posted by benjikan Quote
Pentax already have their Full Frame camera. It is called the Pentax 645D.
Assuming the K-5 weren't weather-sealed, your statement is like saying "Pentax already have their weather-sealed camera. It is called the Pentax Optio W80".

Using "FF" only makes sense in the context of talking about crop sensors, i.e., when referring to sensors that do not crop the original image format of their mount.
(In that sense, the Pentax 645D is a crop camera as well, as it is not a full MF camera.)

The point is that W80, K-5/K-1(FF), and 645D are all different systems and from a typical photographer's perspective nothing would change if the two they didn't use disappeared or where offered by a different company. You could just as well say "Pentax shooters already have access to a full frame camera. It is called the Sony A900" (I believe referring to "Pentax shooters" rather than "Pentax" makes more sense in the forum's context because we are Pentax shooters, not running Pentax). The mounts used for the K-5 and the 645D are, to all intents and purposes, as incompatible as the K-5 mount is to the A900 mount.

QuoteOriginally posted by benjikan Quote
The FF market is very small compared to the rest, thus no reason for Pentax to go after the 35mm FF market.
That could have been said about the iPad market as well. There were numerous failed attempts at iPad and iPhone like attempts (even from Apple) that failed. If a Pentax FF camera is done right, it could become a huge success. A better success than a "K-5 super" (even if it has a different name) that no one feels compelled to buy because their K-5 is practically just as good (and produces smaller files).
12-01-2011, 07:20 PM   #1549
Site Supporter




Join Date: Mar 2009
Location: Gladys, Virginia
Photos: Gallery
Posts: 16,247
QuoteOriginally posted by Mareket Quote
But an ISO 800 f/4 1/100 image on any camera will have the same sort of exposure surely? Colour me confused. My film cameras agree with my K-5 when set at the same f stop and ISO. How would changing the size of the sensor alter the exposure? I'm not fussed about diffraction of depth of field, just exposure. I understand that a larger sensor will have lower noise at higher ISO settings, but is it really a full stop better?

So if I had a full frame camera, I'd get the exact same picture shooting at 1/100, f/2, ISO 800 than 1/100, f/1.4 ISO 400? Couldn't this be resolved with even better sensors on Pentax's behalf though? It's just an ISO issue, and APS-C sensors are getting better all the time.

Also, there are plenty of APS-C lenses you couldn't get the equivalent of on FF, such as a 120f/1.4 with Canon's 85mm f/1.2 on a 7D or whatever. I'm still confused by the ISO scaling thing. It's not a physical issue, so theoretically if APS-C sensors get better and better they'll get over that.
You are right. Basically, when it comes to equivalence, the question is really whether or not you want the depth of field to remain constant. You can view it as a negative or positive. I don't necessarily view it as a bad thing that my APS-C camera gives me an extra stop of depth of field compared to a full frame camera when shooting with the same settings otherwise, but some people really want more narrow depth of field. To me it isn't a big deal. Make Pentax cameras focus faster and more precisely, improve the speed of the lens line up, bring out better flashes and I could care less if that flagship camera is APS-C or full frame, but for those who want narrow depth of field and wide angles, full frame is the only way to go.

12-01-2011, 07:25 PM   #1550
Pentaxian
Class A's Avatar

Join Date: Aug 2008
Location: Wellington, New Zealand
Posts: 9,193
QuoteOriginally posted by Mareket Quote
But an ISO 800 f/4 1/100 image on any camera will have the same sort of exposure surely?
Yes, but that's because exposure is defined in terms of cd/m^2, i.e., light intensity per a unit area. If you keep the exposure constant, the camera with the larger sensor will collect more total light (same light per unit area but there are more unit areas). The increase in total light helps to bring down the noise (the signal to noise ratio, actually).

QuoteOriginally posted by Mareket Quote
I understand that a larger sensor will have lower noise at higher ISO settings, but is it really a full stop better?
That depends on how much larger the sensor is. If you are talking about the difference between APS-C and FF, yes, that's roughly a stop.

QuoteOriginally posted by Mareket Quote
It's just an ISO issue, and APS-C sensors are getting better all the time.
There is a limit to how good (noise free) a sensor can get and the K-5's Sony sensor is already pretty close. You cannot expect spades and spades of improvements in terms of reducing sensor noise anymore.

The remaining strategy to reduce noise is to use larger sensors and the correspondingly fast glass. Just using a large sensor doesn't help an iota with noise reduction. You also have to use a fast lens (which you have better chances of finding as FF lens, but not as an APS-C lens).

QuoteOriginally posted by Mareket Quote
Also, there are plenty of APS-C lenses you couldn't get the equivalent of on FF, such as a 120f/1.4 with Canon's 85mm f/1.2 on a 7D or whatever.
You can get the equivalent by just using the same lens (here the 85/1.2) on the FF camera. Provided that the FF sensor has sufficient resolution, you just crop the FF image to an APS-C sized one. A 24MP FF sensor can produce >10MP APS-C sized crops. That's more than sufficient for many applications.
12-01-2011, 07:44 PM   #1551
Veteran Member
jsherman999's Avatar

Join Date: Dec 2007
Photos: Gallery
Posts: 8,228
QuoteOriginally posted by Class A Quote
....
The point is that W80, K-5/K-1(FF), and 645D are all different systems and from a typical photographer's perspective nothing would change if the two they didn't use disappeared or where offered by a different company. You could just as well say "Pentax shooters already have access to a full frame camera. It is called the Sony A900" (I believe referring to "Pentax shooters" rather than "Pentax" makes more sense in the forum's context because we are Pentax shooters, not running Pentax). The mounts used for the K-5 and the 645D are, to all intents and purposes, as incompatible as the K-5 mount is to the A900 mount.
I like when folks say exactly what I was going to say, saving me all the composition and spell checking.

645D may be "the Pentax FF" as far as Hoya bean counters were concerned only; for most shooters it's a completely different genre of camera in performance to FF bodies (worse, in many attributes important to FF DSLR shooters,) and incompatible in mount to Pentax aps-c DSLR. Most Pentax aps-c DSLR owners would find a more apt 'upgrade' in the A900, D700, or 5dmII.

It's a great tool for specific uses - not as great when used as a general, do-everything DSLR.

QuoteQuote:
That could have been said about the iPad market as well. There were numerous failed attempts at iPad and iPhone like attempts (even from Apple) that failed. If a Pentax FF camera is done right, it could become a huge success. A better success than a "K-5 super" (even if it has a different name) that no one feels compelled to buy because their K-5 is practically just as good (and produces smaller files).
+2

.

Last edited by jsherman999; 12-01-2011 at 07:52 PM.
12-01-2011, 08:30 PM   #1552
Pentaxian




Join Date: Oct 2009
Location: North
Photos: Gallery
Posts: 3,921
QuoteOriginally posted by maxfield_photo Quote
Happy 100th page!! I didn't think we'd make it. 100 pages, 1486 posts, and 71,777 views and 136 "likes" in six weeks.
Ha...ha...
Kinda reminds me of that very popular "Show about Nothing"


12-01-2011, 09:22 PM   #1553
Loyal Site Supporter




Join Date: Apr 2010
Location: Tennessee
Posts: 5,801
QuoteOriginally posted by Mareket Quote
But an ISO 800 f/4 1/100 image on any camera will have the same sort of exposure surely? Colour me confused. My film cameras agree with my K-5 when set at the same f stop and ISO. How would changing the size of the sensor alter the exposure? I'm not fussed about diffraction of depth of field, just exposure. I understand that a larger sensor will have lower noise at higher ISO settings, but is it really a full stop better?

So if I had a full frame camera, I'd get the exact same picture shooting at 1/100, f/2, ISO 800 than 1/100, f/1.4 ISO 400? Couldn't this be resolved with even better sensors on Pentax's behalf though? It's just an ISO issue, and APS-C sensors are getting better all the time.

Also, there are plenty of APS-C lenses you couldn't get the equivalent of on FF, such as a 120f/1.4 with Canon's 85mm f/1.2 on a 7D or whatever. I'm still confused by the ISO scaling thing. It's not a physical issue, so theoretically if APS-C sensors get better and better they'll get over that.
You are correct in your assessment. Larger sensors will have larger photosites which produce a better signal to noise ratio. IF the edges of a 32MP FF sensor were masked off to the size of 16MP APS-C the center photosites do not become less efficient. They don't collect less light than they did before you masked off the edges. The same amount of light is still striking the center of the sensor.

What people see is that the image from an APS-C sensor has to be enlarged 50% more in order to equal the same output size from a FF sensor. And just like in the film days, the more you enlarge the image the more noise/grain becomes visible. Since most people look at noise at 1:1 the high pixel density of a 24MP APS-C image is going to look much noisier than a 1:1 crop of a 12MP image from a D3s. My math maybe wrong, but I believe a 1:1 crop of a 24MP APS-C is 4x the magnification of a 1:1 crop of a 12MP FF sensor.

Like with film you could use 400 ASA/ISO in a 6x7 and get much better results than 400 ISO in a 35mm. The film was the same, but because you are enlarging the 35mm 5x as much the images did not hold up and you needed to drop back down to 50 ISO to get comparable results.

12-02-2011, 12:15 AM   #1554
Veteran Member
maxfield_photo's Avatar

Join Date: Mar 2011
Location: Cincinnati, OH
Posts: 1,215
QuoteOriginally posted by Rondec Quote
but for those who want narrow depth of field and wide angles, full frame is the only way to go.
This is the real reason for me, lower noise is just a perk.

Consider this, if I go out shooting with my favorite APS-C portrait lens, the DA* 50-135, and I frame my subject the way I want, dial the aperture down to f/2.8 and snap my shot, I'm really getting f/4.5 worth of DoF, now that's not terrible, but it ain't like real 2.8 that I used to get on my film camera. Fortunately the 50-135 is very sharp even wide open, but many lenses aren't, some have to be stopped down to all the way to 5.6 to reach acceptable sharpness, that's like f/9 in 35mm terms.

Or if I break out my old 24mm f/2.8 for the family reunion photo at Thanksgiving I'm forced to make a decision: do I want to chop Uncle Phil off the left or Aunt Betty off the right of the image? If I could just back up farther it would be no problem, but there's a wall behind me, so I guess we're just going to have to go stand outside in the cold.
12-02-2011, 01:49 AM   #1555
Senior Member
Spag's Avatar

Join Date: Oct 2008
Location: Berlin
Photos: Gallery | Albums
Posts: 121
2012 will probably be a decisive year for the future of Pentax. Users are eager to see what is Ricoh going to do with it and what direction Pentax as a brand will go. At the same time Canon (and probably Nikon too) will bring new FF cameras on the market.

If there is no FF from Pentax in 2012 I guess I will swith to Canon, even if I love my K-5 and the Pentax ergonomics. But don't start to hate me yet: I will keep my old K1000 (film) and my 67.
12-02-2011, 01:52 AM   #1556
Senior Member
Kryscendo's Avatar

Join Date: Sep 2011
Posts: 223
See I don't get this. I'd rather have a massive lens library than starting over with a Canon or a Nikon. Still, 2012 will be an interesting year.
12-02-2011, 03:36 AM   #1557
Pentaxian
Mareket's Avatar

Join Date: Jun 2011
Location: Chester
Photos: Gallery | Albums
Posts: 719
But for the shot to be properly exposed each pixel needs to gather the right amount of charge from photons hitting it right? So making the sensor bigger doesn't make each pixel suddenly get more light, unless the size of each pixel is increased. So the exposure is still the same, as at f/2.8 1/100 ISO800 each pixel is receiving a certain amount of light, whether it's in APS-C or FF, so the total exposure is the same? The bigger sensor is getting more light yeah, but that doesn't mean each individual pixel gets more light unless they get bigger, so the overall exposure will be the same.

And yeah, APS-C sucks for wide angle, but you just have to buy the appropriate lens. And does the reduced DoF REALLY make the shots all that worse? Also bear in mind that FF will bring out the harsher vignetting/edge softness/CAs and all that of whatever lens you use. And surely if you're not viewing the images at massive sizes (like normal people) the benefits (aside from DoF) aren't easily seen anyway? You won't be able to tell the difference (generally) between a FF shot and an APS-C shot in pretty much any situation you'd use them in, unless you enlarged them for posters. But how often do people really do that?

So people are hoping they can pay thousands of pounds/dollars/whatever more so they can have reduced DoF and for their lenses to be wider? Why?
12-02-2011, 04:10 AM   #1558
Senior Member
Spag's Avatar

Join Date: Oct 2008
Location: Berlin
Photos: Gallery | Albums
Posts: 121
QuoteOriginally posted by Kryscendo Quote
See I don't get this. I'd rather have a massive lens library than starting over with a Canon or a Nikon. Still, 2012 will be an interesting year.
I like every single lens I have, but most are basically just sitting there... When I take my camera bag for a tour I choose up to 5 lenses max, and rarely one of these oldies, even if they are fun to play with.
12-02-2011, 04:31 AM   #1559
Senior Member




Join Date: Sep 2006
Posts: 259
QuoteOriginally posted by jeztastic Quote
As far as I can see we're all European, including the guy who posted it. I think it's a great photo, but not the kind of thing a boss would easily turn a blind eye to, anywhere in the world!
Your boss doenst like women?

It would be good if you do not be offended so easily. If you do not want see pictures in your screen, why you are browsing at all in the work? shouldnt you be working?
12-02-2011, 08:00 AM   #1560
Veteran Member
falconeye's Avatar

Join Date: Jan 2008
Location: Munich, Alps, Germany
Photos: Gallery
Posts: 6,863
QuoteOriginally posted by Mareket Quote
So making the sensor bigger doesn't make each pixel suddenly get more light, unless the size of each pixel is increased. So the exposure is still the same, as at f/2.8 1/100 ISO800 each pixel is receiving a certain amount of light, whether it's in APS-C or FF, so the total exposure is the same? The bigger sensor is getting more light yeah, but that doesn't mean each individual pixel gets more light unless they get bigger, so the overall exposure will be the same.
I'd like to see the day that people new to the topic ask the proper questions in order to understand this confusing topic. Rather than assuming their prior understanding must be correct.

In order to help you reason about the topic: Assume two sensors, both say 24MP, one APS-C and one FF. Then the two images will be called "equivalent" if two corresponding pixels have collected the same number of photons. However, in order to achieve this, the ISO number on the larger sensor will be twice as high.

As a side effect, a larger sensor's pixel will typically not be "full" if the smaller sensor's pixel is. This translates in higher dynamic range for larger sensors. Not all silicon implementations make full use of this though, due to cost reasons.

In case the two sensors have pixels of equal size, i.e., the larger sensor has more pixels, then the same argument still holds true: because you scale noise down by downsizing an image.

QuoteOriginally posted by Mareket Quote
Also bear in mind that FF will bring out the harsher vignetting/edge softness/CAs and all that of whatever lens you use.
The opposite is true. Another common misconception.

It is true that FF lenses have weaker corners and more vignetting/CA problems, relative to the center. But that doesn't matter, esp. as FF lenses have a much sharper center and are stopped down more in equivalent images. You must compare corners and CA etc. between an APS-C lens and an equivalent FF lens. And then the equivalent FF lens wins hands down. It's just not a comparison done by any test report. You have to look up the individual figures and do the comparison yourself.

As a start, compare the Canon 70-200/4 L vs. the Pentax 50-135/2.8, in absolute LW/PH figures ...
(both lenses cost about the same, weight the same and are equivalent. But the FF lens has twice the border resolution at full aperture ... So, what corner sharpness are you talking about?

QuoteOriginally posted by Mareket Quote
So people are hoping they can pay thousands of pounds/dollars/whatever more so they can have reduced DoF and for their lenses to be wider? Why?
I hope you understand the reasons are elsewhere.

It's not only a larger spectrum of lenses. Available lenses for FF should be cheaper (when equivalent) for physical reasons, or at a given price, they should be sharper. Beyond a given point in resolution, APS-C will become unaffordable (FT already passed this point with their crop-2 factor and APS-C will do soon too). And eventually, FF allows for more accurate AF operation for reasons I am too lazy to explain now.
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 01:12 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