Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
02-05-2012, 10:53 AM - 1 Like   #31
Veteran Member




Join Date: Mar 2011
Location: Arizona
Photos: Albums
Posts: 330
QuoteOriginally posted by Ed Hurst Quote
Focus stacking? :-)
I wish for a focus stacking mode in the 645DII. The camera should automatically bracket the focus just like exposure bracketing mode. Then let you combine the images yourself. A mode for one touch focus bracketing. This way I don't have to touch the camera and risk a slight movement to composition... I see no reason why this can't be implemented for using FA or DFA lenses.

BTW, I think this discussion is crazzy. Sometimes I get better images from my K5 and compact limited primes. These are images I can't get with a 645N or D because it is 20miles off the road and 5,000ft of elevation gain. Sometimes I get better pictures with the 645N and manual focus lenses because it makes me concentrate more. Sometimes I get better pictures with auto focus 645 lenses because that second saved captures the moment. Sometimes I got better pictures with the K mount FA* 300mm 2.8 because there is just no substitute for that lens with the 645 system... When I get my 645D I think sometimes it will give me better pictures because I will have the option to check the image in camera. Allowing me to fix it asap, not waiting 2 or 3 days to find out that I was off or that slight breeze blurred the grass and hoping for the exact same light, cloud formation, etc. when I return...

Cost of the camera isn't the final decision for choosing a system. I can buy a 1970's dump truck cheaper than a brand new toyota corolla. Does that at all mean the dump truck has a cheaper operating cost? Does that at all mean the corolla will haul as much as the dump truck. Does that at all mean the dump truck will navigate city streets as easily? You use what you need to to get the image.

02-05-2012, 11:11 AM   #32
Pentaxian




Join Date: May 2011
Location: All over the place
Posts: 2,596
Agree 1000%
02-06-2012, 10:55 AM   #33
Forum Member
chicagonature's Avatar

Join Date: Jan 2011
Location: Downers Grove, IL
Posts: 89
In keeping with the 645D vs. 645N (film) question, I wonder how the effects of diffraction affects the final images.

What I'm asking is, do digital sensors become "diffraction limited" at a different aperture than film (all other things being equal and assuming a very high quality lens)? If so, which factors matter and how do they matter: anti-aliasing filter, size of pixels, pixel density, microlenses to better capture the light?

I'm hoping we have some scientists on this forum!

Thanks!
02-06-2012, 03:56 PM   #34
Veteran Member




Join Date: Feb 2011
Photos: Gallery
Posts: 573
The terms are optics limited and sensor limited. Basically, it comes down to format size. So while you might see diffraction at 100% viewing, it is more important to consider diffraction at a condition you would actually view an image. Naturally, the effect of diffraction can be personal but that will be relative across formats. The difference between the film and digital 645 is proportional to the crop factor--1.36. So the diffraction tolerance changes by about one stop (1.4 is the square root of 2)--if you think the limit is f/22 on the film frame, it will be f/16 on the digital sensor.

02-06-2012, 05:58 PM   #35
Forum Member
chicagonature's Avatar

Join Date: Jan 2011
Location: Downers Grove, IL
Posts: 89
QuoteOriginally posted by Yamanobori Quote
The terms are optics limited and sensor limited. Basically, it comes down to format size. So while you might see diffraction at 100% viewing, it is more important to consider diffraction at a condition you would actually view an image. Naturally, the effect of diffraction can be personal but that will be relative across formats. The difference between the film and digital 645 is proportional to the crop factor--1.36. So the diffraction tolerance changes by about one stop (1.4 is the square root of 2)--if you think the limit is f/22 on the film frame, it will be f/16 on the digital sensor.
But, I was saying "all things being equal" and that includes the format. Given that, are you saying that diffraction affects image quality the same no matter if its digital or film?
02-06-2012, 06:03 PM   #36
Veteran Member




Join Date: Feb 2011
Photos: Gallery
Posts: 573
The short answer is yes. The more complicated one is maybe.
02-06-2012, 10:29 PM   #37
Forum Member
chicagonature's Avatar

Join Date: Jan 2011
Location: Downers Grove, IL
Posts: 89
QuoteOriginally posted by Yamanobori Quote
The short answer is yes. The more complicated one is maybe.
What role does an anti-aliasing filter play? The 645D does not have one.
02-08-2012, 03:32 AM   #38
Pentaxian
Digitalis's Avatar

Join Date: Mar 2009
Location: Adelaide.
Posts: 8,877
QuoteOriginally posted by stevebrot Quote
This is so true. With medium and large format, small apertures are a fact of life if you need deep DOF. This is true even for cameras with movements if you are at all close to the subject. Steve
I concur, with 8X10 format my Rodenstock 240mm f/5.6 APO Sironar performs optimally at f/22 - but often I find stopping down to at f/45~64 is necessary for landscapes especially with camera movements used for near/far compositions. Photographers with fixed focal planes and smaller sensors count your blessings!

QuoteOriginally posted by chicagonature Quote
What I'm asking is, do digital sensors become "diffraction limited" at a different aperture than film (all other things being equal and assuming a very high quality lens)? If so, which factors matter and how do they matter: anti-aliasing filter, size of pixels, pixel density, microlenses to better capture the light?
It would have to be one hell of a lens but even the greatest lenses ever made succumb to diffraction. And no, digital sensors are not diffraction limited**. For digital sensors there is the nyquist limit* - the amount of resolution a sensor can sample. Microlenses only increase the amount of photons a single pixel will receive - they have no real impact on resolution as such. The AA filter attenuates signals that approach or exceed the nyquist limit to prevent aliasing the AA filter applies this to all frequencies of light equally. Diffraction is also dependant on the frequency of light, with higher frequency light (E.g :ultra violet,violet,blue)being affected less than longer ones(yellow orange,Red, Infared).

*defined as being one half of the sampling frequency (in this instance #pixels/mm)

**One of the reasons why diffraction wasn't considered a huge problem with film is because there were often bigger problems reducing the chances of achieving maximum resolution e.g photographic technique, film flatness, correct alignment of the ground glass relative to the film plane, focus accuracy - just to name a few. The only situations where diffraction has always been an issue is macro photography - if you stop down too much you will lose image quality - if you don't stop down far enough the subject mightn't be recognisable.


Last edited by Digitalis; 02-08-2012 at 03:57 AM.
02-08-2012, 02:16 PM   #39
Senior Member
Paul MaudDib's Avatar

Join Date: Jul 2009
Location: Michigan
Posts: 292
QuoteOriginally posted by chicagonature Quote
In keeping with the 645D vs. 645N (film) question, I wonder how the effects of diffraction affects the final images.

What I'm asking is, do digital sensors become "diffraction limited" at a different aperture than film (all other things being equal and assuming a very high quality lens)? If so, which factors matter and how do they matter: anti-aliasing filter, size of pixels, pixel density, microlenses to better capture the light?

I'm hoping we have some scientists on this forum!

Thanks!
What matters re: diffraction is the size of the Airy disc. Think of a lens wide open: the rays of light are coming straight into the film. Now imagine you're stopped down, so to cover the image the rays have to come at an angle. Say you're taking a picture of a series of pinpoints of light. Since light is a wave, the rays add and cancel in a pattern, so each pinpoint of light actually looks like a bullseye. This is called an Airy disc. As you stop down more, the rays get more angular and the Airy discs get bigger. If they start to cross each other, then you're losing some information due to diffraction.

I'm probably getting this wrong, so here's a link. Diffraction Limited Photography: Pixel Size, Aperture and Airy Disks

The uptake of this is that the smaller the format, the denser the sensors have to be for a given resolution, so the quicker the Airy disc exceeds the diffraction limit. Conversely though, you have to stop down more with a larger sensor to achieve the same depth of field. You can think of it as distributing your resolution differently: small sensors give less resolution over a wider depth of field, large sensors give more resolution over a narrower depth of field. Of course, in the real world there aren't discrete sensor sites in film, it's all silver halide, and the larger format also makes up for the loss of resolution somewhat.

AA filters trade some resolution for a reduction in moire, which is another addition/cancellation phenomenon.
02-08-2012, 02:31 PM   #40
Senior Member
Paul MaudDib's Avatar

Join Date: Jul 2009
Location: Michigan
Posts: 292
My personal take on the MF film vs digital is this: digital is the obvious choice for a professional. There is simply no comparison in terms of cost, you would blow a huge fraction of your budget to shoot a wedding on film nowadays, let alone all the time to scan or the insane cost of paying someone to scan for you. You save thousands per year, which makes it a no-brainer.

For the rest of us, I think medium format is just fine. You are losing a lot of resolution by using the consumer grade equipment most hobbyists can afford, but medium format helps counteract that with sheer negative size, and you retain the option of wet prints to get more detail later. It's not as expensive as large format, and MF scanners are much cheaper than LF scanners. I'd really love to see a comparison using wet prints, as I feel that's the gold standard for film. I have lifted the head on my enlarger all the way up and printed a crop from 35mm as large as I can, and there's still lots of detail there. I don't feel I would get that from my (cheap flatbed) scanner. I've never gotten drum scans, but I still kind of doubt that they can extract more information than a wet print. Also, the negative will handle highlights a lot better than the DSLR, I tend to agree there is the potential for more dynamic range there.

Maybe a top of the line DSLR with great glass will give a better image file than a $500 medium format setup. Maybe not. I can tell you which I can afford, though.
02-08-2012, 03:52 PM   #41
Veteran Member




Join Date: Feb 2011
Photos: Gallery
Posts: 573
QuoteOriginally posted by chicagonature Quote
What role does an anti-aliasing filter play? The 645D does not have one.
In diffraction? Not much. These are two different things. The AA filter slightly blurs the image to eliminate moire and works at every aperture. The lack of an AA filter gives better/different micro contrast.

You also need to think in terms of the final print and the viewing distance. To say at 100% you can see diffraction is not very meaningful--if I have a small chip or a large chip, the appearance of the image will look different even though it is effecting the pixels equally simply because you are going through different scaling. This is why diffraction is based on format size, not pixel pitch. This is also why pixel peeping is a bad why to determine the effects of diffraction--ultimately we want the final image, print or web image, to look good.

BTW, diffraction is just as much an issue in film as it is digital. It is just we don't often view the results the same way--I only ever had a 10x loupe, which is far less magnification than when I view a 645D file at 100%. I had no problem seeing diffraction in film and determining sharpness with a loupe.

Last edited by Yamanobori; 02-08-2012 at 05:34 PM.
02-08-2012, 10:39 PM   #42
Site Supporter
Site Supporter
stevebrot's Avatar

Join Date: Mar 2007
Location: Vancouver (USA)
Photos: Gallery | Albums
Posts: 27,663
QuoteOriginally posted by Paul MaudDib Quote
you would blow a huge fraction of your budget to shoot a wedding on film nowadays, let alone all the time to scan or the insane cost of paying someone to scan for you. You save thousands per year, which makes it a no-brainer.
...unless, of course, your client insists on film. There is a high-end boutique market for film-based wedding photography here in the Portland area. But wait! There is more! Would you believe B&W?


Steve
02-09-2012, 05:44 PM   #43
Pentaxian
Digitalis's Avatar

Join Date: Mar 2009
Location: Adelaide.
Posts: 8,877
QuoteOriginally posted by stevebrot Quote
.unless, of course, your client insists on film. There is a high-end boutique market for film-based wedding photography here in the Portland area. But wait! There is more! Would you believe B&W?
And if you know how to make platinum prints you could milk the use of B&W film it for all it is worth, who wants a silver gelatin print these days? producing one 8"X10" platinum print typically sets me back about $150 in time and materials so upscale the print size to 16"X20" and the cost works out to closer to $900.

I'm amazed wedding photographer lensmonkeys have never figured that one out, I have heard of wedding photographers getting their prints done at Big-W and places like that....perhaps because platinum printing involves a big investment in time and a substantial amount of skill.

/rant - sorry I couldn't help myself I know wedding photographers who are just in it for the money, and personally that is abhorrent to me.
02-10-2012, 12:32 PM   #44
Pentaxian




Join Date: Jul 2009
Location: Seattle
Posts: 7,139
QuoteOriginally posted by stevebrot Quote
This is so true. With medium and large format, small apertures are a fact of life if you need deep DOF. This is true even for cameras with movements if you are at all close to the subject.

Steve
With wet printing. With the figital work flow and film, you can focus stack too if you wanted.
02-10-2012, 12:42 PM   #45
Loyal Site Supporter
Loyal Site Supporter
eddie1960's Avatar

Join Date: Aug 2010
Location: Toronto
Photos: Gallery | Albums
Posts: 12,273
QuoteOriginally posted by jogiba Quote
Not


Re: PENTAX 645D Why so expensive?: Pentax SLR Talk Forum: Digital Photography Review

Poor guy needs to see the light. I still have my 67 Pentax with four lenses and a Beseler 16CP table top processor for Cibachrome/Ilfochrome , Beseler 45MXT enlarger w/ Minolta 45 head and top of the line lenses along with Epson V700 Photo scanner but have not used the setup in a long time. I admit if you like the workflow the MF film setup is the best bang for the buck today but forget about comparing it to the 645D. Here is an old shootout of the old 2002 11mp Canon 1Ds vs the 67 Pentax :

Shootout

2002 11mp Canon 1Ds :


Pentax 67 :
HMMMM that building looks very familiar
The Royal York I presume
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!
645d, camera, canon, film, format, image, lenses, medium, medium format, pentax, shootout
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Pentax SMCP-FA 645N 80-160mm f/4.5 lens on Pentax 645D Imatest results JDOAK Pentax Medium Format 6 01-23-2011 12:56 PM
645D vs 645N comparison Thomas Pentax Medium Format 21 12-31-2010 05:20 PM
Panasonic GH2 beats the Canon 5D MKII jogiba Non-Pentax Cameras: Canon, Nikon, etc. 17 12-27-2010 06:40 AM
Shutter sound of 645D and 645n II igorphoto Pentax Medium Format 1 11-01-2010 06:31 AM
67 y.o. man beats up black kid on bus! Gooshin General Talk 58 03-07-2010 12:24 PM



All times are GMT -7. The time now is 11:38 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