Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
12-23-2010, 01:13 PM   #16
Senior Member




Join Date: Nov 2008
Location: Park City, Utah
Posts: 208
Original Poster
hmm seems to be very little consensus on this issue, Shooting at f16 on a 645D I wonder about diffraction or is this whole diffraction thing over rated in real world shooting and then going to print.

I was just assuming if I got "A" manual focus lenses that I can still use the AF system to help aid in focus and if need be do the fine tune thing so when the focus indicator is lit in the finder it actually is in focus, or is there even an issue with this approach??

12-23-2010, 03:54 PM   #17
Senior Member




Join Date: Nov 2010
Location: Beach Haven, NJ
Posts: 176
Kuau:
Please see my addendum to my post First Impressions by an amateur. You may find, that for your kind of work, as I have found, focusing and DOF at f13, f16 are not an issue. I don't make a living doing this, but do sell a lot of work. My clients will be pleased with the 645D results.
Dave
12-23-2010, 08:31 PM   #18
New Member




Join Date: Dec 2010
Location: Boulder, CO
Posts: 10
QuoteOriginally posted by kuau Quote
I was just assuming if I got "A" manual focus lenses that I can still use the AF system to help aid in focus and if need be do the fine tune thing so when the focus indicator is lit in the finder it actually is in focus, or is there even an issue with this approach??
My short set of experiments says that the focus-assist isn't good enough. My eye is better. But, if you do want to use it, you may observe that it will work slightly better in one zoom direction than the other.
12-26-2010, 06:35 AM - 1 Like   #19
Senior Member




Join Date: Oct 2010
Location: Toronto, Canada
Posts: 132
Pal,

I have shot with just about every MF system made since 1990 (except Rollei). I have also used almost all of the MF digital systems. The principles of DOF and diffraction are obviously the same with digital, but the practical results are not. There are several reasons for this, which have been thoroughly gone-over elsewhere, so I will not repeat here. Those who 'disbelieve' this have one having in common: not having shot with MF digital systems.

Yes, the 645D has vastly better resolution than most 35mm camera, and yes, it renders more sharply than a non-AA'd camera. Getting that difference to actually mean much in practice, on near-infinity subjects, is much trickier (and dependent on exacting calibration b/w lens and body) than most people know.

That's all I am saying.

As for manually focusing lenses accurately on the 645D, good luck to you all. My eyes are as good as most on here, and I cannot generally match the AF. The screens used in these cameras are nowhere near as acute as the last generation in the film bodies.

- N.

12-26-2010, 07:51 AM   #20
Senior Member




Join Date: Nov 2008
Location: Park City, Utah
Posts: 208
Original Poster
Nick since you have shot with the 645d I will take your advice and stick with FA lenses I am thinking the 45fa 75fa 150fa and 200fa
I use to shoot a H3D-39 so i am familiar shooting mfd my favorite lenses for me on the hassy was the 50 and 150 I also owned the 28 which was very nice but I am not a great wa shooter and I had the 80 which was sometimes a tad short for me which I had the 100, yet to expensive. I use to use there 1.7tc on my 150! A lot of the times

As of today I shoot with M9 and 4 lens

If and when i do receive my 645d from pentax and if it can't resolve fine detail way out close to infinity like my hassy could or m9 can no problem I'm sending it back to pentax for a refund and will sell my 3 fa lenses and lose just a little money.

Steven
12-27-2010, 12:49 PM   #21
Veteran Member




Join Date: Feb 2010
Location: Fowlmere, UK
Photos: Albums
Posts: 696
QuoteOriginally posted by ndevlin Quote
The screens used in these cameras are nowhere near as acute as the last generation in the film bodies.
That is an interesting observation. Not having held the 645D, I cannot compare, but could you elaborate on this? Is this a particular issue with the 645D or one with MF digital, or any digital, slr in general?

I have the K-x for convenience, and don't like the screen, but then again, the format is so much smaller that I ascribe issues with focussing to the APS-C sized sensor My eyes? No way!
12-27-2010, 02:47 PM - 2 Likes   #22
rlj
Junior Member




Join Date: Nov 2009
Posts: 29
Hyperfocal DOF

Hyperfocal focusing with digital works just fine, but there is a significant difference between what we used to do with medium film and the digital sensors. The first issue is one of circle of confusion (COC) is different so using any markings for DOF from lenses designed for film will not work.

I'll give a crude example of what works on my Alpa and Phase 65+, and is applicable to any other camera. With the Apla set up, I always shoot with a Rodenstock HR-Digaron 35mm or 60mm lens using hyperfocal focusing. But to make it accurate, I first had to test each lens at a specific f-stop.

Testing was done by shooting images while gradually moving the focusing helicoid, moving the infinity mark from infinity to various landmarks on the lens. I repeated this for f8 and f11 (the only f-stops I use with this set up).

I found that when examining the files at 100%, focus at infinity was maintained when the right edge of the infinity mark was on the f-stop 1 f-stop less than shooting aperture. So for a lens at f11, and I put the edge of infinity mark at f8 and all is good. The point is that this test must be done for each of your lenses you wish to use for manual, hyperfocal focusing and is specific for the particular sensor.

However, there is a 'but' to the above, which leads to 2nd issue that we didn't experience with film because the film was not so flat and our standards for sharpness not as demanding as today when we view images at 100% pixel size.

The 2nd issue is how accurately the lens and body are adjusted for the particular sensor. This is where the Alpa system is flexible: shimming the back. I've had a few loaner Phase backs for various reasons and each one is different with respect to shimming requirements. (Which begs the question, how accurate are any digital cameras due to tolerances in manufacturing/assembly.)

The shimming is done by focusing on a very distance object (over 5 miles for 100mm lens) with the lens set at infinity and the f-stop wide open. Sequential images are made, while adjusting the spacers which can move the sensor forwards or backwards in 0.01mm (or larger) increments. Doing this gives very sharp images, and then lets the hyperfocal system work well.

The problem with virtually all other cameras is that we cannot shim them ourselves as one can with Alpa. We are at the mercy of the accuracy of the manufacturer. Pentax, with the micro-focus adjustment feature, does allow us to somewhat compensate for the sensor variation with AF lenses. But this actually only works with near targets (which is fine for many subjects).

The problem is if a particular lens/camera is 'over-shimmed'. If 'over-shimmed', the camera cannot be focused at infinity, and no amount of fiddling with software will help. If the particular lens/camera is not too far off, with respect to being 'over-shimmed', then stopping the lens down may allow infinity focus via hyperfocal focusing.

It is in this latter situation, where hyperfocal focusing gets a bad name in the digital realm, since one is 'chewing' up the hyperfocal distance just to get infinity objects into focus, let alone closer objects.
12-27-2010, 03:01 PM   #23
Senior Member




Join Date: Nov 2010
Location: Beach Haven, NJ
Posts: 176
rlj: Thanks for the excellent explanation.
Dave

12-28-2010, 03:45 PM   #24
Senior Member




Join Date: Oct 2010
Location: Toronto, Canada
Posts: 132
RLJ:

A terrific explanation of a complex issue. Everyone I know with an Alpa has had the same experience: when properly shimmed, the performance is astonishing, and markedly better than traditional lens/camera combos with the identical back.

The problem is most acute if a particular lens and camera are 'out' in opposite directions.As you say, infinity focus may then become impossible. I will be very interested in how my system performs when it comes back from Japan. I wonder if they will adjust the camera and/or lenses to match one another, if they can.

- N.
12-28-2010, 04:33 PM   #25
Senior Member




Join Date: Nov 2008
Location: Park City, Utah
Posts: 208
Original Poster
I was just checking out
Pentax 645D в усадьбе "Архангельское" - managger - Участники - Фотогалерея iXBT

Wow, I was looking at the sample from the 35mm FA, I thought it looked terrible, and it was shot at F22, sure some diffraction but it had bad ca in the corners and the image was not sharp at all.
I thought the 120mm looked good, the 200mm looked good even the 45mm looked good. But the 35mm looked yuk...
12-28-2010, 06:31 PM   #26
Forum Member
leping's Avatar

Join Date: Sep 2010
Location: Chicago, IL, USA
Posts: 82
QuoteOriginally posted by kuau Quote
I was just checking out
Pentax 645D в усадьбе "Архангельское" - managger - Участники - Фотогалерея iXBT

Wow, I was looking at the sample from the 35mm FA, I thought it looked terrible, and it was shot at F22, sure some diffraction but it had bad ca in the corners and the image was not sharp at all.
I thought the 120mm looked good, the 200mm looked good even the 45mm looked good. But the 35mm looked yuk...
Actually this is better than what I thought. Of course at f/22 nothing is really sharp, but as with all the 645D images it withstands a lot of sharpening even multiple pass (with decreasing radius) and you can correct for CA, to some extent, in RAW conversion. No one's MF wide angle lenses are really sharp to the corners. Not even the Canons on 35mm and Nikons until the 14-24 came up. 47mm XL, 58mm XL, and 65/75mm on LF film, used to be the only games in the town if you really want quality wide angle shots technically.

Remember as a matter of fact, the Pentax FA 35mm beats the Hasselblad and the Mamiya in this review:

Pentax 645 FA 35mm Review

Had you looked Ansel or his F64 school buddy's 8x10 negatives (shot at f/45, and f/64 and beyond) though a loupe? Or Michael Fatali's big prints in which details are not really sharp? Even this image makes great 24x30 after some clinical work -- just forget 100% view into the pixels.

Little soft lenses coupled with high resolution sensors reduces "digital flavor", demosiacing artifacts, and moire.

The 35mm sample on this page has better sharpness but improperly sharpen and look too digital to my taste:

http://translate.google.com/translate?u=http%3A%2F%2Fganref.jp%2Fmagazines%2...n&hl=&ie=UTF-8
Attached Images
 

Last edited by leping; 12-29-2010 at 12:37 AM. Reason: 1
01-02-2011, 11:44 PM   #27
Veteran Member




Join Date: Jun 2010
Location: Marina CA
Posts: 300
Is everybody really saying that nobody ever got properly focused pictures before autofocus ? Also, yes, depth of field is an illusion. It is an illusion that has worked ever since the beginning of photography. In some ways, pixel peeping doesn't show what people are going to see when viewing the photo. Has anyone stood really close to an Ansel Adams photo blown up to 30x40 or bigger? They look marvelous at normal viewing distances.
01-03-2011, 07:08 AM   #28
Senior Member




Join Date: Jun 2010
Location: Hamburg
Posts: 267
QuoteOriginally posted by ARCASIA Quote
Hi Steven,

I would suggest that before anyone categorically rules out MF lenses, they tryout on the 645D a Pentax 67 55/4, 75/4.5, 100/4 macro, or a 300/4 M*, and maybe a CZJ 50/4 Flektogon or a 180/2.8 Sonnar. I suspect that you will be very pleasantly surprised at the results, and your pocketbook will also be very happy!

Best, Alan
Hi Alan,

I own these 67 lenses and I love them on my 67II! I am esp. fond of the 100mm macro - what a great lens.
I am thinking about getting the 645D. There's an adapter available for the use of the 67 lense range on the older 645 system. Does this work with the 645D, too? And will I have full aperture control? Means when I set the 100mm Macro at 4.0 or 8 or 11, will it show in the display of the 645D?
Thanks for an answer!
Alex

Last edited by phonoline; 01-03-2011 at 08:27 AM.
01-03-2011, 08:52 AM   #29
Senior Member




Join Date: Nov 2010
Location: Calgary, Alberta
Posts: 265
Alex -- the Pentax 67-to-645 adapter does work on the 645D. A number of people are using it, including Chris Willson (Travel 67). I picked up the adapter recently to try my hand with some 67 lenses, the first of which I just received -- the 105mm f/2.4.

The lens aperture setting does not show in the 645D display (and is not encoded into the image EXIF data). But the camera does meter correctly and uses the lens auto-diaphragm so you don't have to shoot in manual stop-down fashion.
01-03-2011, 09:03 AM   #30
Senior Member




Join Date: Jun 2010
Location: Hamburg
Posts: 267
Royce, that means when I set the lens at 2.4 (in case of the 105mm), the metering system of the 645d recognizes this, doesn't show it onscreen and in the EXIF but meters shutter speed correctly, right?
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!
camera, fa, lens, medium format
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Bold headshot statement RonHendriks1966 Video and Pentax HDSLRs 1 12-01-2010 06:58 PM
News Regarding Advertising on PentaxForums.com: An Official Statement Adam Site Suggestions and Help 5 03-24-2010 07:37 PM
is there such a thing as a m42 true macro lens ? janstew Pentax SLR Lens Discussion 7 02-20-2010 04:54 AM
Intresting statement from a stranger... lodi781 General Talk 19 02-28-2009 10:09 AM
Pentax has no any inspection system at lens plants in Vietnam. Is it true? ogl Pentax News and Rumors 19 05-14-2008 07:30 AM



All times are GMT -7. The time now is 01:36 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