Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
08-26-2009, 01:18 PM   #1
Veteran Member
MJB DIGITAL's Avatar

Join Date: Jul 2007
Location: st. louis
Posts: 1,173
Shot in the foot? Speed of Larger Format revisited

Well I learned in the last thread that the time of exposure isnt changed by the size of the format.

But I do know that the DOF is thinner.

So if you were shooting a bit longer of a focal length--in available light--and you needed to open up your lens to a wider aperture, you might have too thin of DOF....

is that right?

08-26-2009, 01:35 PM   #2
Veteran Member
Gooshin's Avatar

Join Date: Sep 2007
Location: Toronto, the one in Canada.
Posts: 5,611
as compared to a 35mm or an APS-C counterpart, yes.

edti:

which is where the Olympus top of the line zooms shine for certain work. They have two F2.0 zooms that cover the conventional 24-200mm (in 35mm terms) range, with twice the depth of field.

so you shoot wide open, but lots of stuff is in focus!
08-26-2009, 08:52 PM   #3
Veteran Member
Venturi's Avatar

Join Date: Mar 2008
Location: Tulsa, OK
Photos: Gallery
Posts: 2,639
QuoteOriginally posted by MJB DIGITAL Quote
Well I learned in the last thread that the time of exposure isnt changed by the size of the format.

But I do know that the DOF is thinner.

So if you were shooting a bit longer of a focal length--in available light--and you needed to open up your lens to a wider aperture, you might have too thin of DOF....

is that right?
"It is right" depends on what assumptions you are making when drawing the comparison.

If you stand 10ft from the subject with a 50mm lens and aperture at f/8:
- APS-C gives you a DOF of 39" and FOV of 68"
- 135 (full-frame) gives you a DOF of 62" and FOV of 104"

However and this is where the "DOF is thinner with full-frame" argument lies...

If you use a 50mm lens and aperture of f/8 and frame your shot so you have a 6ft (72") FOV:
- With APS-C you'll be standing 129in (10ft9in) from subject and have a DOF of 45.5".
- With 135 you'll be standing 7ft (84in) from subject and have a DOF of 29.5". To remain at 10.75ft from subject you'd need a 77mm lens to achieve the same FOV at f/8 and your DOF would drop to 28.8".

The argument is not wrong, it simply rarely gets explained fully.
08-26-2009, 10:54 PM   #4
Veteran Member




Join Date: Jul 2007
Location: Melbourne, Australia
Photos: Gallery
Posts: 394
Hi There,

It might be easier to say that DOF (at any one Fstop) is the same a focal length @ the same focal distance on any format.

DOF = FL x FD

Its just that FOV is different for each format at the same focal length, therefore if you want the same FOV in different formats, you must use different focal lengths and as you increase the size of the format, so do you increase the focal length.

EG:
FOV = 100mm ~ (6x7) = 50mm ~ (35mm) = 35mm (APSC) ~ (roughly speaking)

The greater the focal length for the same distance the smaller the DOF.
Again, DOF is related directly to focal length and distance NOT format.

So if you are keeping the same FOV across the different formats then you are changing the focal length of the lens in each format - therefore you are changing the DOF.

Cheers Neil

08-27-2009, 10:23 AM   #5
Veteran Member
troyz's Avatar

Join Date: May 2008
Posts: 389
QuoteOriginally posted by MJB DIGITAL Quote
Well I learned in the last thread that the time of exposure isnt changed by the size of the format.

But I do know that the DOF is thinner.

So if you were shooting a bit longer of a focal length--in available light--and you needed to open up your lens to a wider aperture, you might have too thin of DOF....

is that right?
You are correct in the case where you are forced to use the same exposure time (for example, because your subject is in motion or you're using a long lens without a tripod) and the same film in both formats, and the lenses used in each format have the same angle of view.

In practice, you would stop down to a smaller aperture setting (greater f/ number) to get the DOF you need, and use faster film or a longer exposure time to compensate.

BTW, check out Ctein's "Depth of Field Hell" articles on The Online Photographer when you get a chance.
08-27-2009, 01:12 PM   #6
Veteran Member




Join Date: Dec 2006
Location: Copenhagen
Photos: Gallery
Posts: 1,845
QuoteOriginally posted by MJB DIGITAL Quote
Well I learned in the last thread that the time of exposure isnt changed by the size of the format.

But I do know that the DOF is thinner.

So if you were shooting a bit longer of a focal length--in available light--and you needed to open up your lens to a wider aperture, you might have too thin of DOF....

is that right?
This is were people arguing for larger format, state that you simply shoot the e.g. FF camera with a stop higher Iso instead. This helps for you to stop down more, and get the DOF you want.
08-27-2009, 06:15 PM   #7
Forum Member




Join Date: Aug 2008
Location: Dallas
Posts: 98
For a given composition, larger formats are slower. It's simple physics. This is why some people used to argue that 35mm was just as good as medium format because at any given DOF and shutter speed, you could have 1-2 stop slower film in the 35mm camera and thus the grain would be comparable to medium format. The point is sound and it's why low light calls for small formats. When there is enough light, or shutter speeds can be long, larger formats still dominate.

It's also the reason FF digital cameras are dumb. The small sensor size of APS digital cameras allows lower iso to be used for any given DOF and shutter speed.
08-28-2009, 10:20 AM   #8
Site Supporter




Join Date: Feb 2008
Location: MT
Posts: 1,077
From a field work analysis, you'll likely notice a slimmer dof with medium format. This is not to say all the previous posts aren't correct--they are accurate.

For the landscape and macro work that I use medium format for, I find that I need to check dof carefully with the dof preview and I find that I need to stop down farther with medium format than with either 35mm or digi.

For example, landscape work without an exaggerated foreground can be done nicely in 35mm terms at f8 and f11 and still get the entire frame in focus--from say 25 ft to infinity. With medium format, I've found that the dof forces stopping down to f16ish and with any kind of foreground in the near frame area, stopping clear down to f22 is often needed. It's noticeable on the film as well as in the dof preview. I commonly use hyperfocal distance charts and hyperfocal markings on the lenses (available on all the Pentax 67 lenses). Still, getting the "near to far" perspective in focus is more difficult with medium format than with smaller formats. Note that large formats bigger than medium format almost always encorporate movements into the camera to allow for dialing in the zone of focus as simply stopping down may not be enough when the formats get larger.

So even though formulas and frame matching studies would perhaps suggest less difference in dof between formats...actual field situations for landscape shots which often require the full frame from near to far to be in focus would suggest that you should stop down farther with medium format than with the smaller formats. This is my experience in the field whether supported by the math or not.

With macro the differences may be even more noticeable as it's damn hard to get enough in focus with 1:1 lifesize work on 67. Pretty much have to use f22 or you won't like the amount of defocused area in the resulting photo. Yep, that 100mm Macro on 67 doesn't frame the same way my 100mm or 200mm macros frame on the smaller format, but my concern in the field is getting the flower in focus, not comparing formats. And yes, I shoot some wide open macro work to purposely defocus the background and isolate the subject, but where I notice the biggest difference between formats in the field is when shooting either landscape or macro shots that require most or all of the frame to be in focus.

Tight f stops bring up the potential for diffraction effect as the light entering the lens has to bend around the diaphram blades. Diffraction problems in my usage are far more noticeable through my 35mm and digi bodies than with stopped down medium format lenses. I suspect that this is because the diaphram blades are farther away from the film/sensor with medium format lenses thus reducing the angle of the bend necessary for the light to go past the tiny opening in the blades, yet still bend back out to fill the whole frame. Diffraction isn't caused by the tiny opening in the lens, but by the angle required for the light to spread back out and fill the frame on the film or sensor. Even with the larger frame size with medium format, the less acute angle of the light passing the aperture seems to control diffraction better than in smaller formats. Note that large format 4x5 inch and larger photography is often done with f stops as tight as f64 without undue diffraction effects, so regardless of the explanation or mathematical formulas to prove it...in the field, medium format and large format photography tolerates tighter f stops better than 35mm or APS-C digi work.

Again, I'm not disputing the factual explanations provided by other posts. Those posts are correct. But I'm pointing out that in field situations and on-the-film results, my personal experience is that medium format has much thinner dof than smaller formats and also has more tolerance to stopping down without undue diffraction. So really, I'm saying that for sharp images from foreground to infinity stop down tighter with medium format than what you are used to stopping down with smaller formats and don't fret about the risk of diffraction...it'll work out fine!

08-31-2009, 12:41 PM   #9
Veteran Member
MJB DIGITAL's Avatar

Join Date: Jul 2007
Location: st. louis
Posts: 1,173
Original Poster
QuoteOriginally posted by Ron Boggs Quote
From a field work analysis, you'll likely notice a slimmer dof with medium format. This is not to say all the previous posts aren't correct--they are accurate.

For the landscape and macro work that I use medium format for, I find that I need to check dof carefully with the dof preview and I find that I need to stop down farther with medium format than with either 35mm or digi.

For example, landscape work without an exaggerated foreground can be done nicely in 35mm terms at f8 and f11 and still get the entire frame in focus--from say 25 ft to infinity. With medium format, I've found that the dof forces stopping down to f16ish and with any kind of foreground in the near frame area, stopping clear down to f22 is often needed. It's noticeable on the film as well as in the dof preview. I commonly use hyperfocal distance charts and hyperfocal markings on the lenses (available on all the Pentax 67 lenses). Still, getting the "near to far" perspective in focus is more difficult with medium format than with smaller formats. Note that large formats bigger than medium format almost always encorporate movements into the camera to allow for dialing in the zone of focus as simply stopping down may not be enough when the formats get larger.

So even though formulas and frame matching studies would perhaps suggest less difference in dof between formats...actual field situations for landscape shots which often require the full frame from near to far to be in focus would suggest that you should stop down farther with medium format than with the smaller formats. This is my experience in the field whether supported by the math or not.

With macro the differences may be even more noticeable as it's damn hard to get enough in focus with 1:1 lifesize work on 67. Pretty much have to use f22 or you won't like the amount of defocused area in the resulting photo. Yep, that 100mm Macro on 67 doesn't frame the same way my 100mm or 200mm macros frame on the smaller format, but my concern in the field is getting the flower in focus, not comparing formats. And yes, I shoot some wide open macro work to purposely defocus the background and isolate the subject, but where I notice the biggest difference between formats in the field is when shooting either landscape or macro shots that require most or all of the frame to be in focus.

Tight f stops bring up the potential for diffraction effect as the light entering the lens has to bend around the diaphram blades. Diffraction problems in my usage are far more noticeable through my 35mm and digi bodies than with stopped down medium format lenses. I suspect that this is because the diaphram blades are farther away from the film/sensor with medium format lenses thus reducing the angle of the bend necessary for the light to go past the tiny opening in the blades, yet still bend back out to fill the whole frame. Diffraction isn't caused by the tiny opening in the lens, but by the angle required for the light to spread back out and fill the frame on the film or sensor. Even with the larger frame size with medium format, the less acute angle of the light passing the aperture seems to control diffraction better than in smaller formats. Note that large format 4x5 inch and larger photography is often done with f stops as tight as f64 without undue diffraction effects, so regardless of the explanation or mathematical formulas to prove it...in the field, medium format and large format photography tolerates tighter f stops better than 35mm or APS-C digi work.

Again, I'm not disputing the factual explanations provided by other posts. Those posts are correct. But I'm pointing out that in field situations and on-the-film results, my personal experience is that medium format has much thinner dof than smaller formats and also has more tolerance to stopping down without undue diffraction. So really, I'm saying that for sharp images from foreground to infinity stop down tighter with medium format than what you are used to stopping down with smaller formats and don't fret about the risk of diffraction...it'll work out fine!
I'm basking in your post. I love it.
That is exactly the kind of light I wanted shed on this subject.
Daaaaamn that was good!!

Thanks
Mitch

(p.s. Melissa can I also have a pentax 645n2 with a wide a mid and a long, all fast? throw in a light system and extra backs....) thanks

Last edited by MJB DIGITAL; 08-31-2009 at 12:43 PM. Reason: planning for christmas
08-31-2009, 01:03 PM   #10
Veteran Member




Join Date: Dec 2006
Location: Copenhagen
Photos: Gallery
Posts: 1,845
QuoteOriginally posted by Ron Boggs Quote
Tight f stops bring up the potential for diffraction effect as the light entering the lens has to bend around the diaphram blades. Diffraction problems in my usage are far more noticeable through my 35mm and digi bodies than with stopped down medium format lenses. I suspect that this is because the diaphram blades are farther away from the film/sensor with medium format lenses thus reducing the angle of the bend necessary for the light to go past the tiny opening in the blades, yet still bend back out to fill the whole frame. Diffraction isn't caused by the tiny opening in the lens, but by the angle required for the light to spread back out and fill the frame on the film or sensor. Even with the larger frame size with medium format, the less acute angle of the light passing the aperture seems to control diffraction better than in smaller formats. Note that large format 4x5 inch and larger photography is often done with f stops as tight as f64 without undue diffraction effects, so regardless of the explanation or mathematical formulas to prove it...in the field, medium format and large format photography tolerates tighter f stops better than 35mm or APS-C digi work.

Again, I'm not disputing the factual explanations provided by other posts. Those posts are correct. But I'm pointing out that in field situations and on-the-film results, my personal experience is that medium format has much thinner dof than smaller formats and also has more tolerance to stopping down without undue diffraction. So really, I'm saying that for sharp images from foreground to infinity stop down tighter with medium format than what you are used to stopping down with smaller formats and don't fret about the risk of diffraction...it'll work out fine!
Thanks for the detailed report, very interesting
08-31-2009, 02:29 PM   #11
Forum Member




Join Date: Aug 2008
Location: Dallas
Posts: 98
QuoteQuote:
So really, I'm saying that for sharp images from foreground to infinity stop down tighter with medium format than what you are used to stopping down with smaller formats and don't fret about the risk of diffraction...it'll work out fine!
This is good advice, and it goes the same for large format. However, slower f/stops are slower on any format. So at the end of the day, larger formats are slower given the same image composition.
09-01-2009, 10:23 AM   #12
Site Supporter




Join Date: Feb 2008
Location: MT
Posts: 1,077
Glad you found the post useful!

When I added 67 to my kit, and after a couple decades of shooting 35mm, I can't tell you how many times I missed the focus on the foreground. Here I had purchased a killer landscape tool and my images didn't reflect that fact...My initial macro work with medium format really sucked--and I had been selling 35mm macro work to magazines for years prior. FAILURE FORCED ME TO REEXAMINE DEPTH OF FIELD resulting in the beliefs outlined in the post...and resulting in a much more strict shooting technique with more attention to detail like hyperfocal distance and even bracketing focal point (one shot focused a hair closer than the other--just to cover for imperfect viewing in the dof preview).

When I started playing with digi--after a few years with the 67--the diffraction issues were pretty obvious. If I tried to stop down as far as I normally did with medium format, the diffraction blur was quite noticeable--even more so than with 35mm. Killer lenses like the FA*200 Macro produced crap images stopped down to f16, while that same lens did great work at f16 on 35mm film. And the Macro for my 67 barely had any dof at f16 and even at f22 seems skinny on the dof...and without obvious or terrible diffraction issues...

I'm still in the multi-year learning curve with the Zoerk Multi-Focus System which is an enlarger lens mounted to an adjustable mount allowing for extreme amounts of tilt movement--up to 40 degrees--on my 67II. And I adapted it for landscape and 1:1 macro work. Someday I'll shoot something useful with it...I probably only shoot a few rolls through it annually so it will take awhile to get good with it...that's a whole different issue.
09-01-2009, 12:28 PM   #13
Senior Member




Join Date: Nov 2008
Location: Honolulu
Posts: 150
Hey Ron,
People will go to all kinds of measures to increase the DOF with their 67's. There's a Bay area Physicist/ photographer named Leping Zha who loosenened the mounts of his 55mm lenses and put shims in, creating a lens with a permanent tilt, for increased DOF in near/far compositions. He has two, one for verticals and one for horizontal shots.
It's too bad Pentax never made a WA tilt lens for the 67, it would have been very popular with the landscape shooters.
09-02-2009, 12:31 PM   #14
Pentaxian




Join Date: Jul 2009
Location: Seattle
Posts: 7,103
What's all this talk of DOF in MF? Gee whiz, guys, the DOF scale is right there on the lens!
09-03-2009, 08:25 PM   #15
Veteran Member




Join Date: Dec 2006
Location: Copenhagen
Photos: Gallery
Posts: 1,845
Salgado is touring the world with a Pentax 645N. Here are two shots, showing the importance of enough DoF :
Salgado Antarctica 4 | | guardian.co.uk Arts

http://arts.guardian.co.uk/salgado/image/0,,1519337,00.html

QuoteOriginally posted by surfotog Quote
Hey Ron,
People will go to all kinds of measures to increase the DOF with their 67's. There's a Bay area Physicist/ photographer named Leping Zha who loosenened the mounts of his 55mm lenses and put shims in, creating a lens with a permanent tilt, for increased DOF in near/far compositions. He has two, one for verticals and one for horizontal shots.
It's too bad Pentax never made a WA tilt lens for the 67, it would have been very popular with the landscape shooters.
Doesn't the Hartblei lenses work for Medium Format ?
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, format, medium format
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Abstract My Right Foot johnmflores Photo Critique 3 05-31-2010 04:27 AM
Rebuilding the 35 MM Format FA* line to the DA* APS-C Format Adrian Owerko Pentax SLR Lens Discussion 14 01-20-2010 11:04 AM
my right foot. dcmsox2004 Post Your Photos! 10 08-16-2009 04:57 PM
Speed of a Larger Format MJB DIGITAL Pentax Medium Format 14 08-10-2009 02:54 AM



All times are GMT -7. The time now is 12:44 AM. | 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