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03-17-2011, 10:39 AM   #1
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Hyperfocal adjustment on current vs manual lenses

I've done some searching and haven't been able to find the answer to this one. From what I understand when setting hyperfocal for manual lenses on a crop sensor you need to advance the ring at least one stop larger and a little past. So if I'm setting up hyperfocal for f/11, I line up the infinity symbol a little past f/8.

The question I have, do you need to do this also with modern lens builds? For example the DA 21 is listed as "Not suitable for 35mm film SLR cameras." So if the lens is designed for crop sensors, do you still have to offset the hyperfocal setting or is f11, f11 on a DSLR?

Another example, the DA 15. From what I can tell it works with both 35mm SLR and DSLR. So does the lens follow the 35mm hyperfocal standard or a DSLR standard?
Thanks,

03-17-2011, 11:44 AM - 1 Like   #2
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I think you have it figured out... My understanding is that DOF scales on lenses "designed for crop sensors," i.e. Pentax DA lenses, are proper for crop sensors and don't need to be adjusted. If there are DOF scales on DFA lenses then I don't know
03-17-2011, 11:50 AM   #3
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Sensor size does not affect hyperfocal distance of a lens. It is the same no matter what format you put it on. The sensor size affects the field of view you're getting with a lens but not it's depth of field, hence it cannot change the hyperfocal distance.


Good chart that shows this
03-17-2011, 11:58 AM   #4
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Sorry Jim that is only valid for FF
hyperfocal distance can be compared at the online DOF calculator (it likely won't be perfect but it'll give you the zone of focus pretty closely)

for example crop sensor focal point 10 ft f11 on a 50mm lens in focus zone will be Close Limit 7.87 ft
Far limit 13.7 ft
Total 5.86 ft

The same lens on FF/35mm will be
Close Limit 7.11 ft
Far limit 16.9 ft
Total 9.76 ft

At f 8 the 35mm is
Near limit 7.77 ft
Far limit 14 ft
Total 6.28 ft

So pretty much as you are expecting DOF scale is off by about one stop on the lens (a little more actually the closest would be to set it nearer f 7.1 which is 5.49 ft in focus)

It's a pretty cool little web page, it's interesting to compare FOV across formats versus the DOF. my 40mm f 4.0 on my 645 has razor thin DOF compared to my 14 f2.8 or my 21 f3.5 on digital and 35 respectively but presents close to the same FOV

Online Depth of Field Calculator

03-17-2011, 12:02 PM - 1 Like   #5
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QuoteOriginally posted by Jimfear Quote
Sensor size does not affect hyperfocal distance of a lens. It is the same no matter what format you put it on. The sensor size affects the field of view you're getting with a lens but not it's depth of field, hence it cannot change the hyperfocal distance.


Good chart that shows this
If you expect a constant print size then the hyperfocal distance does change with sensor size because the enlargement differs.

For example see Online Depth of Field Calculator

For example from the link:
Canon 7D 55 f:16 Hyperfocal distance = 32.8 feet (Full frame CoC = 0.019mm)
Canon 5D 55 f:16 Hyperfocal distance = 20.9 feet (Crop frame CoC = 0.03mm)

Dave

PS it is because the Circle of Confusion size used in calculations depends on assumptions about how the photo will be displayed; CoC's are in the same ratio as sensor sizes for constant display width.
03-17-2011, 12:07 PM   #6
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for an explanation of the calculations. Pentax Circle of confusion is .020, FF is .030. equation is at link

http://www.dofmaster.com/equations.html
03-17-2011, 12:13 PM   #7
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The way I remember is to think that if I enlarge more (as will be the case with a crop sensor) then slightly OOF areas will be more obvious, reducing apparent DOF.
03-17-2011, 12:16 PM   #8
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QuoteOriginally posted by sewebster Quote
The way I remember is to think that if I enlarge more (as will be the case with a crop sensor) then slightly OOF areas will be more obvious, reducing apparent DOF.
thanks, that takes the geekiness out of the equation nicely and is bang on.

I do look at the DOF calculator as a means of improving some technique myself (useful for knowing when a hip shot or a high over the head shot has a hope of working out - not at the time of the shot just a means of better knowing my gear)

03-17-2011, 12:48 PM   #9
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QuoteOriginally posted by eddie1960 Quote
Sorry Jim that is only valid for FF
hyperfocal distance can be compared at the online DOF calculator (it likely won't be perfect but it'll give you the zone of focus pretty closely)

Online Depth of Field Calculator
Logical experiment. With the same lens, if you aim your camera at a ruler lying on a table and take one photo with a FF camera and one with an APSC camera with the same settings (centre of ruler is the focus point and then it fades into bokeh in front and behind that). What you are in effect doing with the APSC is cropping out a smaller frame in the middle of the FF picture. So the absolute DOF will be the same in the two photos, right? I would be very surprised if the picture taken with the APSC had a shorter absolute DOF.

If there isn't something very fishy going on here the hyperfocal distance should not change because of capture format. Now I understand that circle of confusion might just be that fishy thing so I guess I should read up on the physics behind this to be sure.

Or then if someone with a nikon FF could just take the pics in the above mentioned experiment using the autocrop function the camera has and post them here.



QuoteOriginally posted by sewebster Quote
The way I remember is to think that if I enlarge more (as will be the case with a crop sensor) then slightly OOF areas will be more obvious, reducing apparent DOF.
This is a very good way of thinking about it, makes it much more logical.

Think I might be getting a hang of CoC now. Will leave the above text standing though because I'd still want someone to take the pics and compare them, 1-0 to physics if there is actually a difference.
03-17-2011, 01:03 PM   #10
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it would take me some time but i could do a comparative shot with film 35mm film versus apsc digital. but in reality the COC of the various film plane sizes is the reason for the difference. One of the reasons you don't see faster than f2.8 medium format lenses is they would be near impossible to focus. same reason you fdon't see fast large format lenses

for example If I shoot a 150 on my 645 at f4.0 from 8 feet (so a portrait, the 150 is about the same as a 90) my in focus zone will be about 3 inches (.29 feet)
if the lens was capable of 1.4 like the *85 and i shot it wide open there would be less than an inch in focus a the same distance, whereas on 35mm the 1.4 wide open has about the same in focus zone as the 645 at f4.0
DOF control is one of the reasons for moving up to bigger sensors or medium format or larger. If you are doing studio work with lots of light it's very nice to still be able to achieve the narrow DOF. the reason so many wedding guys also shot MF (that and print size) (on 4x5 film it would be a 250 at f 5.6 for the same effect essentially)

Since DOF and Hyperfocal distance are directly related thus the difference. if you really want wide in focus areas then a m4/3 would be even better
03-17-2011, 01:39 PM   #11
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before everyone goes off in their own direction. there are a lot of half correct things here, so lets get it all out on the table/

The issues surrounding not only depth of field, but also the rule of thumb for shutter speed (1/focal length) for a 35mm camera, do not change AT ALL, when going to a cropped sensor, providing the magnification from sensor/film, to paper remains unchanged.

If yo consider film, these rules and DOF markings are based on a circle of cofusion of 0.030 mm when projected onto a 8 x 10 print.

take a shot on film, print to 8 x 10, then cut the middle 5 x 7 out of that frame, nothing changes. Now take the same shot from the same position using a DSLR and pring it to 5 x 7, it will be identical in every respect. BUT... if you increase the enlargement of the film frame by 50% or print the digital frame to 8 x 10 then DOF appears to become less.

The same holds true for shutter speed and camera shake.

What is important to note here is that it is the final ratio subject to print that is important in DOF not the intermediate steps.
03-17-2011, 02:07 PM   #12
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I agree lowell but people rarely think in terms of print now since (sadly) most pics never get viewed beyond a computer monitor
8x10 is a reasonable asdumption of print size now since almost everyon xan print it at home
Personally i print 11x14 or larger but will occasionally run a large batch of 4x6 as a backup to digital
But i am far from the norm i think
03-17-2011, 03:26 PM - 1 Like   #13
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QuoteOriginally posted by eddie1960 Quote
I agree lowell but people rarely think in terms of print now since (sadly) most pics never get viewed beyond a computer monitor
8x10 is a reasonable asdumption of print size now since almost everyon xan print it at home
Personally i print 11x14 or larger but will occasionally run a large batch of 4x6 as a backup to digital
But i am far from the norm i think
But if no one prints 8x10 any more and enlarges to higher magnifications then the whole discussion is TOTALLY USELESS because the lens markings have no relevance.
03-17-2011, 03:34 PM   #14
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QuoteOriginally posted by eddie1960 Quote
for example If I shoot a 150 on my 645 at f4.0 from 8 feet (so a portrait, the 150 is about the same as a 90) my in focus zone will be about 3 inches (.29 feet)
if the lens was capable of 1.4 like the *85 and i shot it wide open there would be less than an inch in focus a the same distance, whereas on 35mm the 1.4 wide open has about the same in focus zone as the 645 at f4.0
DOF control is one of the reasons for moving up to bigger sensors or medium format or larger. If you are doing studio work with lots of light it's very nice to still be able to achieve the narrow DOF. the reason so many wedding guys also shot MF (that and print size) (on 4x5 film it would be a 250 at f 5.6 for the same effect essentially)

Since DOF and Hyperfocal distance are directly related thus the difference. if you really want wide in focus areas then a m4/3 would be even better
But you haven't thought this through now. What focal lengths that roughly equate each other on different formats and how they produce DOF has nothing to do with the question at hand, if the stated hyperfocal distance for a given lens on a given format holds true when used on another format.


QuoteOriginally posted by Lowell Goudge Quote
before everyone goes off in their own direction. there are a lot of half correct things here, so lets get it all out on the table/

The issues surrounding not only depth of field, but also the rule of thumb for shutter speed (1/focal length) for a 35mm camera, do not change AT ALL, when going to a cropped sensor, providing the magnification from sensor/film, to paper remains unchanged.

If yo consider film, these rules and DOF markings are based on a circle of cofusion of 0.030 mm when projected onto a 8 x 10 print.

take a shot on film, print to 8 x 10, then cut the middle 5 x 7 out of that frame, nothing changes. Now take the same shot from the same position using a DSLR and pring it to 5 x 7, it will be identical in every respect. BUT... if you increase the enlargement of the film frame by 50% or print the digital frame to 8 x 10 then DOF appears to become less.

The same holds true for shutter speed and camera shake.

What is important to note here is that it is the final ratio subject to print that is important in DOF not the intermediate steps.
Yes so what we should really be concerned with here is at what magnification this will be viewed. As the COC that the markings are based on only holds true under specific conditions we can say that depending on the magnification the focus distance needed at a specific f-stop to produce hyperfocus will vary from under to over what the markings indicate.

QuoteOriginally posted by Lowell Goudge Quote
DOF appears to become less
I highlight this as this is the heart of the matter. DOF will stay absolutely the same, but it will be perceived as having changed.
03-17-2011, 03:36 PM   #15
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QuoteOriginally posted by Jimfear Quote
Logical experiment. With the same lens, if you aim your camera at a ruler lying on a table and take one photo with a FF camera and one with an APSC camera with the same settings (centre of ruler is the focus point and then it fades into bokeh in front and behind that). What you are in effect doing with the APSC is cropping out a smaller frame in the middle of the FF picture. So the absolute DOF will be the same in the two photos, right? I would be very surprised if the picture taken with the APSC had a shorter absolute DOF.
Well, it probably depends on your definition of "absolute DOF." Theoretically, the DOF is always zero. There is always only one place that is in "perfect" focus. However, based on certain factors like, how good your eyes are, what type of sensor you use, how you view the image etc., there is a region that you can't tell the difference between "perfectly" in focus and "very slightly" out of focus. This is what we call the DOF.

For your example with the ruler, definitely the picture taken with the crop sensor and then enlarged (either in print, or viewed on a computer monitor) to the same physical size will _appear_ to have less DOF. The "true" DOF in both cases is zero. Don't get too hung up on my terminology here though. DOF is basically defined as what we perceive with a certain set of assumptions.

PS I am a physicist
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