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Sensor size and Hyperfocal range (with the same lens)

gerald.d

Well-known member
That's why I don't read other people's theoretical articles. I test for myself. :)

If it didn't make any difference, then why all these insane debates about why FourThirds format doesn't give you the ability to make shallow depth of field, why FF lets you get beautiful bokeh, why MFD gives you such shallow and controllable DoF, etc etc?
Because the larger the sensor, the greater the field of view for a given focal length.

The only thing that has a bearing on perspective is absolute subject distance.

Therefore, for a given subject distance and desired framing, the larger format enables you to use a longer focal length lens.

Longer focal length, same subject distance, shallower depth of field.

At least, that's the way I've always looked at it.

Kind regards,


Gerald
 

gerald.d

Well-known member
OMG - look into a pit and dive into it ...

Hyperfocal effectiveness is based on prints, not necessarily pixel peeping. If you pixel peep, use root(2) x pixel pitch for sharpness considerations. If you look at real photos printed on real paper, use the traditional calcs for viewing the prints and just relax. Heck even the DoF scale on your lens will work out just fine.

If you pixel peep, you'll just be disappointed and frustrated with your 1mm in focus region. :facesmack:
I think it's a little condescending to dismiss anything that isn't printed. The vast, vast majority of photos taken nowadays (whether you consider them real or not) will never be printed. And why should we limit ourselves to viewing images at a proscribed distance?

Pixel peeping has its place, surely?

Kind regards,

Gerald.
 

Godfrey

Well-known member
I think it's a little condescending to dismiss anything that isn't printed. The vast, vast majority of photos taken nowadays (whether you consider them real or not) will never be printed. And why should we limit ourselves to viewing images at a proscribed distance?

Pixel peeping has its place, surely?

Kind regards,

Gerald.
While I generally do my testing and evaluation of DoF with prints in mind, I don't eschew digital presentation at all. HOWEVER, the same principles apply ... and they're not 'pixel-peeping'. When I'm judging a photo for printing, I display it at a size similar to the print size on my display ... I usually print 6x8 or 8x8 on 8.5x11 paper, or 9x15 on 11x17 paper, or similar. So it's easy to simulate the actual DoF that the prints will have that way with a 27" display.

I do a similar thing when evaluating photos I'm going to put on my iPhone or iPad ... I check them at the display size. DoF varies and sometimes I need to soften the image for these small display spaces in order to achieve the look I want. And sometimes I need to reduce the photo in several small stages for these platforms because the 'all at once' interpolation down from a 24 Mpixel image to a iPhone display leaves a lot of ugly mess behind and looks terrible.

I didn't find Graham's comments condescending. Pixel-peeping (the act of excruciating inspection of photographs at 1:1 pixel magnification) is worthless to determine DoF and the overall look of either a printed image or of a well-presented digital image on a display. It's a great way to make specious arguments about the so-called "image quality" of lenses, however. :cool:

G
 

gerald.d

Well-known member
While I generally do my testing and evaluation of DoF with prints in mind, I don't eschew digital presentation at all. HOWEVER, the same principles apply ... and they're not 'pixel-peeping'. When I'm judging a photo for printing, I display it at a size similar to the print size on my display ... I usually print 6x8 or 8x8 on 8.5x11 paper, or 9x15 on 11x17 paper, or similar. So it's easy to simulate the actual DoF that the prints will have that way with a 27" display.

I do a similar thing when evaluating photos I'm going to put on my iPhone or iPad ... I check them at the display size. DoF varies and sometimes I need to soften the image for these small display spaces in order to achieve the look I want. And sometimes I need to reduce the photo in several small stages for these platforms because the 'all at once' interpolation down from a 24 Mpixel image to a iPhone display leaves a lot of ugly mess behind and looks terrible.

I didn't find Graham's comments condescending. Pixel-peeping (the act of excruciating inspection of photographs at 1:1 pixel magnification) is worthless to determine DoF and the overall look of either a printed image or of a well-presented digital image on a display. It's a great way to make specious arguments about the so-called "image quality" of lenses, however. :cool:

G
When I print, I typically print 60x40. And people examine those prints with their nose pretty much touching them. So it's kinda important - to me - to "pixel peep" to ensure that the things I want in focus, are in focus - and not just appear to be in focus from 6 feet away.

Here's a 100% crop from an 80MP image that will be printed.



Of course if you're 6 feet away you're never going to see that detail. But it is important to me that the detail is there should someone want to go looking for it.

For digital display, I routinely create multi-gigapixel images.

Here's an example.

http://dubai360.com/#!s=1313-burj-khalifa-pinnacle-45-gigapixels&l=en

Pixel peeping is not "worthless" to determine either DoF or the overall look of an image, if you're prepared to take a leap of faith and accept the fact that not everyone is in the business of creating small prints that are only ever to be viewed from a proscribed distance.

Kind regards,


Gerald.
 

ErikKaffehr

Well-known member
Hi,

I would add that diffraction also sets a limit. No idea to stop down beyond Airy circle size being similar to CoC?

Best regards
Erik


However it also lets the circle of confusion change, and that is the real reason why the calculated DOF changes.

If you enlarged both images by the same factor, clearly the DX print will be smaller than the FX print, but the DOF will be the same in both.

That calculator is not based on equal enlargements/magnifications, but on equal print sizes; and when you enlarge a smaller-sensor image by a larger factor to match the print sizes, you also enlarge the impression of blurriness in the areas just fore and aft of the plane of focus. The calculator adjusts for this by imposing a smaller limit to the circle of confusion in the original capture. You are now judging the same image projected by the same lens [in the areas where the sensors overlap] by a harsher criterion. But that is what the eye's tolerance for unsharpness demands from equal print sizes.

So, back to Chris' original question: "would the area of focus be greater if using the same lens on a smaller sensor and focusing at the same distance at F8?"
Answer: No. It will be either the same, or smaller. The same, if you enlarge them by the same factor, and end up with a smaller print from the smaller sensor. Smaller, if you enlarge them to the same print size.

Ray
 

Godfrey

Well-known member
When I print, I typically print 60x40. And people examine those prints with their nose pretty much touching them. So it's kinda important - to me - to "pixel peep" to ensure that the things I want in focus, are in focus - and not just appear to be in focus from 6 feet away.

Here's a 100% crop from an 80MP image that will be printed.

...
If you're going to print to 60x40 inches (really? or do you mean centimeters? 60x40cm == 23x15 inch) and you expect people to be examining the prints with a magnifying glass, none of the calculators or DoF scales are going to give you realistic DoF numbers since the scales and calculations are always based on something like an 8x10 inch print viewed at about 18 inches distance.

The only thing you can do in that instance is make a print and see if it suits your focus requirements.

Pixel peeping does little to help since looking at pixels on a display screen isn't anything like looking at an image printed by ink on paper. The sample clip you showed me tells me nothing about whether the photo is in or out of focus, or has the right focus zone, etc.

sorry,
G
 

gerald.d

Well-known member
If you're going to print to 60x40 inches (really? or do you mean centimeters? 60x40cm == 23x15 inch) and you expect people to be examining the prints with a magnifying glass, none of the calculators or DoF scales are going to give you realistic DoF numbers since the scales and calculations are always based on something like an 8x10 inch print viewed at about 18 inches distance.

The only thing you can do in that instance is make a print and see if it suits your focus requirements.

Pixel peeping does little to help since looking at pixels on a display screen isn't anything like looking at an image printed by ink on paper. The sample clip you showed me tells me nothing about whether the photo is in or out of focus, or has the right focus zone, etc.

sorry,
G
Yes. Inches. As a minimum.





But no - people do not use magnifying glasses.

The level of condescension is overwhelming.

I give up.
 

Godfrey

Well-known member
Yes. Inches. As a minimum.
But no - people do not use magnifying glasses.
The level of condescension is overwhelming.
I give up.
Sorry you feel that way. There's no condescension intended in my statements.

If you're printing that big, and expect people to look at the prints at close up distances, there are no calculations available that will give you a realistic assessment of the resulting overall DoF. Or rather, you're going to have to run your own calculations using a CoC adjusted for such extraordinary magnification and consider focus zone on a local scale, not across the entire image field (the standard use of the term DoF), ignoring the commonly used scales and calculators ... they're meaningless for such work.

And I simply don't believe there's any usefulness in examining such images at 1:1 pixel magnification for DoF at all. It doesn't net you any useful appreciation of the DoF, which has been the subject of this thread. Examining an 80 Mpixel image at 1:1 pixel magnification can tell you that this bit in front of you that you're looking at now is suitably sharp, or not, and that's about it. That's not an evaluation of DoF according to any standard definition of the term.

You're in a space of "special circumstances": the standard measures are not useful for those circumstances.

G
 

GrahamWelland

Subscriber & Workshop Member
The level of condescension is overwhelming.

I give up.
Gerald

Definitely no condescension intended from this end.

For you it's obvious that CoC and viewing distance still come into play. In your case it's nose depth from the print so I would assume (without calculating it) that you're as near as damn it at pixel peep level for those prints. That in itself would make critical sharpness a challenge at MF and F stops that aren't subject to significant diffraction. The discussion of course is what is your acceptable depth of focus? As we know there is only one exact plane of focus and everything else in front or behind is just gradually getting softer and it's a question of whether that softness is visible or acceptably visible or not.

Like I mentioned though, this one is a rathole that always descends into strong opposing views and opinions about what is acceptable DoF. It never ends well ...

The best quote I ever heard on this was regarding the definition of "Circle of Confusion" - a bunch of photographers sitting around a table arguing over depth of focus/field calculations ... :chug:
 

ErikKaffehr

Well-known member
Hi,

I am aware of the CoC explanation you mention.

Two small reflections:

I was asked to do a presentation about the hyperfocal distance at our camera club. So I prepared two A2 size prints (16"x23") one with CoC based on lens markings on my Distagon 60/3.5 for the blad, the other with foreground in accurate focus. Close viewing there was a difference even a blind man could see, but just looking at normal viewing distance it was not obvious at all that the one print was better than the other.


The other observation is that I don't think we observe images at nose lengths distance. Human vision can normally focus to around 10", so that would be reasonable with full 20/20 vision and young eyes. Older persons cannot normally focus that close and corrective glasses are normally not made for close focusing distances. Personally, I am near sighted so I can view images quite close. What I see is that I tend to pixel peep A2 size images and larger at around 40 cm or 16", measured with a laser distance meter. Interestingly, it is often said that 180PPI is needed for an excellent print, that corresponds to 20/20 vision at 50cm/20".

Best regards
Erik


Gerald

Definitely no condescension intended from this end.

For you it's obvious that CoC and viewing distance still come into play. In your case it's nose depth from the print so I would assume (without calculating it) that you're as near as damn it at pixel peep level for those prints. That in itself would make critical sharpness a challenge at MF and F stops that aren't subject to significant diffraction. The discussion of course is what is your acceptable depth of focus? As we know there is only one exact plane of focus and everything else in front or behind is just gradually getting softer and it's a question of whether that softness is visible or acceptably visible or not.

Like I mentioned though, this one is a rathole that always descends into strong opposing views and opinions about what is acceptable DoF. It never ends well ...

The best quote I ever heard on this was regarding the definition of "Circle of Confusion" - a bunch of photographers sitting around a table arguing over depth of focus/field calculations ... :chug:
 

GrahamWelland

Subscriber & Workshop Member
Eric,

I'm so happy to know that you and I both agree. :thumbs:

20/20 vision imposes certain limitations (for me they're severe now close up but perfect at 3ft onwards).
 

Godfrey

Well-known member
Eric,

I'm so happy to know that you and I both agree. :thumbs:

20/20 vision imposes certain limitations (for me they're severe now close up but perfect at 3ft onwards).
I've never had perfect vision, but can get to 20/20 in my right eye and 20/30 in my left with correction still. It's not been a problem.

To me, discussing DoF means discussing the "apparent sharpness of a photograph", a global phenomenon, which is by no means the same thing as "evaluating a photograph's resolution", which is a local phenomenon. If you're not looking at the photograph as a whole, discussion of DoF is way off the mark and no amount of CoC calculations or pixel peeping has any meaning.

I don't know about anyone else, but I can't look at the whole of even a 13x19" print at much less than 30 inch distances... !

G
 
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