A difficult question - shooting square

[wolfloid]

Advertisement (gone after registration)

I've figured out that if I want to shoot with the same framing I can shoot at the same distance as my Rolleiflex with its 80/2.8 lens with a 35/1.4 asph and crop the sides to square. So far, so good.

 

However, if I look at depth of field calculator and calculate the depth of focus for the 6x6 camera at 2.5 metres, they tell me that I will get .24 metre in focus (seems a lot), which from experience gives me a very creamy background boke at about 3.5 metres (think full body environmental portrait, with closeish background). My experience of the real depth of focus at this distance with this camera is more like .10 metre at most.

 

I would like to be able to replicate this beautiful, shallow out-of-focus effect at the same distances on the monochrome 246 (which I do not yet own). However, using the 35/1.4 asph (which is the lens I need for the framing and distance, and which I do own), the same calculator tells me that at f1.4 I would get .43 metre in focus, in other words, double the depth of field, and far too much to give me an equivalent creamy boke. Somehow, I don't want to accept defeat here. Have I calculated anything incorrectly? Can anyone give me hope?

[Advertisement]

The Leica Q3 is available for pre-order at B&H Photo Video and Adorama

[a.noctilux]

You may not never obtain with 24x36 what you had (and like I think) with 6X6 .

 

Or try 50mm Summilux / Noctilux for something that could mimic what you want, but not with 35mm focal length.

 

Better yet Summilux-M 75mm if you can try one, you may find in photos that lovely creamy look .

[wolfloid]

Thanks. I know I can get a creamy look with a longer, fast lens. But I was wondering whether I could get it with the same perspective and framing as the Rolleiflex.

[pico]

Thanks. I know I can get a creamy look with a longer, fast lens. But I was wondering whether I could get it with the same perspective and framing as the Rolleiflex.

 

No. The larger format has greater gradation range.

.

[Michael Geschlecht]

Hello Wolfloid,

 

Welcome to the Forum.

 

IF you were to make a print from the 6 X 6 (Actually 56mm X 56mm.) & a print from the 24mm X 24mm center of the 24 X 36 format, with an 80mm lens on the 56 X 56 & a 35mm lens on the 24 X 24:

 

AND both lenses were focused to the same point (ie: 3 meters.) AND both apertures were set at the same number (ie: F8):

And both images were printed so that the objects photographed WERE THE SAME SIZE in millimeters, in the respective finished prints:

 

You would find that the 2 photos would be very similar:

EXCEPT that the photo originally taken on the 56 X 56 surface would be a better photo because it would contain more information: Since there were more square millimeters of surface area (56 X 56 = 3136 square millimeters. 24 X 24 = 576 square millimeters.):

 

to collect information on.

 

Everything else equal: More information on a given collecting surface will produce a better photo.

 

Best Regards,

 

Michael

[250swb]

Use a longer focal length lens and use those two things on the ends of your legs to transport you further away from the subject.

[fotomas]

Advertisement (gone after registration)

From Voigtländer there is the 35 mm / 1,2 Ultron that might have a smaller depth of field. But I hardly believe that this could be comparable with the Rolleiflex image.

[wolfloid]

"Use a longer focal length lens and use those two things on the ends of your legs to transport you further away from the subject."

 

Easier said than done in many of the place that I photograph - markets, and narrow streets. Even the 80mm Zeiss on the Rolleiflex is already often too long. Even so, the perspective also completely changes, and anyway I don't like long lenses much for the sort of work I do.

[wolfloid]

"You would find that the 2 photos would be very similar:

 

EXCEPT that the photo originally taken on the 56 X 56 surface would be a better photo because it would contain more information: Since there were more square millimeters of surface area (56 X 56 = 3136 square millimeters. 24 X 24 = 576 square millimeters.):"

 

Very similar in perspective, yes, but depth of focus? Looking at depth of field calculators shows a significant depth of field difference.

 

I'm also not talking about comparing 24x24 film to 56x56 film, but comparing the monochrome 246 24x24 output to the Rolleiflex.

[Jager]

...

 

Very similar in perspective, yes, but depth of focus? Looking at depth of field calculators shows a significant depth of field difference.

 

I'm also not talking about comparing 24x24 film to 56x56 film, but comparing the monochrome 246 24x24 output to the Rolleiflex.

 

You asked about how to achieve similar results using 35mm as when using your medium format rig.  Michael described how to do that.  And, yes, depth-of-focus would be similar.

[wolfloid]

"And, yes, depth-of-focus would be similar."

 

That is not at all obvious to me. Can you explain your reasoning?

[Michael Geschlecht]

Hello Wolfloid,

 

The reason that the 2 images, as described by me, would be similar, including their depth of field, is:

IF you enlarge both subjects to the same size in millimeters:

 

Which means less enlargement for the image captured on the 56mm X 56mm film or sensor surface:

And more enlargement on the 24mm X 24mm film or sensor surface:

Please keep in mind that whether the image is on a film surface or a sensor surface makes no difference in depth of field, etc:

 

Then the resultant images, including depth of field, should be pretty much the same.

 

This is because using a 35mm lens to cover a 24mm X 24mm image surface is close to the image surface coverage of an 80mm lens on a 56mm X 56mm image surface.

 

When you create an image the same size in millimeters of the same subject taken with 2 lenses, taken from the same distance, with both lenses set at the same F stop, regardless of their focal lengths, you get the same depth of field.

 

Because:

 

A 24mm X 24mm film/sensor image has to be magnified more times to be a certain size in millimeters than the image on a 56mm X 56mm film sensor does to create the same size image in millimeters in an equivalent photo.

 

And depth of field tables are based on magnification to some standardized size:

And the smaller original image has to be magnified more than the larger original image:

And as you magnify the image more, the depth of field for that specific image becomes less.

 

Regardless of what the marks on the lens or some depth of field table tells you.

 

The question that you are asking is: How to create THE SAME image size regardless of image collector surface size when you are using 2 different size image collector surfaces:

 

Best Regards,

 

Michael

Edited June 2, 2017 by Michael Geschlecht

[wolfloid]

If what you are saying is correct, then that is good news indeed.

 

However, I can't exactly visualise what you say and still have my doubts. What seems most odd to me is that you claim that as the samaller image is magnified the depth of field reduces. How can this happen?

 

Whether I look at an image taken using a 35mm at f1.4 projected/printed to six inches wide or 6 feet wide, it still has narrow depth of field - that is an affect of the distance I shoot from, the aperture, the particular lens focal length, and internal distances framed within the image. How does the depth of field change as it increases in size? The impression of separation remains exactly the same no matter how large I blow an image up.

 

It is the same if I use f8, if I take a photograph with everything in focus at 6 inches wide, won't everything also seem in focus when it is six feet wide?

 

I'm baffled.

[pico]

I've figured out that if I want to shoot with the same framing I can shoot at the same distance as my Rolleiflex with its 80/2.8 lens with a 35/1.4 asph and crop the sides to square. So far, so good.

 

However, if I look at depth of field calculator and calculate the depth of focus for the 6x6 camera at 2.5 metres, they tell me that I will get .24 metre in focus (seems a lot), which from experience gives me a very creamy background boke at about 3.5 metres (think full body environmental portrait, with closeish background).

 

 

Remain with what already works for you.

[luigi bertolotti]

However, I can't exactly visualise what you say and still have my doubts. What seems most odd to me is that you claim that as the samaller image is magnified the depth of field reduces. How can this happen?

 

...

I'm baffled.

CIRCLE OF CONFUSION ... Read a complete article about DOF (Michael post is already very good, but better to "start from scratch") , and take in right account how the CoC is important within the computation.

Edited June 2, 2017 by luigi bertolotti

[Michael Geschlecht]

Hello Luigi,

 

Thank you.

 

Hello Wolfloid,

 

The 'circle of confusion" That Luigi is referring to is:

 

"Depth of field" is simply: That degree of out of focus image that a person considers acceptable enough to consider as being in focus.

 

Because:

 

In reality: There is only 1 plane of best focus: This exists at a certain point at a right angle to the lens axis. 

 

Everything else, either in front of or behind this image plane: Is either slightly out of focus or even more out of focus. Depending on how far it is from the actual plane of focus.

 

Manufacturers choose a standard of what they think of as acceptable to be considered in focus.

 

Leitz/Leica & many others choose a point light source resolved as a disc no more than 1/30mm wide, film or sensor, as being acceptably in focus.

 

Marks indicating that is where the depth of field indicator marks are placed on their lens's barrels (Usually).

 

That is: The point where they think a mis-focused image will be seen as acceptably sharp.

 

Although not everybody agrees with this standard.

 

Best Regards Both,

 

Michael

[wolfloid]

How does 'the circle of confusion' address this:

 

Whether I look at an image taken using a 35mm at f1.4 projected/printed to six inches wide or 6 feet wide, it still has narrow depth of field - that is an affect of the distance I shoot from, the aperture, the particular lens focal length, and internal distances framed within the image. How does the depth of field change as it increases in size? The impression of separation remains exactly the same no matter how large I blow an image up.

[jaapv]

Michael's answers are correct, but a simplification of the complete story. For one thing, they don't take the type of lens into consideration. If one lens is a symmetrical design like many older lenses, and the other a modern asymmetrical one, there will be a considerable difference in DOF. ( http://toothwalker.org/optics/dofderivation.html )

 

https://groups.csail.mit.edu/graphics/classes/CompPhoto06/html/lecturenotes/22_DepthDefocus_6.pdf

[Advertisement]

Hallo,

Look here: Leica M

[pop]

A point is sharp or "in focus" if is shown in the image as a point; it's not sharp if it is shown as a small circle or (blurry) disc. However, whether a viewer can tell a blurry disc from a sharp point depends on a number of things: the eyesight of the viewer, the distance of the viewer from the print and the diameter of the blurry disc. Depth of field is defined as the range of distance that will produce images that will be perceived as sharp under "normal" conditions. Hence, magnifying an image will magnify the blurry discs as weill, thus making them seem even blurrier, unless the viewer moves away from the magnified print so that the apparent size of the print remains the same.

[wolfloid]

I think the circle of confusion argument is at cross purposes. I do understand it, I have been photographing for 40 years.

 

I will try to rephrase my scepticism over your argument that "you claim that as the samaller image is magnified the depth of field reduces" and my response - How can this happen?"

 

I don't think this question has been answered. I am talking about the relationship of sharp parts of the image to unsharp parts, in other words the effects of shallow depth of focus. If my image is shot on a 35mm Leica lens at f8 it will give me a very different depth of field, and depth of focus to an 80mm medium format lens shot at the same aperture both taken from the same distance (giving roughly equal framing - so 24x24 on the leica). The MF lens will yield a much shallower depth of field, in other words, the relationship of objects being sharp in the image to those being unsharp will have a much more obvious effect. This is a part of the image quality, not dependent on the size of the printed image.

 

Of course, as I blow each image up, what previously appeared in sharp focus, if viewed from the same distance, will gradually appear less sharp. To get the same sense of sharpness I would have to change my viewing distance - this is what COC is about -viewing distance and acceptable sharpness.

 

The internal relationships of what appears to be sharper and what appears to be very blurred or medium blurred does not change. At least not in the thousands of images I've printed.

 

If you think this is wrong, then I need a rational explanation for exactly why the depth of field charts (which give figures for the depth of focus related to objects within the image) are all wrong.