Technical question about a portrait by M. Quinn Jacobson

[Tobias Key]

Thx everyone!

Are you sure a long lens is part of the solution? I'm a bit sceptical about it... I was thinking dof only depends on two factors, lens aperture and growth factor. This last point depends on focal length relatively to focussing distance, and of course, film size... In other words: I was thinking you obtain the exact same dof with a shorter lens and a shorter distance. Only perspective problems may occur... but with the same head a shoulder shot, only the aperture and plate size may give a difference on dof.

And I saw this plate on youtube videos, it's not a huge mammoth plate... seems to be around 18x24...

It maybe this size of plate with a very fast lens...

There is the same effect on this plate:

Attachment 175364

I hope my future 2.8/150mm will allow me to approch this kind of images on 4x5 plates!

You achieve the same DOF with short and long lenses with the same reproduction ratio, but once you are outside that sharp zone long lenses blur off more quickly. So there is an illusion of less depth of field.

[Drew Wiley]

You'd have a different perspective even with a very fast 150, but it might work in a slightly different sense. Logistically, you might be uncomfortably close to the sitter.

[Pere Casals]

Theorically (DOF Master), my 4.5/210mm @1.5 meter would give me 40mmDOF on my 4x5 plates. But the results are much more commons!

Attachment 175365

John,

One important thing to add is OOF roll off nature !!!

To have the same framing than in 4x5/210mm if you shot with a 16x20" camera you would be using a 840mm lens.

You may set an aperture in the 840mm to have the same 40mm DOF you mention, in that range the image will be the same, considering format equivalent CoC (circle of confusion).

but the way the image gets more blurred as it goes beyond the dof range should be different.

Sometimes I used an smartphone app to learn how a lens/distance/aperture will roll off in the OOF, see here how it shows the CoC grows :



This is why you see a different OOF nature from what you see from a 4x5, if I'm not mistaken...

PD: as Totias also points...

[tonyowen]

Hi everyone! My mind's stuck on this beautiful and well-known photograph by M. Quinn Jacobson:
Can someone explain me how to achieve such a short dof?

Why not address the question to M. Quinn Jacobson???
To my knowledge he is still alive and functioning.
regards
Tony

[williaty]

John,

One important thing to add is OOF roll off nature !!!

To have the same framing than in 4x5/210mm if you shot with a 16x20" camera you would be using a 840mm lens.

You may set an aperture in the 840mm to have the same 40mm DOF you mention, in that range the image will be the same, considering format equivalent CoC (circle of confusion).

but the way the image gets more blurred as it goes beyond the dof range should be different.

Sometimes I used an smartphone app to learn how a lens/distance/aperture will roll off in the OOF, see here how it shows the CoC grows :



This is why you see a different OOF nature from what you see from a 4x5, if I'm not mistaken...

PD: as Totias also points...

What app is that?

[Pere Casals]

What app is that?

https://play.google.com/store/apps/d...achs.dof&hl=es

you can add new custom cameras of any format, etc

"A compatible version of DoF is also available for Windows computers at:" www.dl-c.com/DoF

[williaty]

https://play.google.com/store/apps/d...achs.dof&hl=es

you can add new custom cameras of any format, etc

"A compatible version of DoF is also available for Windows computers at:" www.dl-c.com/DoF

Anyone know of a similar app for iOS or macOS?

[paulbarden]

Yap! But my trouble is mainly on DOF questions!

The image you're inquiring about is a wet plate collodion photo, either made on glass or metal. Lenses made for the process (dating to the early 1850s, when Wet Plate Collodion was invented) had very specific traits, especially evident in the portrait length lenses, and it was typical that they had very shallow depth of field, as they were meant to be used wide open (they had no apertures, and not until later years did they have slots for waterhouse stops). The lens designs of the 1850s (and for a period afterwards) were of the Petzval design, which did not have a flat focal plane, but was in fact curved. This Petzval curve enhanced the illusion of very limited DOF, and the closer you were to the subject, the more pronounced the effect becomes. This is what you are seeing in Quinn's photo. Its typical of the effect seen when using many (most?) of those early portrait lens designs.

This is one of the mid-1850s Petzval design lenses: a 15" f5 Lerebours et Secretan:

[goamules]

I'm friends with Quinn, shot with him at the Paris Foto Fair, and moderate his website Collodion.com. Why don't you ask him? He's a nice guy, and has several web sites and training youtube vids. But basically a fast lens with wetplate and natural lighting. Using a flash you won't get the deep blacks around the sitter, usually.

Or go to the Collodion website, or one of the facebook sites (he has one there called Wetplate Photographers), and read up on it. Lots of people doing wetplate today, compared to 10 years ago when I began (when there were about 1 in every state, max). Or if someone is interested, I occasionally do wetplate workshops in Tucson.

2010 wetplate demo booth:

[john_vandale_]

Hi guys! So much good information here!

I have to consider focal plane bending on Petzval lens and sharpness drop off with larger formats...

At this moment I only have a 4x5 camera for my wet plates, though with a few lenses.

Which one do you think will do the better job from this point of view?

- Schneider 5.6/240mm
- Industar 4.5/300mm
- An old brass f8/210mm
- Schneider xenotar f2.8/150mm

(I guess the first 5.6/240mm is out of this game...)