Optimum aparture for close-up portraits in 4x5

[robrover]

I returned to film about 18 months ago. I was attracted to the amazing detail of 4x5 and have been teaching myself how to take landscape photos. I started with an MPP Micro Technical Mk8 and have recently acquired a very lightweight Intrepid Camera Company 4x5.
I have started taking outdoor close-up, head and shoulders, portraits of long suffering family members and close friends. I am using a Rodenstock Apo-Ronar 1:9, 240mm for portraits. With this lens I have worked out that the optimum focus distance to the subject is about 1.5m. At this distance the subject's head and shoulders fit the frame in a balanced way in the portrait orientation (long side up) of the film.
I want the background to be out of focus so as not to distract from the subject. According to a DoF table I found on the internet, the depth of field for this lens at 1.5m is about 21cm at f32. I have estimated that this drops to about 7cm when the lens is fully opened at f9. The lens will stop down to f64 but I understand that it is best to avoid extreme apertures because they increase diffraction blur. With smaller format cameras I know that the advice is to open the lens up to increase the bokeh. Am I correct in assuming that providing there is some space (perhaps 1m?) behind the subject the background will be out of focus with any aperture with this lens? What would the optimum aperture be for this lens for this type in this situation? Am I right in thinking that f22 or f32 will be a good compromise (providing of course that I can persuade subjects to sit still long enough for a slightly longer exposure)?

 

[Eric Rose]

If you are doing portraits you may, but not necessarily, run into bellows factor issues. Make sure you take this into consideration when doing your exposure calculations. Since you can preview your image on the ground glass just dial in the DOF you are looking for. I suggest using 400 ISO film so you can minimize movement.

Don't get all wound up on bokeh. If you have an arresting portrait no one will notice (except other photographers) whether your bokeh is "good" or "bad". However some lenses are quite awful in OOF areas so again just look at your ground glass and check it out. You may find you might need to change lenses, or maybe not.

Your initial investigations are taking you in the right direction. I suggest you use a melon the size of a human head and do some experimenting before going "live".

Most of the fun is in learning how to get what you have in your minds eye. Good luck!

 

[John Koehrer]

^^And as Edward Weston have the melon as a tasty reward.

Most of peppers ended their lives on the end of a fork.

 

[robrover]

Hi Eric, Thanks for the advice, much appreciated. When you write "bellows factor issues" do you mean reaching the end of the bellows extension on the camera?

Melons have a certain an attraction. They don't fidget and keep asking if we are done yet...

 

[Dan Fromm]

PMFJI. Rob, as the lens is focused closer than infinity the effective aperture falls. For most purposed the effect can safely be neglected, but it can be important when working close up.

You said in post #1 above that you want to use a 240 Apo Ronar at 1.5m. This means you're working at a magnification of roughly 1:6, i.e., the image on film is roughly 1/6 the size of this subject. At this magnification the effect is small and you can ignore it safely.

 

[tedr1]

The aperture scales are accurate when the lens is focused at infinity. When the lens is focused at 1.5m that requires the bellows to be extended, and this causes the brightness of the image on the film (and ground glass) to be dimmer. In order to compensate the exposure is increased and the increase is called the bellows extension factor. Depending on the lens and the extension the correction factor may be in the order of one half to one stop more exposure. I am pretty sure a text book on large format will have a formula for bellows extension factor calculation and there is probably something online also, pretty simple maths.

 

[Terry Breedlove]

Maybe with a patient model you can sit down and move him or her until you get the desired look in the view finder. Measure that distance and lens combination for future use. Take shot and see what you have.

 

[wiltw]

Most DOF calculators assume poor human eyesight, same as 'manufacturer standard' assumption in DOF Scales engraved on 135 format or medium format lenses!
20/20 vision human visual acuity indicates that 240mm lens on 4x5 camera with aperture at f/8 has 20/20 vision DOF zone of 2.1cm (on 8x10" print viewed from 10")

At f/16, 20/20 DOF is 4.2cm
At f/32, 20/20 DOF is 8.4cm

 

[hsandler]

I think the problem with very tight portraits in large format is that the depth of field is so small that there is a risk of the subject moving between the time you focus and the time you get the film in place and the dark slide out, such that the eyes go out of focus. I would suggest backing up a bit, stopping down to f16 at least, and cropping. A general issue is that portraits are often less flattering when shot from only 1.5 m away--noses toward the camera look bigger for example because that inch or so closer to the camera becomes a significant fraction of the distance.

 

[robrover]

Thanks to everyone for their advice. Lots for me to learn. To that end I did a test shoot yesterday. I rigged up a simple test target with mini USAF type charts stuck to a board at 5cm intervals from the focus point. The aim was to shoot at 1.5m at different f stops to see how the focus was actually affected and how the bokeh looked.
I took 4 shots with the 240mm lens at f9, f16, f32 and f45. Here are cropped scans of the results. I would probably choose f16 (or perhaps f22 which I didn't test) for a compromise between DoF and sufficient bokeh. Top left f9, top right f16, bottom left f32 and bottom right f45.

 

[Dan Fromm]

That's nice. What does it have to do with a head-and-shoulders or a head along portrait?

 

[adelorenzo]

I shoot portraits with f/5.6 lenses, I normally stop down to f/8. Even on my 270mm Nikkor this works fine.

Get the eyes in focus, the rest of it will sort itself out IMHO.

 

[MultiFormat Shooter]

Even on my 270mm Nikkor this works fine.

Will this lens cover a 4"x5" piece of film or do you use it on a 6x9cm camera? There was a 270 mm Nikkor that I looked at, briefly, but is was listed as only having enough coverage for a 6x9cm image.

 

[M Carter]

Nice job with the testing - as I read your original post I was going to reply "just test it yourself". Best way to suss out diffraction for any lens on any format. Your DOF test strategy made plenty of sense, too.

For so many questions on photo forums, the best answer is "do a test and get back to us"! Often testing shows you things you weren't even looking for, too.

 

[Dan Fromm]

Are you thinking of the 270/6.3 Nikkor-T, image circle 114 mm @ f/6.3, 160 mm @ f/22? A telephoto lens with the expected small coverage.

I don't believe there's any other 270 Nikkor. f/5.6 Nikkor-Ws run 240, 300. adelorenzo may have misspoken.

 

[Alan Barton]

Couple of suggestions - one try using a Kodak Portrait lens - pretty sharp when you want it to be, at wider apertures looks more soft focus. May just be the feel you're looking for. Also darker backgrounds, especially outside, a decent distance from the "victim" always look better than backgrounds with with a lot of distracting highlights. Best of luck!

 

[adelorenzo]

Will this lens cover a 4"x5" piece of film or do you use it on a 6x9cm camera? There was a 270 mm Nikkor that I looked at, briefly, but is was listed as only having enough coverage for a 6x9cm image.

Mine is the T series lens and it seems to cover well. According to the specs at f/22 it just barely covers 4x5 format at infinity but IME only if I fully max out the rise on my Super Graphic do I get some vignetting in the corners.

Coverage is far less wide open but at portrait distances it does not seem to be an issue.

 

[MultiFormat Shooter]

Are you thinking of the 270/6.3 Nikkor-T, image circle 114 mm @ f/6.3, 160 mm @ f/22? A telephoto lens with the expected small coverage.

Yes, that's the one I was thinking of.

Mine is the T series lens and it seems to cover well....Coverage is far less wide open but at portrait distances it does not seem to be an issue.

For the types of shooting for which I would use a lens of that general focal length, I would need it to cover 4"x5" at infinity, wide-open, to make sure I have plenty of "wiggle room" with respect to aperture choice and subject distance.

 

[robrover]

That's nice. What does it have to do with a head-and-shoulders or a head along portrait?

Dan, I imagined focusing on a subject's eyes at the zero position on the test charts. I wanted to find what the out of focus areas actually looked like, especially the background. Rob

 

[Jarin Blaschke]

Thanks to everyone for their advice. Lots for me to learn. To that end I did a test shoot yesterday. I rigged up a simple test target with mini USAF type charts stuck to a board at 5cm intervals from the focus point. The aim was to shoot at 1.5m at different f stops to see how the focus was actually affected and how the bokeh looked.
I took 4 shots with the 240mm lens at f9, f16, f32 and f45. Here are cropped scans of the results. I would probably choose f16 (or perhaps f22 which I didn't test) for a compromise between DoF and sufficient bokeh. Top left f9, top right f16, bottom left f32 and bottom right f45.
View attachment 178157 View attachment 178158 View attachment 178159 View attachment 178160 View attachment 178161 View attachment 178162

You may want to have someone check your ground glass depth - your -5 is sharper than your 0.

 

[robrover]

Jarin, you are right. It may be a focusing error on my part. Are you saying that the GG might be in a different plane to the film when the holder is inserted? Not sure how to measure this.

 

[robrover]

Jarin, here is a crop from the f9 photo where the difference is most noticeable.

 

[hsandler]

I don't know the Intrepid at all, but a common source of small focus errors is the ground glass being inserted facing the wrong way. It's normally with the ground side facing towards the lens, and if there is a Fresnel sheet, and the glass holder was designed to hold a Fresnel sheet, the sheet goes on the lens side of the ground glass with the inscribed side facing the ground glass. If the glass holder was not designed to hold a Fresnel sheet, then the Fresnel goes between the user and the ground glass with the inscribed side against the ground glass.

 

[ic-racer]

If you have a dark cloth, you could probably watch the ground glass as you stop down to get the effect you desire.

 

[robrover]

Jarin's accurate observation has caused some "consternation in the ranks"! I have just had a proper look at the GG screen and plywood holder on the Intrepid and compared it to the alloy one on my MPP Micro-Technical Mk8. Both have a depth of 5mm from the face that mounts onto the back of the camera to the lens facing surface of the GG. There is a tiny variation, probably less than +/-0.2mm between the four sides of the mount. In truth, I can't measure this with consistent accuracy using the simple depth gauge on my mechanical vernier caliper gauge. The Intrepid GG holder is CNC machined from plywood so I wouldn't expect it to be able to hold a tolerance of less than +/-0.2mm. Obviously the guys from Intrepid will know better. I did find that the GG was a little bit loose in holder so I have tightened the retaining clamps. So unless this slight looseness of the GG was the cause I don't think the camera was at fault and I probably didn't focus accurately enough. I might repeat this photo test to check. At the end of the day the Intrepid is an inexpensive lightweight camera. It is early days but if I can get good consistently pictures with it I will make it my normal 4x5 for back-packing. The MPP is obviously more robust and stable but is very heavy in comparison.