Why is the DOF of 4x5 greater than 35mm?

I'm missing something here.. by I thought that the DOF of lenses would be the same regardless of format. However, using a DOF calculator that doesn't appear to be the case..

4x5, 210mm @ f/5.6 at 2.5m gives a DOF of 14.7cm
35mm, 210mm @ f/5.6 at 2.5m gives a DOF of 4.4cm

If that is the case.. why all these complaints about how to have to stop 4x5 down more to get everything in focus.. ?

Infact, it would appear that the 4x5 210mm shot wide open will give backgrounds similar to 135mm @ f/7.1 on 35mm. Thats hardly blury at all from experience.

Hopefully the bokeh on LF lenses will be good.. since alot more of the background is going to be in focus! Will my Sironar-S will be sharp wide open? (doesn't arrive until probably monday).

Daniel.

PS. Try for yourself here;

http://www.dofmaster.com/dofjs.html

The film size is irrelevant. What is relevant is the focal length, the aperture and - this is the important bit - the acceptable circle of confusion.


Steve.

A lens doesn't know what format it's focused on so DOF is the same no matter what. But, as a practical matter, DOF calculators assume you won't be enlarging 4x5 as much as 35mm, and therfore that a greater degree of fuzziness (circle of confusion) is acceptable.

The reason LF generally requires high f-stops (in spite of the above) is because it requires longer focal length lenses to give equivalent fields of view of lenses for smaller formats. While a 28-35mm lens gives a wide view on 35mm film, it takes a 90mm lens to get the same approximate angle on a 4x5 piece of film. And a 90mm lens has less dof for a given f-stop than a 35mm lens, so LFrs generally find themselves shooting at higher f-stops.

Theat is because on a larger format you can have a larger acceptable circle of confusion.
Here are a couple of links to give you further understanding on how DoF and CoC varies on different format, even when the focal length of the lens is the same. Simply put; it's a matter of enlargement.

http://www.cambridgeincolour.com/tutorials/depth-of-field.htm
http://en.wikipedia.org/wiki/Depth_of_field
http://www.cs.mtu.edu/~shene/DigiCam/User-Guide/950/depth-of-field.html

formerly confused too -- MW

Ok... so if I take a portrait at 2.5 metres wide open.. I'll be able to blur the background a bit? I have a favorite spot on my balcony with a tree behind which covers the sun pefectly at sunset.. and I'm longing to re-do this shot with some Polaroid 55 and find out about this tonality you guys talk about.

Only want to print 10x10



Can anyone post me some examples of their wide open portraits? Thanks!

Daniel.

snaggs said:

Infact, it would appear that the 4x5 210mm shot wide open will give backgrounds similar to 135mm @ f/7.1 on 35mm. Thats hardly blury at all from experience.

Hopefully the bokeh on LF lenses will be good.. since alot more of the background is going to be in focus! Will my Sironar-S will be sharp wide open? (doesn't arrive until probably monday).

Click to expand...

Your field of view with a 210 mm lens on 4x5 is much greater than that of a 135 on 35mm, so you are not comparing equivalent lenses. If you plan to crop your 35mm image to make an 8x10 print (for example), an equivalent lens for a 4x5 to your 135 would be about 550mm. By the same token, your 210mm 4x5 lens is about equivalent to a 52mm lens on 35.

So, in reply to your question about the portrait at 2.5 meters, your 210 lens on 4x5 will give you a field of about 1.15m x 1.45m. You don't say what lens you shot your example with, but it looks to be considerably longer than a 50. Obviously, to cover the same field as your example, you will have to move closer with the 4x5.

Daniel,

There's no way to answer the question without knowing what lens you'll be using, how far you can open it, how far away the trees are relative to the subject, etc... For this specific shot, DOF calculators, or even our input, will be of limited use. You're best off just setting up the shot and maneuvering around until the ground glass gives you the look you want. If you're happy with what the ground glass shows, you'll be happy with a 10x10 print from it.

My guess is that any lens in the 150mm range or above will give you the look you want, if shot wide open.

The tree's are about 1-2 metres behind the subject. The shot there was done with a 105mm f/2 DC Nikkor.

Good point about the field of view.. I'll have to get closer for the same crop of the DOF will change.

I'm just a bit annoyed since I was told a 210mm was about the same FOV as a 70mm and that DOF on 4x5 was much less than MF, let alone 35mm. So I'm just worried I've bought a new lens with my Tachihara which I'll be unhappy with before its even out of the box.

I have a Rodenstock 210mm Sironar-S f/5.6 arriving with my Tachihara any day now.

Daniel.

A standard lens on 5x4" is about 160mm (diagonal of the film format). The same for 35mm film is 43mm. This gives a ratio of 160:43 or about 3.72:1.

Therefore, your 210mm lens is equivalent to 210/3.72 = 56mm so just a bit longer than a standard lens but not quite the 70mm you were quoted. For that you would need a lens around 70 x 3.72 = 260mm.

The DOF will be less on 5x4" so I think you will probably be happy with the lens for the use you have planned.

Steve.

Don't worry. You will NOT be disapointed with that lens. Just frame the shot till it looks good to you. You might be close enough to need a little bellows correction but so what. I see absolutly no problem with you getting that on 4x5.

The thought process I try to take myself through goes something like this:

1) Choose a camera position that results in the right viewpoint and perspective (e.g. being really close accentuates depth, while being farther away flattens features);

2) Choose a lens that allows you to fill the frame with the subject;

3) Choose an f/stop that gives you the depth of field you need.

If you have movements available, they should be taken into account when deciding on points 1) and 3).

Matt

In the last month or two I posted a series of postings dealing with this. Please do a search on DOF and there you will find a number of links.

The bottom line [to ruin the plot] is that DOF depends on the circle on confusion, the size of the enlargement and image size on the focal plane.

Sorry about the bad news. Physics can be a bitch sometimes.

Steve

Steve Smith said:

A standard lens on 5x4" is about 160mm (diagonal of the film format). The same for 35mm film is 43mm. This gives a ratio of 160:43 or about 3.72:1.

Therefore, your 210mm lens is equivalent to 210/3.72 = 56mm so just a bit longer than a standard lens but not quite the 70mm you were quoted. For that you would need a lens around 70 x 3.72 = 260mm.

Click to expand...

I calculate focal length equivalents differently (rightly or wrongly), because the aspect ratio is different. Thus, the correction will be different if your end product has a 4x5 or a 4x6 aspect ratio.

A 35mm image, whose native aspect ratio will produce a 4x6 image, will need 1/6 cropped in order to produce the same aspect ratio as a 4x5, 8x10, etc. So to make an 8x10 print from a 35mm frame, you need to make an 8x12 and crop. The correction factor is actually 4.2 for this scenario (4 inches = 101.6mm, divided by 24mm of the 35mm frame). So, for an output that is 8x10, 16x20, etc, a 210mm lens on 4x5 would correspond to a 50mm lens on 35mm, and a 35mm lens on APS.

Of course it's a different story if your output is 4x6 ratio, because then you'd need to crop the 4x5 frame down to 3.3x5, making your conversion factor 3.5 instead.

I'm really interested in square format and the polaroid 55 look which you can't really crop if you want to keep the funky edge.

Btw everyone, I woke up this morning hoping to see some inspiring portraits that you'd all done. Come on, dont be shy!

Show me some portraits done using a 210mm lens!

Daniel.

I like the 210 for 'environmental' portraits, and 300 for tighter portraits. The first is a 210mm square shot of my brother's family, and the second is a 300mm 'portrait' of a statue.

snaggs said:

Btw everyone, I woke up this morning hoping to see some inspiring portraits that you'd all done. Come on, dont be shy!

Show me some portraits done using a 210mm lens!

Daniel.

Click to expand...

I made portraits of my niece when she was a baby using my 210mm lens, but I'm afraid I can't show them because I own neither a flatbed nor a 4x5 scanner. But I can tell you that all the time I owned the 210, I wished for a longer lens for portraits. Later I sold it and bought a 240mm, which was better, and now I have a 270, which is much better!

As drpablo pointed out, to compare lenses of different formats, you need to somehow equate the format proportions first. That's why I specified in my post that my comparison assumed that you made 8x10 prints from both formats.

Here's how to compare lenses. Divide the length and width of the film format by the focal length of the lens; then divide the length and width of the other format by the same factors, and you get the equivalent lens focal length in the second format.

Example: a 4x5 negative measures about 97x120mm. For a 210 lens, 97/210=.46; 120/210=.57.
A 35mm negative measures 24x36mm, but to get an 8x10 proportion, you have to crop it to 24x30mm. So 24/.46=52mm; 30/.57=52.5mm (the differences are due to rounding).

Example 2, if you want to compare full-frame 35mm to an equivalent proportion on a 4x5 negative:
A 35mm negative, being 24x36mm, is in the ratio of 2:3; a 4x5 negative cropped to the same proportion would give a useale area of 80x120mm. So now using this size for the calculations for a 210mm lens: 80/210=.38; 120/210=.57.
A 35mm equivalent lens would be 24/.38=63mm, 36/.57=63mm. This is closer to the 70mm figure you were told, and perhaps explains the discrepancy.

Hope this helps.

I think your right.. I really need something around 400mm and fast. Nikon and Canon and every man and his dog can make a 400mm f/2.8. So why can't our german elves make us at least a 400mm f/4 telephoto ?

Daniel.

Daniel, if you go to my photographs by clicking on my name and checking out my gallery, you will see two contact 4x5 prints which I scanned and put in specifically for your benefit.

The two pictures were taken about 5 minutes apart and all I did was move the camera forward to further blur the background as I had to focus closer. This meant that I had more bellows extension and I ended up adding a stop by using a different shutter speed.

In each case the lens used is a near 50 year old 215mm f/6.3 Caltar used at f/22 the camera used is a very tired but very workable Calumet monorail.

I have made a 12x16" cropped enlargement of the sheet where you see the chair, beautiful print, needed a bit of work on the B/ground and the shirt. No spotting required, not one.

The other sheet I will be working on this weekend, with another 12x16" cropped print. There are no marks on this negative either, so I shouldn't require spotting for this as well. FWIW, I usually take about 5 minutes minimum to close to 10 minutes ensuring my negatives are as clean as a whistle before I start, it's doable.

I took these pictures two Saturdays ago, so they are recent and relevant.

I think you need to use your camera, fiddle a bit, use your camera, fiddle some more and finally, use your camera.

You will be quite surprised at how easily things will start to fall in place once you start to use your camera.

I only have one lens, it's amazing what you can do with one lens. I do in the future intend to acquire another lens, but I'm still fiddling.

Mick.

PS:- welcome to the forum and good to see someone else in this country.

Thanks Mick, I think I will just work with the 210mm and learn to do a different style. It was my intention to treat this camera and lens as a a working unit and eschew gearitus.

Thanks for taking the time to do this.. Now, you mentioned spending alot of time making sure the negatives were clean. What are all the white flecks on this image?

(there was a url link here which no longer exists)

or is tha just the scanner?

Daniel.

snaggs said:

I think your right.. I really need something around 400mm and fast. Nikon and Canon and every man and his dog can make a 400mm f/2.8. So why can't our german elves make us at least a 400mm f/4 telephoto ?

Daniel.

Click to expand...

I'm sure they could! But to make one with coverage for 4x5 plus movements would probably cost about as much as a new Lexus.

Daniel, the print with the spots on is the first print I scanned, I noticed dust spots so I just wiped the scanner with a rag for the second scan.

The negatives are safe in the darkroom and only see the inside of an enlarger.

The prints are my contact prints of which I print 4 to each 8x10" sheet of paper. I took 8 sheets that day, four with the chair visible and 4 close up. In each case I was able to get a very good pictorial content neg, for enlarging.

Mick.

snaggs said:

Nikon and Canon and every man and his dog can make a 400mm f/2.8. So why can't our german elves make us at least a 400mm f/4 telephoto ?

Click to expand...

You wouldn't need a 400 f/4 most of the time. For small format photography, when you're using a 400mm lens (which is an extreme telephoto), you need that speed for handholding, birds, sports, etc. With a view camera odds are you're not going to be freezing birds much of the time, and you'll be using it on a tripod. The major advantage to f/4 would be a brighter image on the ground glass, but f/5.6 is plenty bright, and even at f/8 and f/11 the image is pretty clear.

" Originally Posted by snaggs View Post
Nikon and Canon and every man and his dog can make a 400mm f/2.8. So why can't our german elves make us at least a 400mm f/4 telephoto ?"

Remember that Nikon and Canon only have to cover a postage stamp.
A 400mm f2.8 Large-Format lens is not practical, here are some other options:

Wollensak Tele-Optar/Raptar 15" f5.6
Schneider Kreuznach Tele-Xenar 360mm F5.5
Schneider Kreuznach Tele-Arton 360mm f5.5
kodak Commercial Ektar 14" f6.3
Kodak Aero-Ektar 12" f3.5

These are all big, heavy lenses. The heaviest being the Aero-Ektar which wheis about 10 pounds. The first 4 can all be mounted in leaf shutters, allthough the top speed on these shutters is limited so in bright sunlight you might need to stop down considerably. I have a Wolley 15" tele and its too much for my Zone Vi. But its just purrfect on my Graflex SLR.

If you decide you want something more practical, you have many options ranging from modern to classic. Just take into account that shooting LF is very different than 35mm.

and for some good examlpes of photos taken wide open with LF lenses, look here:
http://www.largeformatphotography.info/forum/showthread.php?t=22286

Thanks all..Australian dollar has just jumped.. I think its time for one more lens from Badger.. what is the best portrait lens for 4x5? I thinking something around 400mm.

Daniel.