DOF for the M8 - the facts

[Sparrow]

I know I'm making a pest of myself but I still claim the larger format cameras have a reduced depth of field. I thought everyone accepted that. In fact one of the things I don't like about point n' shoots is the too broad depth of field. But now I find that actually the DOF has been razor thin.

I don't get it. Why do my eyes seem to lie?

Rex

Your eyes don’t deceive you, perceptual reality is surely the only thing that counts, the vast majority see a print as you do so it’s that that should inform your photography not the technical detail.

 

[Ben Z]

Sorry it still doesn't compute. I take a shot with a 50mm lens at say f/4, focused at 3m. I make 2 prints. Both of them have the same DOF, right? OK, now I get out my scissors and crop one of the prints by 1/3 all around (that's what a 1.5x sensor does). Has the DOF of that print changed? I think not. Only the angle of coverage.

Now, if you compare a print made with a 50mm lens at f/4 and 3m to the same shot made with a 1.5 sensor and a 35mm lens at f/4 anad 3m, the shots will be (approximately) the same in composition but the second shot will have more DOF...because it was made with a 35mm lens.

This is the same issue that always existed between 35mm and 120. An 80mm on medium format gives the exact same DOF as an 80mm on a 35. The difference is it's a telephoto on the 35 and a standard on the medium format, as a result of the 'sensor' (film area) being smaller.

 

[Ben Z]

For the same print size. You have to enlarge what you cropped with your scissors to the original size, then the DOF decreases.

Aha, so then since DOF is an expression of "acceptible unsharpness", the more the image is enlarged the less will be acceptibly sharp? Got it. Makes sense.

 

[jaapv]

I'd be greatful if you could elaborate on your user experience with this lens - 75 lux. Are there differences between the late Canadian versions and the newest German versions since 1998? Thanks for any info.

Steve

I don't know about any German ones, mine is a Canadian., but I imagine the differences are slight, if any, as the specifications are identical as far as I know.I only bought mine a few weeks ago and sent it off to be coded, so I have few examples. These were both at 1.4 as I recall.I tried it in the theatre and was impressed by its flare-free and good rendering (but struggled with the scan):

Umoja


I used it wide open in the forest and detail and subtle colors made the photo's plastic (but you should see it in print, or even better, slide!)

Colours of Green

 

[rvaubel]

Everyone

We all need to agree on the basic fact that large format cameras are more forgiving about focus and depth of field issues and that point and shoots have very critical focus requirements and razor sharp depths of field.

Lets all agree on that and go from there.

Rex

 

[jaapv]

Everyone

We all need to agree on the basic fact that large format cameras are more forgiving about focus and depth of field issues and that point and shoots have very critical focus requirements and razor sharp depths of field.

Lets all agree on that and go from there.

Rex

DOF is in the eye of the beholder....

 

[rvaubel]

DOF is in the eye of the beholder....

Auuuuuughhhh!!!!!!!

Rex

 

[jaapv]

Sorry..... 😀

 

[rvaubel]

Sorry..... 😀

Well, thats it. LET THE CHALLENGE BEGIN!

The REX VAUBEL DOF CONTEST

You need two cameras for this. A larger format and a smaller format, each with a "normal" lens.

Take a head shot of someone at a distance of someone at 6 ft with a background at infinity, with each camera at the same aperture. Use shutter speed to compansate for difference in ISO, if you can't make them the same.

Make identical enlargements. Compare DOF.

I defy anyone to submit a picture showing that the DOF is equal to or greater in the Larger format.

Rex
past foaming, now having seizures:bang:

I'll post my results as soon as I stop flopping around.

 

[rxmd]

You need two cameras for this. A larger format and a smaller format, each with a "normal" lens.

You mean like a 50 on 35mm, an 80 on 6x6, and so on? But then you're comparing different focal lengths. As Anders and Roland have pointed out, this is an entirely different arena.

I'll post my results as soon as I stop flopping around.

OK. Do yourself a favour and try the same thing again with lenses of equal focal lenth on both negative formats. Use the same lens if you can.

Philipp

 

[rvaubel]

You mean like a 50 on 35mm, an 80 on 6x6, and so on? But then you're comparing different focal lengths. As Anders and Roland have pointed out, this is an entirely different arena.

OK. Do yourself a favour and try the same thing again with lenses of equal focal lenth on both negative formats. Use the same lens if you can.

Philipp

Of course I'm talking about different focal lengths for different formats. What I'm saying is that for a given field of view, say a "normal" one (50mm on 35mm, 80 on 6x6), the smaller format is more forgiving than the larger one. I think that is what Roland was wondering. There are so many hundreds of factors that enter into the theoritical discussion that forgetting one of them can lead to incorrect or even opposite conclusions from reality.

What I have been trying to emphasis, belatedly and without much succress, is that my experience has been that smaller formats have greater depth of field and have more, not less, leaway with regards focusing error. I may be wrong but I swear to god when I look at a 1/8'' sensor 5x7" at F3.5 everything from about 3'ft to infinity looks in focus.

Rex
OOOOOMMMMM

 

[rvaubel]

Rex,

you are right: decrease the format size and decrease the focal length in proportion, the DOF will increase.

My original question was because I was wondering, if, with some luck, my CFO at home would approve an M8 purchase, could I focus my 50/1.2, 85/2, etc.
Or, should I buy an RD1 instead (maybe a broken one that took a fall in the past 🙂 )

But then you convinced me in another thread, it doesn't matter so much, with a digital camera one can always delete out of focus shots and try again.

Plus I might wait until you let me try your M8 🙂

Take it easy. Philosophically,

Roland.

Yah, I thought that was what you were getting at. Well let me say that before ms RD had her rude encounter with the pavement, she could focus the Nikkor 85mm F2.0 pretty good. Now by "pretty good" I mean about 30% or so. That's acceptable for my style of shooting, what with digital deleting and all, but still kind of low. I almost bought a VC 75 F2.5, figuring I'd get a lot more "hits" with it. It would also be equivelent to a 105mm F2.5 which would be a pretty cool focal length for the RD1.

I have had real good luck with the Canon 50mm/1.2 Obviously, the 40mm f1.4 and 28mm f1.9 pose no challenge.

So my take on the M8 is that their is a good chance that it should perform as well as any Leica with the same effective rangefinder baseline. In other words, all the Leica lenses, including the 75mm f1.4

However, I never considered the crop factor to possible put additional strains on the focus/baseline/CofC/etc,etc complex. I guess that is the question you were asking which I missed the first time around. From my viewpoint, coming from a smaller sensor(1.5) to larger(1.3) the critical focus requirements become more severe (a little). From your point of view, coming from film, the critical focus requirements may be relaxed.

Or maybe I got it all backwards🙁

I still think that the M8 should do a better overall job of focusing the faster lenses. This is an area that emperical results are going to trump any mental gymnastics that we may enjoy employing. Not that I would disuade you from continueing on in this vein.... I may even join you!!

Rex
Arf, Arf😀

 

[rvaubel]

At least you call it "gymnastics" now 🙂

Cheers,

Roland.

I'm trying to be more refined

Rex

 

[Bob Ross]

Well, thats it. LET THE CHALLENGE BEGIN!

The REX VAUBEL DOF CONTEST

You need two cameras for this. A larger format and a smaller format, each with a "normal" lens.

Take a head shot of someone at a distance of someone at 6 ft with a background at infinity, with each camera at the same aperture. Use shutter speed to compansate for difference in ISO, if you can't make them the same.

Make identical enlargements. Compare DOF.

I defy anyone to submit a picture showing that the DOF is equal to or greater in the Larger format.

Rex
past foaming, now having seizures:bang:

I'll post my results as soon as I stop flopping around.

Rex,
Here are the dials for five format sizes from DOF Master. COCs are for 8" X 10". I did this a few years ago during a similar discussion with a buddy.
Bob

 

[saxshooter]

The physical lens has the same depth of field since it isn't lens that's physically changing, it's the size of the image area - think cropping. The difference is you get a 28mm with the depth of field charecteristics of a 21mm, the 1.33 conversion factor. So the cropped 21mm, 28mm digital, has more inherent depth of field than a 28mm on a film camera.

Yes, I was trying to make this point in another thread regarding using a 14mm lens on a 1.5x digital SLR. You get the DOF characteristics of a 14mm with a cropped field of view which is around 21mm. The lens isn't changing. It's that you're not seeing the entire height and width of what the lens can give you.

 

[rvaubel]

Yes, I was trying to make this point in another thread regarding using a 14mm lens on a 1.5x digital SLR. You get the DOF characteristics of a 14mm with a cropped field of view which is around 21mm. The lens isn't changing. It's that you're not seeing the entire height and width of what the lens can give you.

Not only do you see the DOF characteristic of the lens (cropped of course) but the quality of the bokah and inherent signature of the lens is readily apparent when moving from a full framd film camera to a reduced format digital. Some of the older lenses have quite a personality which comes thru fine in a digital crop camera. This is to reassure film users that there favorites will come through in the digital world.

Rex

 

[rxmd]

Yes, I was trying to make this point in another thread regarding using a 14mm lens on a 1.5x digital SLR. You get the DOF characteristics of a 14mm

Not precisely, it should be more like a 17mm because of the different acceptable circle of confusion, which is where we're back to "Go", metaphorically speaking 😀 :bang: :bang:

Philipp

 

[rvaubel]

Not precisely, it should be more like a 17mm because of the different acceptable circle of confusion, which is where we're back to "Go", metaphorically speaking 😀 :bang: :bang:

Philipp

And I thought my seizures had finally stopped.

Rex

 

[rxmd]

Oh, but that doesn't make that much of a difference in practice. I think Francesco posted a formula in the other thread (here) that on a body with 1.5 crop, a lens with focal length X gets the field of view of a lens with 1.5*X and the DOF of a lens with approximately 1.2*X. That should be fine to work with, you don't have to go into the math.

Philipp