DOF for the M8 - the facts

[jaapv]

What are we talking about? A short list (I may add later). All at 3 m distance.

135-2.8
08 cm film
06 cm M8
05 cm RD1

90-2.0
13 cm film
10 cm M8
09 cm RD1

90-2.8
18 cm film
14 cm M8
12 cm RD1

75 - 1.4
13 cm film
10 cm M8
9 cm RD1

75-2.0
27 cm film
20 cm M8
18 cm RD1

50-1.0
21 cm film
16 cm M8
14 cm RD1

50 -1.4
30 cm film
23 cm M8
20 cm RD1

50-2.0
43 cm film
33 cm M8
28 cm RD1

35-1.4
62 cm film
48 cm M8
41 CM RD1

35-2.0
89 cm film
60 cm M8
59 cm RD1

24-2.8
326 mm film
227 mm M8
192 mm RD1

I used DofMaster, calculated the M8 at 0.023 mm and the film at 0.03 mm.
Unless I have been clicking very stupidly,(not impossible at all) or DofMaster is totally out (rather more unlikely), the DOF on the M8 will be more shallow than film at the same focal length, not too much out when "jumping" one length.

[rxmd]

The jump from a 75/1.4 on film to a 50/1.4 on the M8 could be problematic, since you buy a 75/1.4 for the DOF. Some people will have to buy Noctiluxes.

Philipp

[jaapv]

Originally Posted by rxmd

The jump from a 75/1.4 on film to a 50/1.4 on the M8 could be problematic, since you buy a 75/1.4 for the DOF. Some people will have to buy Noctiluxes.

Philipp

Or step 50 cm back and take a 90/2.0....

[rxmd]

Originally Posted by jaapv

Or step 50 cm back and take a 90/2.0....

But then one could have done that with the film M just as well (slight perspective differences notwithstanding). Nevertheless, people choose to blow 3100 EUR on a Summilux 75.

Philipp

[jaapv]

Originally Posted by rxmd

But then one could have done that with the film M just as well (slight perspective differences notwithstanding). Nevertheless, people choose to blow 3100 EUR on a Summilux 75.

Philipp

True- for some- I bought mine used - quite considerably less but not so much for the shallow DOF as for the character of the lens.

[Ben Z]

It doesn't seem correct that a lens would have more or less DOF at the same distance just because the periphery of the image is cropped. Where the DOF difference works in is that to frame the same shot with the same focal length on a 1.33x camera as a FF camera means standing farther back from the subject, and DOF increases with subject distance.

[rxmd]

It doesn't seem correct that a lens would have more or less DOF at the same distance just because the periphery of the image is cropped.

But that's exactly what it does, because you have to enlarge the frame more to get the same image size.

Jaap & I have been discussing this to death today in this thread (which is why he thought of posting this list, I think).

Philipp

[plummerl]

Here is a fairly interesting article (& thread) concerning DOF/Digital:
http://photo.net/learn/optics/dofdigital/

[jaapv]

Originally Posted by Ben Z

It doesn't seem correct that a lens would have more or less DOF at the same distance just because the periphery of the image is cropped. Where the DOF difference works in is that to frame the same shot with the same focal length on a 1.33x camera as a FF camera means standing farther back from the subject, and DOF increases with subject distance.

All DOF figures in my table are at 3 m distance.Comparing would be rather difficult otherwise, as one would drown in a sea of numbers if I had to work it out at various distances. Besides, I'm lazy . I want to shoot sitting in my armchair using a ZOOM lens!!

[jaapv]

Originally Posted by rxmd

Jaap & I have been discussing this to death today in this thread (which is why he thought of posting this list, I think).

Philipp

I was planning this earlier, as there was some full-frame flak a few days ago, but that thread certanly made me add the figures for the RD1.

[ffttklackdedeng]

Jaap,

you didn't take into account the 'you'll take another lens because of crop factor' factor, or did you? As far as I understand you calculated smaller CoC because of the bigger enlargement factor caused by the sensor crop factor.



What I mean is: a picture made with film and a 50mm lens at f2 compared to one made with the RD-1 with a 33mm lens at f2.

[AndersG]

Originally Posted by rxmd

But that's exactly what it does, because you have to enlarge the frame more to get the same image size.

It is indeed so. Here is an example I once prepared to have handy for these kinds of discussions (they sure seem to occur again and again.. )

These two images were taken with the same lens, at the same aperture and the same distance, but with differently sized sensors. The images have then been enlarged to the same display size. Is the DOF the same in both?

[EDIT]
Of course, if we want the same framing the game is different, we would have to change the focal length and/or the subject distance and these changes will also affect the DOF. (Indeed, they will cause a larger increase in DOF for the smaller format than the decrease caused by the extra magnification needed.)
[/EDIT]

Cheers,

Anders

[thurows]

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.

[jaapv]

Originally Posted by ffttklackdedeng

Jaap,

you didn't take into account the 'you'll take another lens because of crop factor' factor, or did you? As far as I understand you calculated smaller CoC because of the bigger enlargement factor caused by the sensor crop factor.



What I mean is: a picture made with film and a 50mm lens at f2 compared to one made with the RD-1 with a 33mm lens at f2.

The lens choice according to the FOV one wishes to have is your own, you can read the relevant DOF in the list.Focal length does not influence the accepted COC, that is fixed according to the format of the film/sensor.- a COC for a 1.33 sensor is 0.023 according to general agreement,for a 1.5 0.02, a 4/3 sensor 0.015, etc. DofMaster will do that automatically for you if you choose your camera from the list.

PS. A different format sensor/film does not change the focal length of the lens - that is a characteristic of the lens - not the camera.

[newyorkone]

Originally Posted by jaapv

True- for some- I bought mine used - quite considerably less but not so much for the shallow DOF as for the character of the lens.

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

[newyorkone]

Originally Posted by thurows

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.

I've never quite understood what the fuss was all about but this single post has cleared things up for me. Thanks!

[ampguy]

Zoom lens are so '80s

Originally Posted by jaapv

All DOF figures in my table are at 3 m distance.Comparing would be rather difficult otherwise, as one would drown in a sea of numbers if I had to work it out at various distances. Besides, I'm lazy . I want to shoot sitting in my armchair using a ZOOM lens!!

[AndersG]

Originally Posted by ferider

I am still convinced that in addition to the more shallow DOF, any RF error gets amplified by the crop factor as well. Will make focusing shallow DOF lenses even harder.

Yes, for a given lens that is correct, since the cropped image will need to be enlarged more and thus shrinking the perceived depth of field and making any fokus error more visible. However, at the same time you'll get a narrower angle of view.

If you instead change to a shorter lens or move back to get the same framing as in the full frame case, the depth of field at the same aperture will be greater and thus the focusing less critical.

Cheers,

Anders

[rvaubel]

Originally Posted by ferider

Thanks for posting this, Jaap.

I am still convinced that in addition to the more shallow DOF, any RF error gets amplified by the crop factor as well. Will make focusing shallow DOF lenses even harder.

Roland.

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

[AndersG]

Originally Posted by rvaubel

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?

Your eyes don't lie - it is just that you compare the two formats using the same angle of view and subject distance but then by necessity with different focal length lenses. This is also a perfectly valid comparison.

So, in short: if you'll use the same set of angle of views on your new smaller format camera - no worries! DOF at the same apertures will be greater.

If OTOH you'll use the same set of lenses then you might need to worry since a lens that was hard to focus accurately on the larger format might be next to impossible on the smaller format.

Cheers,

Anders

[Sparrow]

Originally Posted by rvaubel

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]

Originally Posted by ferider

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]

Originally Posted by newyorkone

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