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DOF for the M8 - the facts
Old 09-19-2006   #1
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DOF for the M8 - the facts

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.
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Old 09-19-2006   #2
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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
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Old 09-19-2006   #3
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Quote:
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....
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Old 09-19-2006   #4
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Quote:
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.

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Old 09-19-2006   #5
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Quote:
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.
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Old 09-19-2006   #6
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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.
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Old 09-19-2006   #7
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Quote:
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).

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Old 09-19-2006   #8
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Here is a fairly interesting article (& thread) concerning DOF/Digital:
http://photo.net/learn/optics/dofdigital/
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Old 09-19-2006   #9
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Quote:
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!!
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Old 09-19-2006   #10
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Quote:
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.
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Old 09-19-2006   #11
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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.
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Old 09-19-2006   #12
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Quote:
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,

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Old 09-19-2006   #13
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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.
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Old 09-19-2006   #14
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Quote:
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.
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Old 09-19-2006   #15
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Quote:
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
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Old 09-19-2006   #16
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Quote:
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!
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Old 09-19-2006   #17
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Zoom lens

Zoom lens are so '80s

Quote:
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!!
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Old 09-19-2006   #18
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Quote:
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
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Old 09-19-2006   #19
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Quote:
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
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Old 09-19-2006   #20
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Quote:
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
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Old 09-19-2006   #21
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Quote:
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.
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Old 09-19-2006   #22
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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.
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Old 09-19-2006   #23
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Quote:
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.
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Old 09-19-2006   #24
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Quote:
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!)

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Old 09-19-2006   #25
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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
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Old 09-19-2006   #26
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Quote:
Originally Posted by 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

DOF is in the eye of the beholder....
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Old 09-19-2006   #27
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Quote:
Originally Posted by jaapv
DOF is in the eye of the beholder....

Auuuuuughhhh!!!!!!!

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Old 09-19-2006   #28
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Sorry.....
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Old 09-19-2006   #29
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Unhappy

Quote:
Originally Posted by jaapv
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
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Old 09-19-2006   #30
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Quote:
Originally Posted by rvaubel
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.

Quote:
Originally Posted by rvaubel
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
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Old 09-19-2006   #31
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Quote:
Originally Posted by rxmd
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.

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Old 09-19-2006   #32
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Quote:
Originally Posted by ferider
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
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Old 09-19-2006   #33
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Quote:
Originally Posted by ferider

At least you call it "gymnastics" now

Cheers,

Roland.
I'm trying to be more refined

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Old 09-19-2006   #34
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Quote:
Originally Posted by rvaubel
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

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
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Old 09-19-2006   #35
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Quote:
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.
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.
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Old 09-19-2006   #36
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Quote:
Originally Posted by saxshooter
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
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Old 09-19-2006   #37
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Quote:
Originally Posted by saxshooter
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

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Old 09-19-2006   #38
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Quote:
Originally Posted by rxmd
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

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Old 09-20-2006   #39
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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.

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