Messages

31

Canon General / Re: "Old Lenses" and "Digital Camera Compatibility"?

« on: September 15, 2011, 12:25:37 AM »

Hi, b,

These include the so-called quasi-telecentric designs, in which the exit pupil of the lens is quite far forward.

I love it when you stop by Doug. Not only do you always drop some serious knowledge; you're the only one that consistently breaks out terms I have to google. 

Well, thanks.

Best regards,

Doug

32

Canon General / Re: "Old Lenses" and "Digital Camera Compatibility"?

« on: September 14, 2011, 08:19:18 AM »

Hi, d,

Are "old lenses" that predate digital cameras different in some way?

One issue relates to angle of incidence - the angle at which rays strike the sensor.

Film responds to oblique rays (those that do not strike at right angles) proportionately to the cosine of the angle of incidence (which is measured with respect to arrival at right angles). This is one ingredient in the fall-off of effective exposure for off-axis parts of the scene (natural vignetting), as well as a loss of effective exposure even for on-axis scene points in the case of a large-aperture lens..

With a typical digital sensor, the fall-off in response may be faster than as the cosine of the angle, thus exacerbating the fall-off in effective exposure. The problem is most pronounced in wide-angle lenses.

To mitigate this, in lenses intended to be usable in digital cameras, design schemes are often used than decrease the maximum obliquity of the rays. These include the so-called quasi-telecentric designs, in which the exit pupil of the lens is quite far forward.

The bottom line is that wide-angle lenses (in particular) not specially designed for use with digital cameras may exhibit more off-axis fall-off, and more "shortfall" of effective exposure at large apertures, than we might wish.

Another issue is that digital cameras may be more susceptible to internal reflections caused by rays bouncing between the sensor and various lens surfaces. For that reason, in lenses specifically intended to be usable with digital cameras, special attention may be given to anti-reflective coating and the curvature of critical lens surfaces.

For that reason, lenses not having that design attention, when used on a digital camera, may exhibit more loss of contrast (through "flare") or even overt "sun dogs" than when used on a film camera.

Best regards,

Doug

33

EOS Bodies / Re: Art Wolfe Confirms the 1Ds Mark IV?

« on: September 13, 2011, 02:02:41 PM »

Hi, L,

A typo vs. what?

A mental slip;an accidental jump between two similar thoughts.

The other thought being what?

Best regards,

Doug

34

EOS Bodies / Re: Art Wolfe Confirms the 1Ds Mark IV?

« on: September 13, 2011, 11:02:11 AM »

HI, CR,

Art would be a guy that would have an advanced look, I’m just not sure it wasn’t a typo.

A typo vs. what?

Best regards,

Doug

35

Canon General / Re: Why does it say PowerShot SX30 IS under my name here in Canonrumors

« on: August 22, 2011, 05:53:19 PM »

Hi, H,

I have never owned a camera like this in my life. I have a Eos 1 D mk III and not a PowerShot SX30 IS. 

That's a membership "rank", like "Chevy", "Buick", "BMW", and "Ferrari".

I know, it's just too cutesy!

Best regards,

Doug

36

United Kingdom & Ireland / Re: Compatibility question

« on: August 16, 2011, 08:48:42 AM »

Hi, Casper,

Hi,
I own a Canon 450D at present but am waiting for the next release of the 5D.
In the meantime I'd like to buy a lens which would hopefully fit both. Is the Canon EF 85mm f/1.2L II USM compatible with both cameras?

Absolutely.

Note that when the lens is used on an EOS 5D, because of its larger sensor size than that of the 450D, the field of view will be greater.

Best regards,

Doug

37

Lenses / Re: Which is the best "normal" prime for a Crop Camera?

« on: August 13, 2011, 11:31:49 PM »

Hi, p,

I have a 7D and want to get a fast prime lens that would be close to the equivalent of a 50mm on a FF camera.

Well, the lens that, on an EOS 7D, would give the same field of view as would a 50 mm lens on a full-frame 35-mm camera would have a focal length of about 31 mm.

But you might mean something else by "would be close to equivalent".

Best regards,

Doug

38

Landscape / Re: Post Your Best Landscapes

« on: August 09, 2011, 03:03:04 PM »

Hi, K,

Just started doing HDR's .... Here is one I did recently

Very nice image.

What dynamic range does it have?

Thanks.

Best regards,

Doug

39

EOS Bodies / Re: 1Ds Mark IV Dimensions Outed?

« on: July 30, 2011, 05:15:04 PM »

That entry does not now seem to be in that table at Gigapan.

Best regards,

Doug

40

Canon General / Re: Canon 3 Layer Sensor (Foveon Type?) Patent

« on: July 07, 2011, 12:38:21 PM »

I wonder why they (Sgima) call it (SD1) 46Mp camera

Because it is a larger number.

Best regards,

Doug

41

EOS Bodies / Re: 36x36 mm cmos sensor

« on: June 10, 2011, 11:28:02 PM »

anybody sees any chance for a Canon EOS cmos-sensor that says goodbye to the 24x36mm "full-frame" limitation and actually provides the maximum format that the EOS optical system allows?

From my understanding, a 36x36 mm square format would be handled by any EF-lense without any issues. The EOS optical system is a circle, right - not an ellipse.

The largest square format that the current EF lens image circle (when an actual circle) could handle is 30.6 x 30.6 mm.

In some of the lenses, the image boundary is not quite a circle. Then a slightly smaller square format is all that could be handled.

Best regards,

Doug

42

Lenses / Re: Why did Canon make EF-S lenses

« on: June 08, 2011, 10:43:28 AM »

Hi, H,

Why did Canon make EF-S lenses

The object of the EF-S lens series is twofold:

• If the lens is not intended to be used on "full-frame 35-mm size" sensor cameras, but rather those with a smaller sensor size, it can have a smaller image circle, and this makes it easier to design for a certain set of optical properties with a certain optical performance.

• If the lens is not intended to be used "full-frame 35-mm size" sensor cameras, but rather those with a smaller sensor size (and thus a smaller reflex mirror, assuming an SLR arrangement), then the lens can have a smaller "back focus" (the physical distance from the rearmost point on the lens to the focal plane), which simplifies the design of lenses with smaller focal lengths.

Overall, then, we might expect that the objective is to allow the design of lenses for use only on "smaller-format" cameras that are less costly, smaller, and/or lighter, for given optical properties and optical performance, than if they were designed to be used on all cameras of the genre, including those with a full-frame 35-mm sensor size.

Note that the focal length quoted for EF-S lenses is (nominally) the "actual" focal length of the lens (the only focal length it has). It is an optical property of the lens, and does not presuppose its use in any particular format size camera . The lens has that property on any camera it will fit, or when in its carton.

The stating of the "full-frame 35-mm equivalent focal length" for a lens as it will be used on a camera of some particular format size, other than "full-frame 35-mm", is intended to allow the real property of interest, the field of view of the lens when used on that camera, to be expressed in a familiar, traditional form which can be compared to work with a full-frame 35-mm format camera. It is not an actual focal length of the lens under any circumstances.

Best regards,

Doug

43

EOS Bodies / Re: Very few EOS 1 bodies sold - wonder why!!

« on: June 01, 2011, 06:54:09 PM »

In the latest rumour it was mentioned that canon sell hardly any EOS 1 bodies relative to the 5D II.

Not too surprising - I don't think the EOS 1 has been made since about 1995.

Best regards,

Doug

44

Lenses / Re: Lens filter: step-down adapter ring, or not?

« on: April 22, 2011, 12:48:35 PM »

2. Get a step-down 77-72mm adapter ring

I think you are speaking of a 72-77 mm step-up adapter ring. (The description, both numerical and verbal, goes in the direction of lens size -> filter size.)

Here's an example:

http://www.bhphotovideo.com/c/product/98873-REG/General_Brand_72_77_72mm_77mm_Step_Up_Ring_Lens.html

Best regards,

Doug

45

EOS Bodies / Re: Question about RAW

« on: April 20, 2011, 10:50:06 PM »

My understanding of RAW is that it is simply the data "as-is" read from the sensor and saved on the memory card with no processing applied. However, I found that the color temp as set in a 50d directly affects the color temp of the saved RAW image. Are other in-camera functions applied to RAW as well?

The white balance color correction setting in the camera does not have any effect on the raw data.

However, that setting is saved (in a technically-detailed way) in the metadata of the raw file.

Then,  when the raw data is "developed" in external software to a JPEG or TIFF file, color correction is then applied, as set by the operator in any of various ways. One option is for the operator to tell the software to use the color correction that was set in the camera (which the software can read from the metadata) - the same color correction that the camera would have (or did) use in the in-camera generation of a JPEG file for the shot. But that is an explicit choice by the operator.

Best regards,

Doug