Crop cameras, crop factors, focal length, FOV, DOF and other mysteries and beliefs.

jgoetz4

dmmattix wrote:

Yes but with a 1.6 crop the 10-22 works out to be just about a 16-35. However for approximately the same price as the 10-22 you can get the 17-40 F4L to cover just about the same range.

Good Morning,
I will pass along what I have read on other forums regarding 'crop factors'.
It's not a true magnification from what I gather, but rather crops off the image. It was best explained to me that an individual is looking at a tree through 2 different windows, one measuring 24" x 36" , and the second measuring 15" x 23". The tree is still the same distance in the second window, just cropped.
Have a good day
Jim...

dmmattix

jgoetz4 wrote:

Good Morning,
I will pass along what I have read on other forums regarding 'crop factors'.
It's not a true magnification from what I gather, but rather crops off the image. It was best explained to me that an individual is looking at a tree through 2 different windows, one measuring 24" x 36" , and the second measuring 15" x 23". The tree is still the same distance in the second window, just cropped.
Have a good day
Jim...

Since my screw up started this...

The crop concept and name came from the concept of cropping in digital editing and before that cropping with the easel while printing in the darkroom. To take your example just a bit differently. If you stood in a spot and had both a 40D and a 5D with a 50mm lens and photographed a tree far enough away to fill the viewfinder of the 5D with both cameras and the same lens. You then print both images uncropped within Photoshop. The tree in the shot from the 5D would fill the picture while the shot from the 40D would not show the entire tree.

I have never tested it but I suspect a teleconverter has a similar effect as does a digital zoom on many point and shoots.

What does not change is the perspective and I do not feel qualified to explain that completely (I am sure someone like Ziggy will).

jgoetz4

dmmattix wrote:

Since my screw up started this...

The crop concept and name came from the concept of cropping in digital editing and before that cropping with the easel while printing in the darkroom. To take your example just a bit differently. If you stood in a spot and had both a 40D and a 5D with a 50mm lens and photographed a tree far enough away to fill the viewfinder of the 5D with both cameras and the same lens. You then print both images uncropped within Photoshop. The tree in the shot from the 5D would fill the picture while the shot from the 40D would not show the entire tree.

I have never tested it but I suspect a teleconverter has a similar effect as does a digital zoom on many point and shoots.

What does not change is the perspective and I do not feel qualified to explain that completely (I am sure someone like Ziggy will).

:
Good Afternoon,
Interesting discussions going on here
http://www.fredmiranda.com/forum/topic/612465/1#5404848
Just scroll down the page.
Have a good day
Jim...

ziggy53

Do I take it that people would appreciate an explanation, with examples, of the relationship between "crop factor", Field-of-View/Angle-of-View, focal length, chip sizes, relative magnification and total magnification?

dmmattix

ziggy53 wrote:

Do I take it that people would appreciate an explanation, with examples, of the relationship between "crop factor", Field-of-View/Angle-of-View, focal length, chip sizes, relative magnification and total magnification?

I for one would like to hear the relative vs total magnification differences.

jgoetz4

ziggy53 wrote:

Do I take it that people would appreciate an explanation, with examples, of the relationship between "crop factor", Field-of-View/Angle-of-View, focal length, chip sizes, relative magnification and total magnification?

Good Afternoon Ziggy,
That might help to explain things a bit I've heard arguments both ways that suggest: 1) it's only an FOV equivalent to a 1.6 magnification ( that's how I remember the tree picture being the same distance in both windows, just cropped) or 2) it is a magnification but it cannot equal the same resolution as the true magnification. Physics is involved in one these scenarios Thanks.
Have a good afternoon
Jim...

ziggy53

OK, I'll build something. Give me a week or so to build an animation and do some comparative examples. I'll propose some definitions and standards which, if I do my job properly, should clarify some things and get us all talking in a similar fashion.

I'll leave a link here, but it will be a new thread somewhere.

dmmattix

ziggy53 wrote:

OK, I'll build something. Give me a week or so to build an animation and do some comparative examples. I'll propose some definitions and standards which, if I do my job properly, should clarify some things and get us all talking in a similar fashion.

I'll leave a link here, but it will be a new thread somewhere.

Excellent and thanks Ziggy.

ccpickre

I don't know if it's been mentioned, but wouldn't a used 5D be better for landscape photography? (or did they say widlife specifically)

I would think the nature of the full frame sensor would work better for Landscape/nature.

As for wildlife, I guess the 40D is nice, but if you already have the 20D get a used 5D for nature and landscape.

That's just me though, I am really wanting a 5D now. Got an Xti, and a 40D and now i want more. My dad has started me down a viscious cycle of never ending camera addictions (I already want the XSi and 5D MkII now. Plus a 1DS MkIII. I even have a jonsing for the D300 or D3, whichever is the better one. And don't get me started on lenses)

NeilL

Hi ziggy53

Many thanks for your very generous offer.

I'm very much looking forward to coming to grips with these tricky issues - I'm sure I will with your help!

Neil

ziggy53 wrote:

OK, I'll build something. Give me a week or so to build an animation and do some comparative examples. I'll propose some definitions and standards which, if I do my job properly, should clarify some things and get us all talking in a similar fashion.

I'll leave a link here, but it will be a new thread somewhere.

jgoetz4

Morning Folks,
Here's one for the road until Ziggy shows his demonstration
Have a good day
Jim...

http://forums.dpreview.com/forums/readflat.asp?forum=1029&message=26418186&q=1+6x+crop+factor&qf=m
Re: Crop Question NEW
santa - 1 month ago
This is one of the most widely misunderstood issues with regard to DSLR's. Your understanding is correct. I can't speak authoritatively to the third question, but people who say "my 400mm lens is really a 640 on my camera" just don't get it. As one person pointed out recently, if all it took to turn a 400mm lens into a 2000mm lens was to use a smaller sensor, we'd all have super telephoto cameras with tiny sensors. The only thing the smaller sensor does is record less field of view. You can compare how many pixels are in a 1.6 to how many are in a 1.0 and talk pixel density and such but those are really separate issues. Just keep in mind a 400mm lens is still a 400mm lens on either camera; on a full crop it shows all of the image it sees. On a 1.6 crop, it simply is able to record less of the image on the sensor. Nothing more, nothing less.

[COMPLAINT]
[REPLY]

kdog

jgoetz4 wrote:

The only thing the smaller sensor does is record less field of view. You can compare how many pixels are in a 1.6 to how many are in a 1.0 and talk pixel density and such but those are really separate issues. Just keep in mind a 400mm lens is still a 400mm lens on either camera; on a full crop it shows all of the image it sees. On a 1.6 crop, it simply is able to record less of the image on the sensor. Nothing more, nothing less.

Well, that's one way of looking at it. Here's another. By definition, the longer the lens, the narrower the field of view. So by saying "less of the field", that's the same as saying longer focal length. That narrower field is applied to entire sensor resolution. So pixel quality issues aside, isn't that really higher magnification?

ccpickre

kdog wrote:

Well, that's one way of looking at it. Here's another. By definition, the longer the lens, the narrower the field of view. So by saying "less of the field", that's the same as saying longer focal length. That narrower field is applied to entire sensor resolution. So pixel quality issues aside, isn't that really higher magnification?

Higher mag at the sacrifice of distance though. I think it's more of an "it imitates" the "xxx" length, it doesn't actually extend to it. A 600 on a full body would still be 600, while a 400 on a crop would still be 400 with the 600 field.

At least that's how I've always pictured it.

dmmattix

ccpickre wrote:

Higher mag at the sacrifice of distance though. I think it's more of an "it imitates" the "xxx" length, it doesn't actually extend to it. A 600 on a full body would still be 600, while a 400 on a crop would still be 400 with the 600 field.

At least that's how I've always pictured it.

I had been waiting for Ziggy's more detailed explanation but since the topic has opened up again. ..

The only thing I had a problem with in Jim's original description was the 'magnification' statement. I believe the crop deal works for the picture like the Teleconverters do. The crop sensor only covers a portion of the image circle provided by full frame lense hence the name 'crop'. The TC works like a magnifying glass to make that image circle bigger and the sensor covers less of it hence cropping also. I am sure someone will correct me if I am wrong (like that has never happened) on the TC issue but from when I used one on a Pentax Spotmatic that was the way it worked.

What I am hoping Ziggy's explanation will cover is more the perspective and depth of field issues that neither the TC or the crop sensor impact. In that sense a 300mm lens is still a 300mm lens.

Regards,

jgoetz4

dmmattix wrote:

I had been waiting for Ziggy's more detailed explanation but since the topic has opened up again. ..

The only thing I had a problem with in Jim's original description was the 'magnification' statement. I believe the crop deal works for the picture like the Teleconverters do. The crop sensor only covers a portion of the image circle provided by full frame lense hence the name 'crop'. The TC works like a magnifying glass to make that image circle bigger and the sensor covers less of it hence cropping also. I am sure someone will correct me if I am wrong (like that has never happened) on the TC issue but from when I used one on a Pentax Spotmatic that was the way it worked.

What I am hoping Ziggy's explanation will cover is more the perspective and depth of field issues that neither the TC or the crop sensor impact. In that sense a 300mm lens is still a 300mm lens.

Regards,

Good Afternoon,
While you are waiting for Ziggys examples and explanations concerning this issue, why not visit the above link to dpreview.com and do some research yourself. That's why I posted it.
Have a good day
Jim...

kdog

jgoetz4 wrote:

Good Afternoon,
While you are waiting for Ziggys examples and explanations concerning this issue, why not visit the above link to dpreview.com and do some research yourself. That's why I posted it.
Have a good day
Jim...

Reading an anonymous person's opinion posted on the internet doesn't exactly qualify as research.

Cheers,
-joel

dmmattix

jgoetz4 wrote:

Good Afternoon,
While you are waiting for Ziggys examples and explanations concerning this issue, why not visit the above link to dpreview.com and do some research yourself. That's why I posted it.
Have a good day
Jim...

I actually HAVE read it. It actually agrees with my magnification point. The real issue they were discussing was the quality that comes from that magnification (specifically the blur). From the shots that we see around here shot with 10D/20D/30D/40D/Digital Rebel/D100/D200/etc I believe the blur issue is pretty well contained. Again we have the same issues when we put 1.4TC's on telephotos, shoot with crop cameras, well hopefully you get my drift.

I don't like religious discussions because both sides claim they win and nothing ever gets resolved so I will be awaiting Ziggy's presentation and use it to hopefully improve my knowledge.

Regards,

kdog

dmmattix wrote:

I actually HAVE read it. It actually agrees with my magnification point. The real issue they were discussing was the quality that comes from that magnification (specifically the blur). From the shots that we see around here shot with 10D/20D/30D/40D/Digital Rebel/D100/D200/etc I believe the blur issue is pretty well contained.

What blur issue? Are you saying that pictures taken with telephoto lenses on crop sensor cameras are any less sharp than those taken with a full frame camera?

jgoetz4

kdog wrote:

What blur issue? Are you saying that pictures taken with telephoto lenses on crop sensor cameras are any less sharp than those taken with a full frame camera?

I think he means bokeh. The out of focus areas.
Have a good day
Jim...

jgoetz4

I actually HAVE read it. It actually agrees with my magnification point. The real issue they were discussing was the quality that comes from that magnification (specifically the blur). From the shots that we see around here shot with 10D/20D/30D/40D/Digital Rebel/D100/D200/etc I believe the blur issue is pretty well contained. Again we have the same issues when we put 1.4TC's on telephotos, shoot with crop cameras, well hopefully you get my drift.

By adding a tc, you magnify the image with optics, not just a crop.

I don't like religious discussions because both sides claim they win and nothing ever gets resolved so I will be awaiting Ziggy's presentation and use it to hopefully improve my knowledge.

I don't believe religion has anything to do with it I have
seen examples and heard arguments both ways and I believe that the magnification is 'interpolated' with the DOF of a 1.6x lens. It sounds like you will take Ziggy's word as Gospel when he shows his examples. Oh, wait a minute, maybe this does have something to do with religion
Have a good day
Jim...
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ziggy53

I created a new thread for this discussion because we pretty well trashed the previous thread.

Please continue the discussion here but remember to keep it on topic and civil.

jgoetz4

ziggy53 wrote:

I created a new thread for this discussion because we pretty well trashed the previous thread.

Please continue the discussion here but remember to keep it on topic and civil.

Good Afternoon Ziggy,
You know we are all civil Just trying to show links to both sides of the issue and let the members judge for themselves. There were some really heated, name calling debates last year over at dpreview.com. That's not called for on any level. After all, we are here to help, learn and share
Have a good day
Jim...

jgoetz4

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Quote:
Originally Posted by jgoetz4
Good Afternoon,
While you are waiting for Ziggys examples and explanations concerning this issue, why not visit the above link to dpreview.com and do some research yourself. That's why I posted it.
Have a good day
Jim...


Reading an anonymous person's opinion posted on the internet doesn't exactly qualify as research.

No it doesn't, but the internet itself is an excellent place to start, and dpreview.com is an excellent place to start with.
Have a good day
Jim...
Cheers,
-joel
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claudermilk

I suspect part of the issue with suggesting using DPR is, while I'm sure there are a number of knowledgeable users there, it's generally considered a toll den and better avoided by those wishing to carry on meaningful discussions.

My understanding of the whole crop thing is it isn't true magnification. You are just cropping out the center of the image circle, which give the same FOV of a longer lens and the impression of magnification. So on a 1.6 crop sensor a 50mm lens gives approximately the same FOV of an 85mm lens. The perspective stays the same since you have not moved. Bokeh will be different & DOF will be different. But it's still an image projected by a 50mm lens. In the end, I don't worry too much about it, I just put the lens that I know will give me the framing I want on the camera and shoot the image I am after (or at least try...).

jgoetz4

claudermilk wrote:

I suspect part of the issue with suggesting using DPR is, while I'm sure there are a number of knowledgeable users there, it's generally considered a toll den and better avoided by those wishing to carry on meaningful discussions.

My understanding of the whole crop thing is it isn't true magnification. You are just cropping out the center of the image circle, which give the same FOV of a longer lens and the impression of magnification. So on a 1.6 crop sensor a 50mm lens gives approximately the same FOV of an 85mm lens. The perspective stays the same since you have not moved. Bokeh will be different & DOF will be different. But it's still an image projected by a 50mm lens. In the end, I don't worry too much about it, I just put the lens that I know will give me the framing I want on the camera and shoot the image I am after (or at least try...).

Good Morning Chris,
This is taken from Wikipedia
Digital Photography Review
From Wikipedia, the free encyclopedia
(Redirected from Dpreview.com)

Digital Photography Review (established November 1998) is a website about digital cameras and digital photography. The website has reviews of digital cameras, buying guides, user reviews, and very active forums for the individual cameras as well as general photography forums. The website has a large database with information about the individual digital cameras.

www.dpreview.com is one of the top 1000 most visited websites on the Internet, according to Alexa Internet[1]. The website itself claims that "These days the site is one of, if not the, premium digital photography site with an audience of seven million unique visitors a month reading over one hundred million pages"[2].
I guess with that many monthly visitors, there are bound to be a few trolls along with thousands of 'knowledgeable users'
Have a good day
Jim...

kdog

claudermilk wrote:

My understanding of the whole crop thing is it isn't true magnification. You are just cropping out the center of the image circle, which give the same FOV of a longer lens and the impression of magnification. So on a 1.6 crop sensor a 50mm lens gives approximately the same FOV of an 85mm lens. The perspective stays the same since you have not moved. Bokeh will be different & DOF will be different. But it's still an image projected by a 50mm lens. In the end, I don't worry too much about it, I just put the lens that I know will give me the framing I want on the camera and shoot the image I am after (or at least try...).

This is basically what several folks above said as well. What it overlooks is the fact that this reduced FOV is projected over the entire sensor, giving you a higher pixel density. Pixel density is very important because it's what gives you detail in the shot. In order to get the same pixel density as the crop body camera in its reduced FOV, you'd have to compare it to a full frame camera with crop-factor times more pixels. So in the case of the Canon 40D, you'd have to compare it to a 16.1 MP full frame camera. In that case, you could truly crop the image from the full-frame and end up with the same magnification as the crop-body for the same FOV. The only camera that fits that bill is the Canon Mark 3 1DS. For all other cameras in the Canon line, the 40D gives the most magnification, given equal lenses, at equal levels of detail.

KED

ziggy53 wrote:

Do I take it that people would appreciate an explanation, with examples, of the relationship between "crop factor", Field-of-View/Angle-of-View, focal length, chip sizes, relative magnification and total magnification?

Would you do some kind of "top of the forum" announcement when it's ready? This is one weird thread (no offense to anyone intended), and I'd prefer to wait for your authoritative explanation.

jthomas

This is a very simple concept, and I don't understand why people have so much trouble with it. I think they try to make it harder than it is.

Please consider the diagram below. Circle "A" is the image circle thrown on the plane of the sensor by a standard lens.

Rectangle "B" represents the "full-frame" sensor of a few currently available DSLR's (Canon 5D, Nikon D3, etc.) which is very close to the size of the sensitive region of a frame of 35mm film.

Rectangle "C" represents the size of the sensor of most DSLRs (Canon 30D, Nikon D200, etc.).

Obviously "C" will record only the center of the image, and will give the same effect as using a lens with a longer focal length.

That's all there is to it (if both sensors have the same number of pixels).

kdog

jthomas wrote:

Obviously "C" will record only the center of the image, and will give the same effect as using a lens with a longer focal length.

That's all there is to it (if both sensors have the same number of pixels).

Bingo. That's exactly what I was trying to say, although you said it more concisely.

NeilL

kdog wrote:

This is basically what several folks above said as well. What it overlooks is the fact that this reduced FOV is projected over the entire sensor, giving you a higher pixel density. Pixel density is very important because it's what gives you detail in the shot. In order to get the same pixel density as the crop body camera in its reduced FOV, you'd have to compare it to a full frame camera with crop-factor times more pixels. So in the case of the Canon 40D, you'd have to compare it to a 16.1 MP full frame camera. In that case, you could truly crop the image from the full-frame and end up with the same magnification as the crop-body for the same FOV. The only camera that fits that bill is the Canon Mark 3 1DS. For all other cameras in the Canon line, the 40D gives the most magnification, given equal lenses, at equal levels of detail.

Good post. Thanks.

jgoetz4

Interesting reading on x factor, fov, aov, etc
Morning Folks
The following link provides a very good in depth look at these issues. Make a pot of coffee, turn off your cell phones and prepare to spend some time reading this article. It is a bit lengthy, but very detailed.
Have a good day
Jim...
http://www.digitaldingus.com/articles/fov/fovef.php