Lens Crop Factor

SkipD wrote in post #11897461
While what you say is technically true, the extreme majority of photographers that I have interfaced with over the last 50 years or so have generally used the term "telephoto" to refer to any lens with a focal length longer than the "normal" focal length for a given camera format.

In common photography parlance, even though it isn't quite technically correct, "telephoto" is roughly the opposite of "wide-angle".

Skip, you started a battle with that statement. However, what you said is common belief. I've always thought, and also heard that any lens longer than a "normal" lens (usually a 50mm on a 35mm format camera) was considered a telephoto.

We can all argue about what constitutes "telephoto". We can all argue about what constitutes "wide angle". We can also argue about the meaning of the term "heavy duty".

All that truly matters is your fine explanation. I've seen it posted numerous times, and if someone "doesn't get it" from your explanation, they probably never will.

I had an issue with FL when switching to digital as I bought a 1.6 crop. After a week of playing, I learned the "old" versus "new". It wasn't that difficult!

I guess this topic will never end!

melcat wrote in post #11897738
As for your numerous posts on "crop factor", I would draw your attention to the EXIF tag "35mm equivalent focal length". It's an accepted enough term for cameras to actually multiply by their crop factor and stick it in the image metadata. I have no problem with the term "equivalent focal length" (with the "35mm" being implicit). As an ex-medium format shooter, I'd rather the convention had settled on angle of view (2 required for each lens of course), but it is what it is and "35mm equivalent focal length" is established and useful.

The "35mm equivalent focal length" value (applied to a lens used on a camera that has a different format than 24mm X 36mm) can be useful to those of us who have the fields of view of various focal lengths on a 35mm film camera indelibly imprinted in our brains.

However, the newbie who started with an APS-C format camera will have very little advantage if he/she tries to "convert" all of his/her lens focal lengths to "35mm equivalent focal lengths" before committing the field of view on the APS-C camera to memory. In my opinion, this effort would actually be counter-productive to the newbie, especially if the newbie is not planning to migrate to a 35mm film format camera any time soon.

In the "olden days", none of us used a "crop factor" calculation when switching camera formats. When I would pick up my 6x6 camera, all I had to know is that the "normal" lens for it was an 80mm lens and the "normal" lens for my 35mm film cameras was a 50mm lens. Choosing other focal lengths was simply based on comparison of the normal to the desired focal length for a change in field of view.

SkipD wrote in post #11897950
The "35mm equivalent focal length" value (applied to a lens used on a camera that has a different format than 24mm X 36mm) can be useful to those of us who have the fields of view of various focal lengths on a 35mm film camera indelibly imprinted in our brains.

However, the newbie who started with an APS-C format camera will have very little advantage if he/she tries to "convert" all of his/her lens focal lengths to "35mm equivalent focal lengths" before committing the field of view on the APS-C camera to memory. In my opinion, this effort would actually be counter-productive to the newbie, especially if the newbie is not planning to migrate to a 35mm film format camera any time soon.

In the "olden days", none of us used a "crop factor" calculation when switching camera formats. When I would pick up my 6x6 camera, all I had to know is that the "normal" lens for it was an 80mm lens and the "normal" lens for my 35mm film cameras was a 50mm lens. Choosing other focal lengths was simply based on comparison of the normal to the desired focal length for a change in field of view.

^^^
In fact most of today's dSLR newbies not only started with digital P&S (with its even more shrunken and not-standardized sensor size!), but if they had any experience at all with 135 film, it was most likely in the context of a P&S which had a zoom lens with NO INDICATED FL SETTING (only a range) that their eyes and brain could calibrate itself to!

'Crop factor' has no benefit at all, other than when a prior owner of a 135 format SLR (where explicit FL is even discernible on a zoom lens!) moves to APS-C dSLR, to help them initally choose the appropriate FL for the smaller format. After they have worked in APS-C for a while, the numerical conversion isn't even performed...if I want 'normal' I pick up 30mm, if I want 'ultra wide' I pick up 15mm, no arithmetic in the thought process.

"someone who is new to using a DSLR really doesn't have any preconceived notions of how a 50mm lens might have worked on other image formats"

Yep that's right on target. Frame your object & shoot. If not what you want, adjust camera and re-shoot. Dont get lost in minutia & details about the lenses.

The only time people should be concerned with crop factor is when going from a crop to a ff camera and wondering what difference it will make. Just shoot the things. A 50 is not an 80, its a 50, with less field of view

Wilt wrote in post #11898511
'Crop factor' has no benefit at all, other than when a prior owner of a 135 format SLR (where explicit FL is even discernible on a zoom lens!) moves to APS-C dSLR,...

You couldn't be more wrong.

Crop factor is one of the most BASIC things you need to be aware of if you are on these boards.

Understanding crop factor in general is vital to communication about photography. Not understanding what it is and how it affects your photos leave you dazed and confused when you read posts on photography discussion boards like this one.

So if you have a friend who only ever talks to you about photography then yeah, you can gloss over it since you are explaining everything and can allow for it to start with. Of course if they ever buy a photography book, visit photography sites, or go to a camera store, they will be like "WTF"? So even then leaving them in ignorance is probably not the best idea.

Since the poster is ON THESE BOARDS, where crop factor is assumed as a given piece of knowledge in almost all discussions, it is important that he has a working understanding of it so he can understand the discussions here.

arentol wrote in post #11899402
Crop factor is one of the most BASIC things you need to be aware of if you are on these boards.

Understanding crop factor in general is vital to communication about photography. Not understanding what it is and how it affects your photos leave you dazed and confused when you read posts on photography discussion boards like this one.

The only reason that folks on the forum need to be aware of the "crop factor" facts (and the reason that I publish what I do to help folks understand) is so that they can wade through the tons of first class bovine excrement that get posted about the "crop factor" without being totally confused about the truth.

arentol wrote in post #11899402
You couldn't be more wrong.

Crop factor is one of the most BASIC things you need to be aware of if you are on these boards.

Understanding crop factor in general is vital to communication about photography. Not understanding what it is and how it affects your photos leave you dazed and confused when you read posts on photography discussion boards like this one.

So if you have a friend who only ever talks to you about photography then yeah, you can gloss over it since you are explaining everything and can allow for it to start with. Of course if they ever buy a photography book, visit photography sites, or go to a camera store, they will be like "WTF"? So even then leaving them in ignorance is probably not the best idea.

Since the poster is ON THESE BOARDS, where crop factor is assumed as a given piece of knowledge in almost all discussions, it is important that he has a working understanding of it so he can understand the discussions here.

The CONCEPT of 'crop factor' may be useful to understand (so you can then ignore the BS you read)...

...but the practical USE of 'crop factor' is valueless unless you have worked in the 24x36mm format and understand what-FL-does-what within that context.

Mankind has gone from photographic format to photographic format for over 100 years and never used the stupid concept , until digital SLRs with shrunken sensors (APS) came about -- before FF became economically viable for the consumer. APS is a different format from 135/FF, and the use of 'crop factor' is as pointless now as it ever was in the historical sequence of every other format size to ever exist at the same time.


PS Did I mention that 135 format is 3.9x crop factor of 4"x5" large format film cameras? and does it have any significance to you? No, and No.

Many point and shoot cameras (where there are all sorts of sensor sizes) have their lenses labelled in 35mm equivalent focal lengths to enable a comparison across the plethora of different formats. That's how I know my G9 lens equates to a 35-210mm zoom - otherwise I wouldn't know what 7.4-44.4mm was going to give me. Obviously in use I just zoom to get the framing I want (having first chosen my perspective, right Skip?), but say I see a new camera with a 4.2-126mm zoom, I can't easily compare until I find that this one equates to 24-720mm.

On a separate note, it's users of cameras like that latter one (I chose the Fuji FinePix HS10 as an example of extreme zoom range) who are staggered to find they'll have to part with £10,000 to get a Canon lens of equivalent magnification for their new 5D MarkII.

Madweasel wrote in post #11900748
Many point and shoot cameras (where there are all sorts of sensor sizes) have their lenses labelled in 35mm equivalent focal lengths to enable a comparison across the plethora of different formats. That's how I know my G9 lens equates to a 35-210mm zoom - otherwise I wouldn't know what 7.4-44.4mm was going to give me. Obviously in use I just zoom to get the framing I want (having first chosen my perspective, right Skip?), but say I see a new camera with a 4.2-126mm zoom, I can't easily compare until I find that this one equates to 24-720mm.

On a separate note, it's users of cameras like that latter one (I chose the Fuji FinePix HS10 as an example of extreme zoom range) who are staggered to find they'll have to part with £10,000 to get a Canon lens of equivalent magnification for their new 5D MarkII.

Exactly.... And so when coming from P&S to DSLR you need to understand crop factor if you want to purchase lenses to cover the same effective focal lengths as your P&S covered. So you have to convert the P&S up to 35mm, then convert that back down to APS-C. If you don't understand crop factor you can't do this. Another reason why dslr owners need to understand crop factor.

^^^all of this is why i say to forget about crop factor until you need to learn about it....

So you can visualize that what extremes of this range would equate to...at the wide end, or at the tele end. But have you any idea of the 'ideal waist up portrait' FL from having shot that with the G9? No because the G9 does not tell you what intermediate FL your lens is set to when you took that shot. You know, "I made this wonderful portrait shot somewhere in the range of 35-210mm, but I have no idea what lens to begin to buy for my new dSLR", apart from buying a 35-210mm zoom.

Wilt wrote in post #11900402
The CONCEPT of 'crop factor' may be useful to understand (so you can then ignore the BS you read)...

...but the practical USE of 'crop factor' is valueless unless you have worked in the 24x36mm format and understand what-FL-does-what within that context.

Mankind has gone from photographic format to photographic format for over 100 years and never used the stupid concept , until digital SLRs with shrunken sensors (APS) came about -- before FF became economically viable for the consumer. APS is a different format from 135/FF, and the use of 'crop factor' is as pointless now as it ever was in the historical sequence of every other format size to ever exist at the same time.


PS Did I mention that 135 format is 3.9x crop factor of 4"x5" large format film cameras? and does it have any significance to you? No, and No.

Actually Yes, you did mention that, just now. And you are right, it isn't significant to me. But then again I am pretty unlikely to go on a large-format lens discussion board, ask what a good focal length is for portraits on 4x5, find out it is 200mm, and therefore go out and purchase a 200mm lens for my Canon APS-C camera. In other words, of course it has no significance to me, because it is entirely irrelevant to the point at hand.

However, I am LIKELY to come on this board and find out that 85mm is a good focal length for indoor portraits. If I didn't understand crop factor I might just go ahead and purchase an 85mm lens for indoor portrait use only to find out later it is too long a focal length on my crop camera.

If only I had understood WTF CROP FACTOR was so I could get it right the first time.


Don't get me wrong, I know exactly what you are saying and I agree crop factor is a non-concern while taking photos. But it is still something that people need to understand to communicate about camera lenses and such for as long as we have lenses that are designed to fit on cameras of 3 entirely different formats....

It would be different if EF lenses didn't fit on APS-C cameras, and if there was yet another lens system for APS-H cameras. Then it truly would be irrelevant because, for instance, we would have 3 separate forums for each lens type here. But that isn't the case and so in order to understand discussions about lenses, and to be able to make informed decisions about what lenses to purchase, you must understand crop factor. Then once you have the right lens you can just use it and not worry about the crop factor thing.

Wilt wrote in post #11900402
PS Did I mention that 135 format is 3.9x crop factor of 4"x5" large format film cameras? and does it have any significance to you? No, and No.

I know that I'm an outlier in the general population, but I have found it very useful to know the crop factor when dealing with larger formats. Going out with a DSLR and seeing with my own eyes the FOV that I would get with different lenses on my film cameras is a lot faster and cheaper than buying and returning lenses on ebay until I find the focal length I need.

arentol and krb, both of you make your appropriate comments simply because both of you have experience in different format contexts, with specific FL. But if you come from a digital P&S, you have no clue where in the FL range you took a shot, because the camera does not tell you at all. Read post 27 to understand that problem...and that is the context that so many dSLR users come from, when they buy their first used Canon 30D or new T2i.

The crop factor concept is not entirely useless to everyone, but it is a useless source of confusion to most.