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05-26-2012, 07:27 AM   #16
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@ RioRico Thanks for contributing! I always appreciate you sharing your technical knowledge. If I knew you in person I would no doubt end up describing you as the walking encyclopedia type, which is entirely meant as a complement. My Dad used to let me take his K1000 out sometimes when I was a kid and in my photography class in junior high we used K1000s but that's as far as my film experience goes. That might change once I pick up a film body. I would really like to strap my FA Limiteds on one to get more out of them. I'm also quite drawn to the 645 system. I like hearing about the film antecedents, however trivial they may seem.

QuoteOriginally posted by RioRico Quote
Yes, each format is independent, with various strengths and weaknesses, and it behooves toggers to learn how to use their cameras. Back in the day, I might shoot 135/HF, 135/FF, 6x6/MF, and 9x12/LF on the same day, sometimes with the same lenses. My colleagues and I didn't think of crop factors and equivalences. We learned what different lenses and films would do with each format we used.
I really like that comment; it rings true to me, even in this digital age.

05-26-2012, 08:24 AM   #17
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QuoteOriginally posted by TomTextura Quote
I like hearing about the film antecedents, however trivial they may seem.
As you may gather, I read histories of media. How we got to where we are with graphics and text, images and sound and whatever, I find just endlessly fascinating.

Camera history: SLRs were built in the 1500s -- for sketching, not photographing, but everything was there except shutter and film. Film SLRs didn't just pop-out of the Exakta workshop in the 1930s but were being used by WWI -- big honking 4x5 SLRs for combat photographers. 35mm half-frame cameras (with frames about the size of APS-C sensors) long preceded the Olympus Pen-FT; the first was from about 1905, even before the double-frame Leica prototype.

And contemporary digital sensor formats derive from video and film predecessors, but also from display typography and painting+drawing standards going back many centuries. 4x5 and 8x10 print formats originated with... the standard size of a sheepskin, which could be cut and folded to those sizes for portable manuscript texts, something over a millennium ago. Damn, I love this stuff!
05-26-2012, 09:18 AM   #18
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Say you know a film user and he wants to take a picture with an equivalent fov to a 50mm lens, but on APSC. Would it be incorrect to say to him 'to get that you need to use a 35mm lens (a lens with the fl of 35mm)' - which is the 'equivalent focal length' line? I would propose that's much easier for someone to get their head around than the treatises outlined here!
05-26-2012, 09:33 AM   #19
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QuoteOriginally posted by ihasa Quote
Say you know a film user and he wants to take a picture with an equivalent fov to a 50mm lens, but on APSC. Would it be incorrect to say to him 'to get that you need to use a 35mm lens (a lens with the fl of 35mm)' - which is the 'equivalent focal length' line? I would propose that's much easier for someone to get their head around than the treatises outlined here!
For a film user and when the issue has already been described in terms of FOV sure, suggesting a 35mm for the EFL would be easy enough. Switch over to talking to a beginning photographer whose only somewhat familiar with the two main DSLR formats, FF and APS-C, and leave out the FOV detail and you may just be doing the person a disservice by only referring to EFL. I can admit, somewhat embarrassingly, that it had me tripped up at first. And from what I've read many people write online, they either were or still are tripped up about it too.


Last edited by TomTextura; 05-26-2012 at 09:35 AM. Reason: added "somewhat" to qualify familiar
05-26-2012, 09:59 AM   #20
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1. You get exactly the same magnification with a 50 mm lens on APS-c as you do on FF or any other camera, from the lens..
2. On any digital camera of any size, effective magnification increases with pixel density.

The difference between FF and APS-c has been and can be made up for by pixel density.

So in fact say you're taking a picture if a Hawk and you want the image to be 1000 pixels across, for clarity, somehow you've determined that will give you the level of sharpness you desire, and you can do that with 100 mm lens on an APS-c camera at 16mp. You also have a 12mp FF camera, To get your 1000 pixels on the FF camera you're going to need a 135 mm lens to make up for the lower overall sensor pixel per inch count, and then mulitply another 1.5 or go to 200 mm to have your image of said hawk from the same position give you your 1000 pixels.

If you have two 16 mp cameras then you still need a longer lens to achieve the same pixel count, because with a 16 mp FF the pixels are spaced further apart. To actually have an advantage the FF sensor has to be like the D800, it has to have the same pixel density as the APS-c sensor.

So in practice there is a very real 135 mm =200 mm effect, if they are both 16 mp cameras, because they both produce the same number of pixels but the APS-c is focused on a smaller area.

People have argued that the larger pixel sites give better images, but given the resolution of the K-5 and D800, those claims are at best questionable, and at worst, completely unsubstantiated. WIth very small sensor, such as in my Optio W90 I've noticed that purple fringing is more of a problem in some light. The problem being that such results are not necessarily predictable with any accuracy when talking about sensor. There are different manufacturers, different factories making different products. The sensor in different cameras are not directly comparable. So while you can say that 5 years ago the Canon guy who showed that the FF canon of the time took sharper pictures than a comparable APS-c model, neither of those sensors is rated as high as the K-5 sensor, so you're talking about a comparison of two inferior sensors that may or may not apply, but probably doesn't.

That being said, there are all kind of other factors to be considered, APS-c definitely will exagerate CA and PF if the lens isn't up to scratch, again, because of the higher pixel per inch count, but, let's not get crazy. Most of the time the value of the magnification with a shorter lighter lens is worth more than a bit of image degradation. We can talk the trade-offs all day, but if you think image 1000 pixels across and stop using outdated film language, it'll help things out, conceptually.
05-26-2012, 12:24 PM - 1 Like   #21
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If anyone would like to see how different film/sensor sizes stack up to each other and compare Depth of Field, Field of View, Angle of View, HyperFocal distances, etc. - I built a spreadsheet a while back to edumicate myself on how changing focal length, aperture and distance affected things.
I have columns for APS-C, 135/FF, 645D, 645, 67, and for fun 4x5 & 8x10. It's in Excel97 format so pretty much any current spreadsheet program should open it. It is pretty self-explanatory, and I've attached it for your entertainment.
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File Type: zip FORMAT_COMPARISONS_EN.zip (4.3 KB, 52 views)
05-26-2012, 12:29 PM   #22
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QuoteOriginally posted by ihasa Quote
Say you know a film user and he wants to take a picture with an equivalent fov to a 50mm lens, but on APSC. Would it be incorrect to say to him 'to get that you need to use a 35mm lens (a lens with the fl of 35mm)' - which is the 'equivalent focal length' line? I would propose that's much easier for someone to get their head around than the treatises outlined here!
I may have mentioned this earlier in this thread: You can equate the AOV of lenses by multiplying just the focal length by the format factor, but to figure the actual equivalence which includes DOF, factor in the aperture too. The format factor of my K20D sensor (diagonal is 28.1mm) is 1.54, not the 1.44 of nominal APS-C (diagonal is 30.1mm). This gives the following AOV+DOF equivalences:

* 50/1.2 on APS-C is about 77/1.8 on 135/FF (short-tele)
* 35/1.8 on APS-C is about 55/2.8 on 135/FF (long-normal)
* 28/2.5 on APS-C is about 43/3.8 on 135/FF ('normal')

I use AOV instead of FOV because FOV changes at different distances. There's the old ROT (rule of thumb) that changing FOVs from 28 to 35 to 43 to 55mm can be done by taking 2 or 3 steps forward or back for each increment.


Last edited by RioRico; 05-26-2012 at 12:35 PM.
05-26-2012, 12:46 PM   #23
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QuoteOriginally posted by RioRico Quote
I use AOV instead of FOV because FOV changes at different distances. There's the old ROT (rule of thumb) that changing FOVs from 28 to 35 to 43 to 55mm can be done by taking 2 or 3 steps forward or back for each increment.
Good point! AOV is the term I will stick with when discussing the difference b/w sensor formats and lenses in order to be more accurate.
05-26-2012, 12:55 PM   #24
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QuoteOriginally posted by Venturi Quote
I built a spreadsheet a while back to edumicate myself on how changing focal length, aperture and distance affected things.
Very nice! Thanks for sharing!
05-26-2012, 01:03 PM   #25
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QuoteOriginally posted by Venturi Quote
Advanced Photo System (APS) format is the brain child of Eastman Kodak. It debuted in 1996 and is comprised of three sub-formats:
H - High-definition 16:9 aspect
C - Classic (not crop!) 3:2 aspect
P - Panorama 3:1 aspect
Calling APS-C format sensors "cropped" is quite simply marketing mumbo-jumbo.
To add to the confusion, Canon saw fit to appropriate "APS-H" for its 1.3x crop 3:2 aspect sensor.

Also, APS films did use crop in that a "panorama" was just a regular width frame with the top and bottom cropped out. When I first learned about the APS format I was all excited thinking we would get frames where the width varied and the height remained constant, but I was mistaken.
05-26-2012, 04:14 PM - 1 Like   #26
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With rare exception, I compose based on what I see in my viewfinder. When DOF is of importance (fairly often), I shoot Av or manual and have my green button set to duplicate my old Super Program's stop-down lever. Even there, I care based on what I see, not what the math tells me is happening. So while most of this esoteric discussion is true, how many of us think about this as we are pushing the shutter release?

I remember the medium format fans explaining the same thing to 35mm camera users. This is one of those great discussions to have with fellow photographers over a pint at the pub on a dreary evening. And like a lot of those discussions, it really matters little outside those discussions.
05-30-2012, 06:39 AM   #27
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QuoteQuote:
Even there, I care based on what I see, not what the math tells me is happening.
Exactly... I don't know a single guy either from when I was in Photo Arts at Ryerson, to any of the working photographers I've known, who gave an owls hoot about the math or physics of lens performance. It's about getting your eye to the viewfinder and saying " I can work with this." That's a photographer. Analyzing charts for comparative depth of field etc. FOV etc. doesn't mean a thing, until you put your eye to the viewfinder and see what it looks like.

DoF is even more problematic. In the field I tend to bracket my f-stops.. shooting wide open, 5.6 11 and 22 or some other combination that makes sense based on the scene. It is so rare that the wide open shallow depth of field is the one I want to keep that I shudder whenever I hear about people wanting to pay big bucks to get it. I often find the images of those who seem to think shallow depth of field is really important, irritating. Quite simply stated. Shallow depth of field is more often a problem, not a solution.

But I digress, the point being, I often can't evaluate what I want from DoF until I'm looking through the lens. Math doesn't help with that.
05-30-2012, 06:59 AM   #28
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QuoteOriginally posted by normhead Quote
Exactly... I don't know a single guy either from when I was in Photo Arts at Ryerson, to any of the working photographers I've known, who gave an owls hoot about the math or physics of lens performance. It's about getting your eye to the viewfinder and saying " I can work with this." That's a photographer. Analyzing charts for comparative depth of field etc. FOV etc. doesn't mean a thing, until you put your eye to the viewfinder and see what it looks like.

DoF is even more problematic. In the field I tend to bracket my f-stops.. shooting wide open, 5.6 11 and 22 or some other combination that makes sense based on the scene. It is so rare that the wide open shallow depth of field is the one I want to keep that I shudder whenever I hear about people wanting to pay big bucks to get it. I often find the images of those who seem to think shallow depth of field is really important, irritating. Quite simply stated. Shallow depth of field is more often a problem, not a solution.

But I digress, the point being, I often can't evaluate what I want from DoF until I'm looking through the lens. Math doesn't help with that.
I would tend to agree, the only thing I really ever use math for, is if I know a specific venue subject and shooting location, i routinely go through the approximate (distance >>> focal length) calculation of
Image size = subject size x Focal length / distance
or some recomposed form of it to consider what lens or range of lenses I want to carry.

Aside from that, you are correct the viewfinder is all important.

Other useful uses of math are in manual flash calculations, and occasionally a more detailed distance and magnification calculation for macro, but generally the viewfinder rules.

My present obsession with wildlife only shows one thing, and I think we are on the same page, regardless of the depth of field we have it is generally never enough, therefore why do people get such fast lenses.
05-30-2012, 07:25 AM   #29
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QuoteQuote:
I would tend to agree, the only thing I really ever use math for, is if I know a specific venue subject and shooting location, i routinely go through the approximate (distance >>> focal length) calculation of
Image size = subject size x Focal length / distance
or some recomposed form of it to consider what lens or range of lenses I want to carry.
I think the issue here is you are just way more talented math wise than I am. I'm not sure I could actually do that even if I put my mind to it. My defense is to have every focal length in my bag when I go out. So for a shooter like me, Pentax's pancake lenses are priceless. I take my 21 ltd and 35 almost every where. I have to check my bag to see if they're with me, because based on weight and the space they take, it isn't obvious. I find much of the time, the 21 , 35 and 60-250 are enough. However that being said, at Niagara falls I used very lens plus the 10-17, 50mm 1.7, Tamron 90 and 18-135, and probably would have used the 15 ltd, 31 ltd and 70 if I owned them.

They should just set this case up at Niagara Falls so people like me can try things out in real life situations and decide what to buy next.

05-30-2012, 07:27 AM   #30
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QuoteOriginally posted by normhead Quote
But I digress, the point being, I often can't evaluate what I want from DoF until I'm looking through the lens. Math doesn't help with that.
I'm an amateur returning to SLR work with a K-r after letting my Super Program sit idle for several years when Ektachrome got harder to buy and while affordable digital was still playing catchup with film. One of my most used features on the Super Program was the depth of field preview lever next to the lens. This is a feature missing from from the K-r. For cripes sake, the digital lenses don't even have the focus distance and DOF scales engraved! Sure, I found that the green button was reprogramable to preview DOF, which I have done - at the expense of other useful functions.

I'm pretty sure this isn't true, but it almost seems to be a plot by the major camera manufacturers to not let us SEE what the lens will see during the exposure. Silly me. I thought the biggest reason for aperture priority automation was DOF control.
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