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Merlin66

Full Frame APS-C "crop factors" etc.

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Merlin66    843

It's cloudy.....
Why is it, twenty years after the demise of the SLR and 35mm film that we keep talking about full frame and various lens equivalents back to the 80's?
In AP Full frame etc. doesn't mean a thing!
Its the physical size (and pixel size) that makes the difference.....
I think there are amateurs who have never seen 35mm film......

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Craney    392
19 minutes ago, Merlin66 said:

I think there are amateurs who have never seen 35mm film......

... don't ask them to pop out and buy some emulsion .....

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ronin    3,700

There are worse so don't get bothered by it.

We have a "photographer" who dabbles into AP, who is still convinced, and tells everyone, that his 200mm lens on his aps sized DSLR's is rerally a 300mm lens and what a "good deal" he managred.

The fact that he has a 200mm lens immaterial of the camera just fails to get in, and it is the field of view that he has lost since his 200mm lens produces an image size of a 200mm lens but compared to a full frame he has the reduced field of a 300 lens.

The final result being he has a 200mm lens - no gain - and the reduced field - a loss. Overall he has lost out not gained.

One night he was saying to another photographer that really our 300mm lens are 400mm lens aren't they, the other guy knew the situatioon and couldn't really understand what he was so positive about. I think the other guys parting comment was that yours might be but I am sure mine is just a 300mm lens.

Also there are now a few "full frame" DSLR's and people are half familiar with the term. Were they ever 35mm anyway, film was measured a bit odd. And of course Medium Format which being only "Medium" was bigger then "Full".

24 minutes ago, Merlin66 said:

I think there are amateurs who have never seen 35mm film......

Quite a lot have little idea of film and to an extent of how things fit together, DSLR's are possibly too automatic.

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Tim    2,545

35mm film? Pffft! That was just mucking about, many of the professional industrial photographers my family used to produce prints for worked in medium format. We had to get the smaller glass negative slider out for the enlarger if anyone brought 35mm.

There was something magical, (and likely highly toxic!) about the smell and atmosphere of the darkroom. Would love to go back into one for a while to experience that again.

Sometimes if I con them into coming to have a look through my scopes, my family will comment that they don't know how I can work in the dark. Yet back in school days I used to hand load film cartridges with film from a large spool tin, doing the whole thing in complete darkness, astronomy is a walk in the park compared!

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RobertI    928
47 minutes ago, ronin said:

Were they ever 35mm anyway, film was measured a bit odd. And of course Medium Format which being only "Medium" was bigger then "Full".

I think this kind of proves the OP's point! :confused3: The categorisations are just not relevant today (if they ever were) and confusing but I totally understand why it's very hard to change this. Many software/apps still have a 3.5" floppy disc as the 'save' icon - when was the last time you used one of those? :cheesy:

Edited by RobertI
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ollypenrice    17,056

I am entirely allergic to the term 'crop factor' which has no meaning whatever in AP. I do use the term 'full frame' for my (roughly) 35mm fillm-eqivalent CCD chips, though, out of old habit. I hereby slap myself on the wrist!

If we were to follow the logic of the 'crop factor' nonsense to its conclusion we would only need a small enough chip to turn our camera lenses into the Hubble.

To hijack Ken's thread for a related plea to the AP industry:

What we want to know about a camera is its chip size (both sides and diagonal, without having to work them out) and its pixel size. Its pixel count can be thrown in but it serves no pressing purpose. We never get this most basic and essential information without grubbing around in Google for hours.

Other confusions imported from the camera world include the use of 'resolution' to mean pixel count (plain wrong) and (in tiny wee voice) the F ratio myth.

Olly

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Macavity    2,727

There are lots of things that are (genuinely) confusing? Ever hear the 
phrase "for historical reasons"? lol. But then I used to go to bed with 
the (my Dad's) Ilford Manual of Photography - Fifth edition (1958). :D
(Not trying to "top" folks, just a fact of life for an inveterate nerd?) lol

When my Dad bought a Zenit-E(!), I became familiar with the concept
of "general purpose" (50mm), "portrait" (85mm), "telephoto" (135+)
lenses etc. etc. When I was finally persuaded to move to a *modern*
DSLR, I learned of APS-C sensors... Full-Frame sensors... EF lenses. :eek:

Armed with that knowledge I bought my first (likely only!) CANON EF
(70-200mm f/4). But it took a while to be confident of the decision! :o

I'm not sure that "chip size" solves all problems? Video Astronomers
learn quite early on in the day that a "half inch" (diagonal) chip has
a diagonal of about 8mm -- Which is about 1/3" in my book. Heheh.
(Not mention our first 19" TV which seemed to also shortchange!) :p

Kudos KEN (the OP) and others who give worked examples / tables
in their books! This is not a simple issue though? "Society" seems to
have an aversion to the slightest technical content / knowledge! On
the other hand, today's scientists like to mock the idiot unintiate? :(

Lest I get too serious, maybe just a call to *appreciate* the efforts
of ALL those who try to answer questions on Astronomy Forums! :)

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JG777    374
4 hours ago, RobertI said:

I think this kind of proves the OP's point! :confused3: The categorisations are just not relevant today (if they ever were) and confusing but I totally understand why it's very hard to change this. Many software/apps still have a 3.5" floppy disc as the 'save' icon - when was the last time you used one of those? :cheesy:

I am just trying to remember the last time I saw a flying teapot and the circumstances that led up to it :icon_biggrin:

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Stub Mandrel    5,421

Some time I will do some REAL wide field with this:

yashicamat.thumb.JPG.d1d7f43e0ba9eb56c78a02c37a2e502c.JPG

8 hours ago, JG777 said:

I am just trying to remember the last time I saw a flying teapot and the circumstances that led up to it :icon_biggrin:

I used to have a green teapot with wings painted on the side etc.

I once saw Gong supported by Here and Now. I think the only difference was that the Divided Alien didn't appear with the latter. very different music but incredible musicianship.

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michael8554    409

I have never understood why APS etc cameras are advertised with crop factors. It just leads to the confusion ronin's friend has.

16mm, 35mm, 70mm are terms still relevant to the film and tv industries, but 35mm could be easily dispensed with in reference to dslr's,

Full Frame is an established and non confusing term, as are APS, Four Thirds, Full Frame, Medium Format, all dimensionless and the better for it.

Michael

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Alien 13    3,460

I think some of the confusion for me anyway is that full frame cameras often have bigger pixels and less of them so it you where to take a 20Mp full frame and shoot with say a 300 mm ish lens you would have an image on your screen with a certain size and DPI, now if you used a 20Mp cropped sensor with a 200mm ish lens you would end up with an almost identical image to the first with exactly the same resolution.

Alan

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ollypenrice    17,056
10 hours ago, Alien 13 said:

I think some of the confusion for me anyway is that full frame cameras often have bigger pixels and less of them so it you where to take a 20Mp full frame and shoot with say a 300 mm ish lens you would have an image on your screen with a certain size and DPI, now if you used a 20Mp cropped sensor with a 200mm ish lens you would end up with an almost identical image to the first with exactly the same resolution.

Alan

To be clear, I didn't mean this was tosh! It's part and parcel of the way we should discuss FOV and resolution in AP. For me the tosh lies in muddying the waters with crop factors.

Olly

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Alien 13    3,460
1 minute ago, ollypenrice said:

To be clear, I didn't mean this was tosh! It's part and parcel of the way we should discuss FOV and resolution in AP. For me the tosh lies in muddying the waters with crop factors.

Olly

Thanks Olly :icon_biggrin:

Alan

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Horwig    700
On 14/09/2017 at 08:24, ollypenrice said:

(in tiny wee voice) the F ratio myth.

Sorry Olly, could you speak up, I missed that bit, my eyes are not that good :icon_biggrin:

Edited by Horwig
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StuartJPP    4,543

Coming from a photography background it all makes sense to me but it is a bit of a mix and match as the majority of measurements are made equivalent to 35mm systems.

When people say "forget what you thought you knew about photography, astrophotography is completely different", I'd say that isn't true...there are some new things to discover but otherwise I find it very much the same...and physics tells us that...we are capturing photons at the end of the day.

Olly sums it up... Physical sensor size and pixel size of the sensor are the main things to understand in the astro world....

However we all know what size an APS-C sensor is physically...so the "resolution" will give you the pixel size using simple math (within reason, it doesn't include space between pixels).

Each to their own I say....the end result is what matters after all i.e. I just like making pretty pictures :icon_biggrin:

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RichM63    3,249

I think the waters are already muddy when AP is not specified as opposed to TP.

Two completely different fields IMHO with often confused overlapping confusing terminology and required criteria.

The lens becoming longer on a crop sensor DSLR is clearly a misunderstanding, but the small bird seeming to get bigger or nearer is I think where the confusion gets reinforced.

However, getting outside and taking pictures of whatever, is the important bit for the most part, here we are only a few folk that look to further our understanding of the kit involved.

Best, Rich

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happy-kat    3,022

I'm glad to have had the experience of darkroom work, smelly though it was. I personally like using a smaller sensor with a large lens as there's less vignetting, it suits me.

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RobertI    928
On 14 September 2017 at 13:07, JG777 said:

I am just trying to remember the last time I saw a flying teapot and the circumstances that led up to it :icon_biggrin:

Ah, well when you remember, please feel free to share with us! :icon_biggrin:

On 14 September 2017 at 21:33, Stub Mandrel said:

I once saw Gong supported by Here and Now. I think the only difference was that the Divided Alien didn't appear with the latter. very different music but incredible musicianship.

I'm very jealous, I wish I had the opportunity to see Gong and Divided Alien himself before he went to joint the giant teapot in the sky. I have actually come to appreciate Gong fairly recently with their brilliant musianship and quirky material. Planet Gong is up there waiting to be discovered!:happy10:

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Mr Spock    5,028

We get this all the time on photography forums. People with APS-C cameras referring to a 50mm lens as a 75mm equivalent... sigh. A 50mm lens is a 50mm lens, regardless of what camera you use it on.

Yes, a 50mm lens has a smaller field of view on APS-C than it does on FF. You could also say a 50mm lens on FF has a smaller field of views than on 6x6 (or 6x7) medium format.

People need to get 35mm out of their heads :wink2:

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