Equivalence (35mm vs APS-C, Prime vs Zoom, etc)

[Kym]

http://www.josephjamesphotography.com/equivalence/index.htm

The above link is to an essay on Equivalence, but is really about image quality (IQ).
Eg. Equivalent focal length from cropped vs 35mm sensors etc.

Remembering that Equivalence does not mean Equality.

Warning: The essay is long, detailed and very technical.
I think its well written and has some excellent technical arguments.
The Author (Joseph James) has done a brilliant job.

A small quote....

The debate between different sensor formats is very much like the debate between primes and zooms. While top-quality primes may have higher IQ, allow for a more shallow DOF, and be better suited for low-light photography, they do not zoom. That singular advantage of a zoom trumps all the advantages of a prime for many photographers, and so it is when comparing formats. It is not only a matter of whether one system is "better" than the other in terms of IQ, but at what display dimensions this difference becomes significant. For many, and likely most, it is more often a matter of available lenses, differences in DOF capabilities, and operational convenience, than it is a matter of IQ alone.

The bottom line is that we use a camera to create images. It is important to understand the advantages of any particular system as a whole, both in terms of IQ and operation. The purpose of equivalence is to help evaluate the IQ end of that consideration, and, in conjunction with our individual "quality threshold", make an informed choice as to which system, or systems, best meet our personal needs for the photography that we do.

Enjoy!

[Frisbee100]

Thanks for the link.

Yes, it does look like a big read. Maybe tonight when I go bed.

Fris

[Kym]

Any feedback on the essay?

[TOM]

Any feedback on the essay?

i'm going to sit down and immerse myself in this after lunch. i certainly don't agree with his first few lines in your quoted text, but it's a big essay. looking forward to it, thanks for the link.

EDIT: wow, just printed this, 64 pages!

[Kym]

i'm going to sit down and immerse myself in this after lunch. i certainly don't agree with his first few lines in your quoted text, but it's a big essay. looking forward to it, thanks for the link.
EDIT: wow, just printed this, 64 pages!

:D

As you said in another thread "...is full of contradictions, just as life and indeed photography is."

This puts a case and has some very deep thinking.
A prime lens will give better IQ (generally) than a zoom, but a zoom has practical benefits.
Is the resulting image good enough for purpose?

It is a very interesting and enlightening debate.

[reaction]

wow it's big, any chance for a 1 paragraph summary ;)

[Kym]

wow it's big, any chance for a 1 paragraph summary ;)

My take:

When comparing lenses, 35mm vs APS-C sensor, or other camera technology etc. make sure you are comparing an equivalent display results.
I.e. 100% crops and pixel peeping don't tell the true story.

Simplistically compare the result of a 4x6 print (or 8x12, or whatever) of each system
(equivalent - same effective FL (field of view), DoF, Effective Exposure (same light processed))
to get a real life equivalent comparison.
Then decide is the IQ of the result is to our individual "quality threshold".

This means (maybe) an 18-55 kits lens @50mm is equivalent to a 50/1.7 prime for a given purpose.
The 50mm prime can be proven to be better technically, but does it matter?
When the end result appears the same to the end consumer it does not matter.

[bigdazzler]

.... or .... we could all just go and take some photos ;)

I like to have a little bit of a basic understanding of how things work but I feel that sometimes we can get a bit too caught up in all this sort of stuff.

[Kym]

.... or .... we could all just go and take some photos ;)
I like to have a little bit of a basic understanding of how things work but I feel that sometimes we can get a bit too caught up in all this sort of stuff.

Sure!

But we do discuss a lot of gear etc. on AP and this essay at least brings come sanity to the comparision discussions.

I'm one of those who likes to know what under the hood and how it works - some don't care
- and in the end it does not matter as long as it works.
But for those of us who like to get into the guts of technology - its a good read.
(From one who built a 4 bit computer from basic logic gates in the 70's) :cool:

[bigdazzler]

yep fair enough too .... some people are much more technically inquisitive than others mate, no denying that :)

[reaction]

finally got thru it all, it's great info, never thought about that f2 on 4/3rds = f3.5 on APS = f5.6 on FX!
now when people ask why they shouldn't get a 4/3rds for serious amateur work, or comparing 2.8 lenses for different formats...