Digital Cameras, a lie of omission.

Iron Flatline · Dec 17, 2007

And if you now print the various images captured with those kinds of crop factors onto 4x6 inch paper, of course the bird will appear bigger on the 4x6 inch print than the one made from the 1.3x or the 1x size sensor.

Iron Flatline · Dec 17, 2007

Another Link

Iron Flatline · Dec 17, 2007

... and one last one.

Now, check out how small a sensor can get.

The dark area is full-frame.

The red and blue (1.6x and 1.5x crop factor) are common Canon and Nikon sensor sizes.

The green (poorly-named) 4/3rd standard is Olympus/Leica/Panasonic

The little ones are in your typical Point & Shoot cameras...

Now imagine putting around 10 million pixel light sensors on each of these. THAT is why little sensors are noisier than bigger sensors.

Now go take pictures

RacePhoto · Dec 17, 2007

Iron Flatline said:
And if you now print the various images captured with those kinds of crop factors onto 4x6 inch paper, of course the bird will appear bigger on the 4x6 inch print than the one made from the 1.3x or the 1x size sensor.

Simply put. True. A 50mm lens is still a 50mm lens, no matter what you put it on. The end. Done deal.

However, not to leave things simple. If the full frame sensor is 6mp and the 1.6 sensor is 6mp. Both images will have the same resolution of 6mp. So it's not like using that useless and stupid digital zoom that some cameras have. :lol:

Now can someone explain the claim in the original message, that my 1.4 lens becomes a 2.8 depending on what camera it's on. That's not true. The amount of light a lens transmits does not change with the sensor size.

Because the cropped sensor image is using the center of the image that the lens is transmitting, it should be better (in theory!) because it's the center of the image and less likely to have the edge distortions that a full frame would have with the same lens. There are some possible advantages.

I never thought about that extra light bouncing around in my camera. Interesting.

Patrice · Dec 17, 2007

Iron has it right, good examples to explain the concept. Well done !
And Race Photo, the f1.4 you paid good money for is still and always will be an f1.4. You are correct when you say that one advantage of a cropped sensor is that you are only using the centre portion of the image circle, unless you are using a 'dx' lens.

Hubertus Bigend · Dec 17, 2007

Thanks, that was pretty helpful.

JIP · Dec 17, 2007

Dude you are sooooo obsessed with a dying medium!!. I started shooting film many years ago and was a very late convert I love printing B+W but see no sense in poisoning myself snd the environment when you don't have to. let it go man you will have to convert someday too you will not have a choice.

skieur · Dec 17, 2007

OK, what I have not noticed yet, is the following:

You use a 300 mm lens at 300mm on a full frame camera and take the shot.

You use 200mm lens on a 1.5 sensor camera with low noise at 300mm and take the shot.

What are going to be the specific quality differences between the two shots? Does the resolution in lines change and by how much? Does contrast, colour or dynamic range change and by how much? Would most people notice the difference between the quality of the two shots?

This is the most important part and the bottom line to this discussion, so let's get to the point and by the way I am not making any implications, I would simply like to hear the answers. :wink:

skieur

Helen B · Dec 17, 2007

If they are taken from the same point, the lens is focused at the same distance and the results are viewed at the same size the 1.5 crop sensor camera (ie the one with the 200 mm lens) will have greater depth of field.

Under the same conditions as above, as the lenses are stopped down the smaller sensor (shorter lens) camera will probably show diffraction effects before the larger sensor (longer lens) camera.

Best,
Helen

Note: Depth of field markings on a lens are designed for a particular format. If you are using a full frame lens on a camera with a smaller sensor, a good rule of thumb would be to use the depth of field markings for one stop wider for a 1.6x to 1.3x camera, and two stops wider for a 2x camera. For example, if you are using a lens marked for a full frame camera on a 1.5x crop camera and it is set to f/11, use the DOF markings for f/8. This assumes that the same sharpness criterion is applied in both cases. Like most depth of field issues, there are numerous ways of comparing depth of field. In some cases, such as diffraction-limited depth of field, the DOF is independent of format.

jstuedle · Dec 17, 2007

I have never seen the argument that a cropped sensor would change the maximum aperture of any given lens before. That argument simply boggles the mind. If that were so, a different and unique hand-held light meter would be needed for every size sensor, as well as 110, 35mm, 120, 4X5, 8X10 and all the other film formats since the start of photography. I intend no disrespect, but the concept is so wrong-headed, it's humorous.

RacePhoto · Dec 17, 2007

skieur said:
OK, what I have not noticed yet, is the following:

You use a 300 mm lens at 300mm on a full frame camera and take the shot.

You use 200mm lens on a 1.5 sensor camera with low noise at 300mm and take the shot.

What are going to be the specific quality differences between the two shots? Does the resolution in lines change and by how much? Does contrast, colour or dynamic range change and by how much? Would most people notice the difference between the quality of the two shots?

This is the most important part and the bottom line to this discussion, so let's get to the point and by the way I am not making any implications, I would simply like to hear the answers.

skieur

Too many variables. Why are you using a 200mm on one camera and a 300 on the other? How about the SAME lens on both, for starters. Your 200 is still a 200. I thought maybe the thread would get that point across. You are just getting the center of the image, of the full frame.

Then you need to specify the sensor resolution. I can have a full frame 4mp and a 12mp 1.3, which means the smaller sensor will be better.

What you might be trying to ask is, if you take the same photo, with the same lens, on a full size sensor and crop it to the same size as the 1.5 sensor, will there be a difference.

However when you crop the full frame, you may be getting the same lower resolution as the 1.5, because you are elimination the data from around the center of the photo.

Hey look. That's the same as the smaller sensor does. You are missing the data from the edges.

Here's another way to get the same effect. Print a photo at 4x6, now print the same photo on identical paper with the same printer. Then cut out a 3x5 print from the center. (example is not a perfect 1.5, 1.3 or 1.6, it's just for example)

The resolution, is identical. The quality is identical, everything is the same. That's what the sensor does. It CROPS the center of the image, compared to a full size sensor.

The crop factor works for sensor resolution too. A full size sensor, at 10mp and you crop the image down to the same size as a 1.6 crop 6mp sensor would produce, and guess what? You have a 6.1mp image.

I didn't know that the intentions behind this original message were to defend film and try to denigrate digital. I just thought i was someone who fell for the usual "sensor crop making lenses act like..." BS line.

Maybe I should have seen through it when the same message claimed that our lenses would become "glacially slow" which isn't true. And then the bouncing light and other loaded claims of lies of omission.

Sorry for being dense. I thought it was an honest question, not some film based, political agenda.

Garbz · Dec 18, 2007

What depth of field wise? Definitely not light wise think about it. The distribution of light around the sensor is equal. You crop the the middle of a f/1.4 ISO100 1/1000th image yes you won't get the same depth of field since now the focal length is longer but there's still f/1.4 ISO100 1/1000th amount of light covering each individual point on the sensor.

As for the scattering of light, look inside the front of the camera and use your almighty physics to help explain why this is definitely not a problem.

Bobby Ironsights · Dec 18, 2007

JIP said:
Dude you are sooooo obsessed with a dying medium!!. I started shooting film many years ago and was a very late convert I love printing B+W but see no sense in poisoning myself snd the environment when you don't have to. let it go man you will have to convert someday too you will not have a choice.

Dude, if my only choices were 35mm colour negative film, or 35mm colour digital, Id convert tomorrow, but I like B&W, and Im since moved on to large format, and in these areas digital is inferior. Im not into flogging a dead horse, and Im no Luddite. I dont drive a steam powered car, and use kerosene lanterns and an outhouse.

I'm not obsessed with a dying medium, I'm fascinated and excited by the artwork, and blown away by the extreme cost of large format digital scan-backs, and deeply saddened and disappointed by the inferiority of digital B&W.

jstuedle said:
I have never seen the argument that a cropped sensor would change the maximum aperture of any given lens before. That argument simply boggles the mind.I intend no disrespect, but the concept is so wrong-headed, it's humorous.

Yes, I was wrong.

I dont shoot digi, and I assumed that the common line I was hearing about a 50mm turing into an 85mm was truth. So I simply did the math, and came up with the affected f-number. It turns out I made a classic math mistake.and used a bad initial fact as my starting point, so I ended up in the wrong place Which I explained in the very beginning of the post, five hours before you posted this.

Are you just having fun heaping condemnation on someone who made an honest mistake or what? Dude, that's just not nice!

RacePhoto said:
I didn't know that the intentions behind this original message were to defend film and try to denigrate digital. I just thought i was someone who fell for the usual "sensor crop making lenses act like..."

Sorry for being dense. I thought it was an honest question, not some film based, political agenda.

It wasnt political, I was fooled by the 50mm=85mm crap, and the extra light bouncing around thing, is a real effect, it happens when using roll film on a large format back, a problem film users have to contend with too.using a format thats too small for the lens design. Its not a new problem, and I dont contend that its unique to digital.

I'm also not a film-nazi. I chose my 35mm lens collection (Canon EF mount) based upon the assumption, that when full frame sensors come down in price, or I leave Univ. and am gainfully employed, that I'll be buying one.

Helen B · Dec 18, 2007

Garbz said:
...
You crop the the middle of a f/1.4 ISO100 1/1000th image yes you won't get the same depth of field since now the focal length is longer...

The focal length does not change when you crop. The degree of magnification required to make the print changes. That is what changes the depth of field: the smaller image has to be magnified more to get the same size print, therefore the diameter of the acceptable circle of confusion reduces. 'Print' in this case being used as a general term for the final output, the comparison being between two images made with the same lens.

Best,
Helen

shundaroni · Dec 18, 2007

Welcome to the crow feast. You can't throw down a debate gauntlet using condescension (especially that "at least I thought it would" line) and expect people to be sympathetic when you fall on your face. Such is the price of forum snobbery. I say sit back, tie on your bib, and learn to like the taste of dark fowl. At least for the next day or so.