Moose Loc: North Carolina

I made the following inquiry to a friend, who is very knowledgeable about cameras, and received a response that I need help understanding. I'm hoping one of you can explain this to me in more simpler terms.

My Inquiry:
Many cameras, such as my point and shoot, have lens aperture settings of f2.8 and f8.0. What are the limitations of these lenses over a DSLR that have lenses with higher and lower f stops? I’ve had the Panasonic FZ200 and now have a Sony which has these lens aperture settings.

Response:
It's all to do with crop factor and sensor size. The fz200 has 5.4 times smaller diagonal compared to full frame camera. This means that the lens, although it captures the same light, it does so with an equivalent aperture 5.4 x lstgrtyin terms of the depth of field. So in effect the f2.8 lens on the fz200 is really about f13 on a full frame camera if you looked at the same images from each. F8 is nearer to f64. So you can see why there is so much depth of field with it. The other downside is the light gathered makes the sensor 5.5 times noisier than the full frame camera

jerryc41 Loc: Catskill Mts of NY

Get ready for many pages of responses.

The aperture is determined by a mathematical formula based on the measurements of the lens. All I care about is using large or small apertures as they are needed. I don't do math when I'm taking pictures. It's nice to know all of this, though, since it makes understanding cameras and their specs easier.

rmalarz Loc: Tempe, Arizona

The f-stop number is a ratio of the focal length of the lens divided by the aperture, or entrance opening. It has nothing to do with crop factor, digital, or film. It's a dimensionless number that simple expresses a ratio.
--Bob

mrpentaxk5ii

Some get into the technical aspects of photography and at times it's alot to take it, from my use of diffrent types of cameras I can say this much, my Canon G15 has a max apeture of F8, due to the small sensor it has great depth of field, this is both a blessing and a curse. as you go up in sensor size you get a greater control over DOF and a wider apeture range over that of a small sensor camera.

SS319

If you have a camera with a sensor size of, say 1/4 a full frame camera, the manufacturer will use a lens that is in the 10 - 12 mm focal length range. So a very small diameter lens will show up as a f/2.8 (maybe 4mm diameter in the lens). This setup will give you the same image as a full frame camera with a 40-50 mm focal length and for the same ISO, should require about the same shutter speed for the same scene. The only real difference will be the quality of the picture. If both the full frame and .25 sensor have the same number of pixels (?), the pixel area will be 4 times as large for the full frame camera, and thus the sample population will be 4 times greater, and the resolution should approach 16 times better.

Additionally, most P&S cameras have plastic lenses , some with remarkable index of refractions such that instead of a 4mm diameter lens, the camera may only have a 2.5mm diameter lens to yield the same equivalent light gathering capabilities of a 4mm f/2.8 lens. Most plastic lenses are cast, while all glass lenses are ground, but even the plastic lenses are polished. with larger Index of refraction, any flaws or inconsistencies in the plastic lens will degrade the image more than in a similar glass lens.

Limitations compared to DSLR with lenses with Apertures outside the f/2.8-8 range: even though the 2.5 high refraction has an equivalent f/2.8 aperture, the depth of field for this lens is as you would expect from a 2.5mm diameter lens with a 12mm focal length - about a f/4.8. So a full frame lens with a f/1.4 lens will be able to soften the background and yield a much shallower DoF for Portraits; Similarly, a lens with an f/16 - f/32 (or even f/48) will yield a very great DoF , at times making everything from 3 feet to infinity in focus. Additionally, with greater control over the aperture, the photographer has more control over his shutter speed and can stop a drop of an athlete's perspiration in space or can blur the water rushing over a Dam or waterfall to give a very soft image.

repleo Loc: Boston

In simple terms, he is saying you won't be able to get any bokeh and the shots will be noisier or grainier compared to a DSLR.

Brent Rowlett Loc: Atlanta, GA

Lenses with multiple focal lengths, i.e. 24mm-105mm will never yield the same quality sharpness of a dedicated lens like the 50mm, 85mm portrait, 100mm macro. Too many elements to contend with.

With multiple f-stops available, rule of thumb is to pick the sweet spot of the lens, generally the midpoint of the aperture range--usually f-8. For groups and a starburst on sun, lights etc. use f-11 or f-16.

When considering censor size, pick the big censor. I would buy a new camera and chuck that cell phone of a camera. The Canon 5DSr and Nikon 850 have the enlarged medium format censor, and the quality of print is amazing. I can print a 24 x 36 image out of the Canon 5DSr without enlarging. The new drones have the big censor now--difference between taking a picture with a cell phone and a DSLR. Absolutely no contest. The I Phone 7-10 would have a better camera than the one you are describing.

Moose Loc: North Carolina

Thank you all for taking the time to respond to my inquiry. I think I need to do more studying on the subject to fully understand it. Thanks again.

kymarto Loc: Portland OR and Milan Italy

Moose Loc: North Carolina

Thanks for that input. The article helps to explain things.

SteveR Loc: Michigan

From what I read, the article talked about equivalence in terms of field of view and depth of field, but not the amount of light gathered. F2.8 should be equal in light gathered from one set of lens and sensor to another.

HarryBinNC Loc: Blue Ridge Mtns, No.Carolina, USA

The "Resolution" of the two sensors (if both are 16 Megapixels) will produce the same size images on your monitor and in prints. The physical size of the sensor doesn't have anything to do with the pixel resolution that determines the output print size. Theoretically, if you are talking about 2 high quality cameras with quality lenses, you will have a hard time knowing which image came from which camera when viewing images at the same size on either a print or on a monitor if "equivalent" f-stops were chosen. The difference, if there is any, will be due to the "quality" of the respective pixels in terms of color accuracy, ISO "noise", etc. rather than the size of the individual pixels.

I apologize in advance if I misunderstood what you were saying above. It sounded to me that you were making the common mistake when comparing sensor sizes and equating them to film in that a negative film frame from a small format camera has to be magnified to produce an equivalent size print as a larger format camera, thus automatically degrading the resolution of the print from the smaller negative.
That doesn't happen in the digital world.

HarryB

PHRubin Loc: Nashville TN USA

Aperture is an indication of how wide the lens can open. The lower the number, the wider it is open. A wider lens lets in more light and so can operate in darker conditions. However, the wider the opening, the smaller the depth of field (the range of distances that are in focus).

At the other end, narrow openings have greater depth of field, need brighter subjects, and when the opening gets too small, introduces fringing which makes the image less sharp.

The smaller the sensor (compact camera vs DSLR) the smaller the opening for the same f stop. Consequently, fringing can occur on wider f stops on a compact.

kymarto Loc: Portland OR and Milan Italy

Equivalence means that because of the higher noise on a smaller sensor with smaller photosites, the same aperture will produce a noisier picture on a smaller sensor. So a 25mm f1.4 lens on MFT (which is 0.5x the size of a FF sensor) will give both the same angle of view AND noise as a 50mm f2.8 lens on a FF sensor, roughly speaking. So in this case f1.4 on a MFT lens is equivalent to f2.8 on a FF lens.

tdekany Loc: Oregon

For depth of field only.