What is Focal length, Sensor size in photography and why is it matters?

The intention of this article is to dig out the relationships between focal length of the lens and the camera’s sensor sizes and how does the both affects the framing independently.

I have made a simple illustration diagram below, which depicts how does the light enters from the scene to the sensor/film.

Focal Length-Photography-Sensor-Light entryImage a. – Light travelling path inside a lens and camera body from the scene. x is the height of the sensor(part of the camera), b is the focal plane(principal)- this always happens inside the lens, z is height of the frame (photograph’s vertical measurement in landscape mode), y is the focal length which is usually mentioned on the lens.

Focal length(y) is the distance between the sensor (a) and the focal plane (b) where the light rays converge to form a sharp image of an object to the digital sensor.

Now, the frame you see via the viewfinder will change, if you adjust the Focal length which is possible in zoom lenses. The same is not possible in prime lenses since the focal length has been set in the factory itself while manufacturing, in such a way that it cannot be changed. The prime lenses are made purposely for high quality at a lesser price comparatively with a zoom lens in that focal length.

Conversely, it is also possible to change the frame by changing the size of the sensor. But the sensor has been fit inside the camera while manufacturing in the factory itself and it cannot be changed by wish on the field. But you can use two different cameras having different sensor sizes as one may wish.

Now we have understood that, if we change the size of the sensor (x) or the focal length (y), in both the ways the frame will get changed.

The ranges of available lenses in the market with different focal lengths are beyond listing thus I am not getting into that.

Sensor sizesImage b – Scale of the other smaller sensors with respect to the Full frame sensor. The FF sensor size is 36mm × 24 mm. For the sake of understanding, we here discuss about the vertical  measurement(x).

The smaller the sensor sizes, the field of view gets narrower. That is, if “x” gets smaller, “z” also becomes smaller Assuming that the “y” is same in both the cases. Conversely, if “x” gets bigger the field of view (z) also gets wider.

The advantages and disadvantages of choosing which sensors (cameras) have been briefly explained here in my earlier article.

The crop ratio has been established in the industry with reference to the 35mm film sensors. 35mm width sensors are the reference one and the crop factor for those sensors is 1.00. Other sensors are classified by the crop factor with respect to 35mm sensors (1.00).

Crop factor is the ratio of the dimensions of a given sensor’s imaging area compared to the 35mm sensor’s imaging area (full frame sensors in common). If a sensor’s crop factor is more than 1(APS-C sensors), the image area will be less by that ratio. Conversely, if the crop factor of the camera is less than 1(medium format cameras), the image area will be more by that ratio.

For instance, if a camera’s crop ratio is 1.60 and you have mounted 85mm prime lens, what the camera sees is the view of 136mm (85mm × 1.60) not what is written on the lens. If the same 85mm lens been mounted on a medium format camera with 0.50 crop factor, what you will be seeing is 42.5 mm (85mm × 0.50) focal length view.

Sensor sizesImage c – Dimensions of the different sensors fixed in different cameras and the respective crop ratios.

The focal length written on the lens is true, only if it is mounted on 1.00 X crop factor sensors (full frame cameras). If you are mounting it on non-full frame cameras, you should multiply the crop factor of that camera to get the actual focal length.

I hope, I have covered all the necessary topics which are required to understand the focal length, sensor sizes and how does both affects what you see in the viewfinder. Have I missed something? or the article been helpful to you, do drop a comment and let me know.

Cheers & Happy Photographing.

“R” in Lr.

♦  The moment you Press ‘R’ from whichever the module you may be in Lightroom, you will be taken to develop module with crop tool activated, and the “rule of thirds” overlaid on your image. Check the screenshot Fig – 01 below.

ImageFig – 01 Crop tool activated and Rule of thirds overlaid on your image.

♦  Now it is your turn to select an aspect ratio and give a try. Select an aspect ratio from the drop down menu in the crop tool bar (the tool bar works on demand based, you can’t see unless you activate the crop tool), once you selected the aspect ratio the size of overlay will change on the image. Now drag the overlay as you wish – towards your right, left, up or down – literally recompose your shot by placing the overlay in relation with the prime subject in the photograph. Press enter or click close or press ‘R’ once you are done. Check the screenshot Fig – 02 below.

ImageFig – 02 Aspect ratio selected as 1 × 1 and encircled in red.

And note the remaining portion apart from the potential image area is dim already, which makes decision-making as an easy one.

♦  How about adjusting your image to perfect horizon or to perfect vertical.! There are two options to do it in Lr, either by clicking the spirit level symbol in the tool bar, click the spirit level (encircled in the screenshot Fig – 03) and draw a straight line on the horizon or when the crop tool is active, keep the cursor out from the image area and drag up and down, there will be more grid lines overlaid (which will act as reference lines) as you move the cursor and you will be in a better position to evaluate your image to make it perfectly horizontal or vertical.

Image

Fig – 03 Spirit level tool encircled in red.

♦  Want to make a free form crop, with your own aspect ratio !. Click the lock symbol to unlock and to make it free form, drag your cursor inside the image area from one top corner to another diagonally opposite corner to make your own crop. Check screenshot Fig – 04

Image Fig – 04 Lock symbol encircled.

♦  When you make lens profile corrections, possibilities are there to include the corrected portion (the edges mostly). To avoid that click constrain to warp, as in the screenshot. Once you make constrain to warp on, the image will be cropped after the correction or it can be applied alternatively in the lens correction panel also. Check screenshot Fig – 05

ImageFig – 05 with Constrain to Warp check box encircled.

Here is the most interesting part in this tool.
♦  Want to see how your image will look according to different compositional rules, Lightroom comes very handy here. Your crop tool is activated by pressing “R” and the rule of thirds is overlaid, at this juncture press “O” and watch the image area, the different compositional rules will be overlaid as you press “O” repeatedly. These options are in Lr to make your photograph a much better than you thought while clicking the shutter. Look at the screenshots below.

ImageFig – 06 Screenshot with diagonal rule of composition overlaid

ImageFig – 07 Screenshot with Rule of triangle overlaid.

Image

Fig 7-a. Screenshot with Rule of triangle applied in a reverse manner (read further below on how to activate that).

ImageFig – 08 Screenshot with Golden rule overlaid

ImageFig – 09 Golden spiral rule overlaid.

There are total five no. of rules can be displayed and applied to your photograph in Lightroom.

a. Rule of thirds

b. Diagonal rule of composition

c. The golden triangle

d. Golden ratio

e. Golden spiral

Out of these five rules “The golden triangle” and “Golden spiral” can have a different versions like in Fig – 7.a, which can be activated by pressing and holding Shift along with press “O”. You can do the same for Golden spiral rule too, it has more versions. Check out and comment below, what do you feel about that.

I wish Adobe Lightroom add “Rebatment of rectangle” too in to the rules list in their further releases, it is also interesting one. The light intensity of the rule lines can be controlled by pressing and holding “Ctrl” key. Apply the rules together with different aspect ratios, the options are too many to make a better photograph.

Cheers. Hope you enjoyed this article. If so share it with your friends, they might also like as you did.

Y Processing.

As a photographer, it is not uncommon to come across these questions quite often; “Is post processing necessary?” “Why do you shoot in RAW and then convert it?” “Should I shoot in RAW or JPEG?” This blog post is trying to answer these questions about processing.

“A photograph is made in the camera, not in the computer”; while this statement remains true, in this digital era, a computer and camera go hand in hand. Processing (Computer) is all about bringing out the best from the RAW data (Picture in RAW format) your camera recorded. This is literally impossible with JPEG.

Before getting into the real subject, a basic knowledge of how your camera captures images in RAW and jpg, will make things easier.  Firstly, RAW is not an Image format; it is the data that is seen by the camera sensor which is recorded into the memory medium. jpg, however, is altogether different. The sensor sends all the RAW data to the processor and the processor converts it into jpg format with the preloaded instructions based on the time the image was captured and exposure value. The important part to be noted here is that the processor discards the rest of the data after converting it to jpg. Remember, the instructions preloaded by the manufacturers are not specific to the images; it is generic and every correction made by the processor on the image like sharpening and contrast, such as, are global and not local. And the reason you get a fairly neat image is because the instructions are based on 10000+ images shot by the various top photographers then across the globe.

This is the very first reason capturing a picture in RAW and post processing is important to bring out the best of the camera.

The second reason is the ability to process the image. Processing here includes White balance correction, exposure adjustment, contrast correction or boosting, correct to the true colors, sharpening, color cast correction etc. The extent to which one has to process the picture is entirely a personal choice. It is your picture, so you should define how it looks, and tweaking around with the above given parameters is acceptable, in all contexts.

It is very important to note that post processing and image manipulation are altogether different. I don’t consider manipulation as a part of photography processing. By manipulation I mean the inclusion or exclusion of some or more parts of the image. The reason one should not manipulate the image is that, I feel that he/she is an expert photoshoper but not a photographer.

Photography is an art form and processing is also part of that very art. Learn it; there are lots of websites out there. I use Light room for my all processing requirements with few plug-ins like Nik collection, Enfuse, Mogrify, The Fader etc. I strongly say that photography and processing is equally important task by its very nature.

I can very strongly vouch that Photography and post processing are equally important tasks, especially in today’s digital era of photography.

Again, all this is a personal choice. Kenrockwell, a very technically sound photographer takes his images in JPEG only. So the choice is entirely yours.

Keep clicking,

Cheers.

Aside

What is photography?

 

I think this is high time that the above question needs to be answered.

Answering straight to the question

  1. If you are able to tell a story /make the viewer to stare at the image for a while / frame an idea, show something really beautiful (Street,Travel)
  2. If you are documenting something (Wildlife, Poverty, Illegal acts, War)
  3. If you are making a concept  (Conceptual , Creative Ads)
  4. If you are showing off something which is not possible to see by the general naked eyes (Macro, Aerial, Underwater)
  5. If you are making something really beautiful (Landscapes, Events, Portfolios,Fashion, Products, etc.,)

1. And why street is on the top

Nothing is in your control; you and your camera only, yet you put an idea, piece of intelligence there between the four lines. Not lighting, not the subjects, nothing is in your control.

2. Here is why Wildlife, War, Poverty – Humanity

You have less control, much more risk in shooting wildlife, sometimes fatal, compromising on your comfort level staying in some remote places where there are no humans, no food, no water yet you loved your camera and went for it, recording the wildlife’s unseen actions and unseen lives.

Likewise you have risked your life for documenting Poverty, Illegal acts, War to bring attention of the common people and governments, activists.

*It is really difficult to classify these two titles in to first & second position, yet I have taken a stand and given importance to photographical point of view.  Do not be very sympathetic, ideas have made us evolved from the invention of stone wheel till cryogenic engines.

3. Conceptual Ads, Creative awareness ad Photography

Everything is under your control, but you have put your intelligence there.

4. Macro, Under water, Aerial Photography

You use so many equipments to capture that outstanding shot, much more planning, taking risk etc.,

5. Landscapes, Events, portfolios

Photographing landscapes is nothing than to take a very beautiful photograph, purely personal satisfaction. Events, portfolios, products all are commercial. Hence last.

Just because you bought an inexpensive or expensive camera, it does not mean that you have to take snapshots. Start respect the master piece of engineering, it will start giving you photographs. Believe me. Start learning, Photography is fun, it is happiness.

Here are few links where either you will learn something or you would be astonished by the masters.

Few iconic images been analyzed by experts here (Check out all the four parts)

Check this master’s images here (Outstanding photographs can be in colour as well)

The above two links are just sample, there are so many masters, start searching.

By writing this article I am not trying to establishing myself as a great photographer or master but I am trying to be one by each time I press the shutter button and most importantly I am learning by day by day. I have taken for granted to write this article assuming that, I am a photographer because one of my photographs went to 2 stories height of printing and one other image is being displayed in an international creative online gallery. Even when these two images are not selected for any display, I would be writing this because I understand what photography is. I am doing wedding photography as my profession.

Full frame & APS-C sensors why and why not.

Full frame is derived directly from 35mm films. The sensor size is 35mm width as in films.

The advantage of having a full frame is

a)    You have got around 2.5 times more surface area on the sensor than in an APS-C sensor; it means more photo sites in the sensor which directly leads to capturing more details.

b)    By the very nature of the sensor you can shoot up in high ISO without any significant noise.

c)    The lens focal length will shoot what exactly it shows when it is mounted on a full frame sensor. (details below)

d)    You want to take a shot at f 1.8 in a full frame; you get 1.8, but in APS-C you get 2.88 and so on. (details below)

For instance you shoot in 200 mm zoom on a full frame camera you get exactly what it is in 200 mm, but in a APS-C (1.6 crop factor) actually you get 320mm zoom (1.6*200), it could be an advantage of using APS-C for some zoom shots. When you want to take a wide angle shot you actually zoom in a bit. In that case you definitely need a full frame camera and that too, too many details in a wide angle shot, without a doubt you need it.

The shot you take on f 22 in a full frame is not the same when you take the very shot in f 22 in APS-C. To get the shot equivalent to f 22 in FF you have to change the f no. to 14 in APS-C.

Image

Advantages of APS-C sensors

a)    You zoom in according to the extra crop factor, say if the crop factor is 1.6 multiply your focal length by 1.6 (as mentioned above), without any extra zoom lens.

b)    The cost of the APS-C sensor/camera is far less than FF. (Details below)

c)    A very good one for starters.

Why a FF sensor does cost much than an APS-C?

Sensor is made of Silicone wafer with other technical parts in it. The silicon panel comes in a size where APS-C sensors can be cut without much wastage. Whereas lots of wastages in cutting in to FF sensors. So the manufacturers want to make the lost money in wasting the wafers. (I strongly believe they will be recycling the waste portions)

Conclusion

a)    If you are a starter you do not have to buy a FF camera, APS-C is far better for learning.

b)    If you are a wildlife photographer, you buy an APS-C high end camera (say canon 7D) you get 1.6 converter attached to it by its very nature.

c)    If you are high end fashion photographer and your photographs are going to print often, better you own a FF apart from having some L lenses.

d)    If you are a night bird; you have to take a FF camera. APS-C cameras are very bad for lowlight, night photography.

e)    This above list is not exhaustive.

Thanks for reading, If you find useful do comment and share. If you find mistake do notify, will modify it. I do make mistakes.

Navaneethan

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